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Abstract

Chalk flows are flow slides that develop under certain circumstances from falls in chalk slopes. They are characterized chiefly by the mobility of the debris, which can run out over near-horizontal surfaces for as much as five to six times the slope height.

After a brief account of the stratigraphy and extent of the Upper Cretaceous exposures of northwest Europe, chalk flows are described in outline, classified, and set in context with other types of flow slides. The relevant morphological parameters are defined. The incidence of chalk flows on the coasts of northwest Europe is outlined. Such failures occur in England, to a small extent in Sussex but predominantly in southeast Kent, in France from just north of Cap de la Hève to Ault in Haute-Normandie, in Denmark at Møns Klint, and in north Germany at Jasmund, in the northeast of the Isle of Rügen.

It is shown that these flows occur only in soft chalks of high porosity (>~40%), in cliffs higher than ~30 m. Their mobility is inferred to derive principally from high excess pore-water pressures generated by a process of impact collapse in the saturated or near-saturated metastable soft chalk as it impacts onto the shore platform. Where earlier saturated colluvium is present on this platform, its undrained loading by the falling debris probably also plays a role, as does the presence or absence of seawater. Desirable further research is outlined, and the hazards posed by chalk flows are described.

Introduction

In the study of the chalk fall at Joss Bay, Kent (Hutchinson, 1972), the chief aim was to carry out a reliable back-analysis in order to estimate the average shear strength mobilized at failure. Subsequently, partly through a consulting assignment that posed the question as to how close under the face of an abandoned chalk quarry it was safe to locate a new factory wall, partly through awareness of the remarkable “Great Fall” of 1915 in Folkestone Warren (Osman, 1917), and partly in response to the increased interest in the assessment of landslide hazards in general, attention was directed to a study of the runout of chalk falls. The results are summarized herein; the essentials were presented at a lecture to the Geologists’ Association in London on January 13, 1988.

COASTAL CHALK OF NORTHWEST EUROPE

A broad definition of chalk as a coccolithic limestone was given by Hancock (1986), although Mortimore (1990) noted that in very hard chalks, such as the Ulster White Limestone of Northern Ireland, the original coccolithic material may be rendered virtually indistinguishable through diagenesis. Northwest Europe is taken here to include the coasts of Great Britain and of mainland Europe from the mouth of the Seine in France, through Belgium, the Netherlands, northwest Germany, Denmark, southern Sweden, and northern Germany as far east as the mouth of the Oder. The Upper Cretaceous is broadly synonymous with the chalk over most of this region, although nonchalk facies are present in a few places. The extent of the Upper Cretaceous outcrops in northwest Europe is outlined in Figure 1, and its stratigraphy is summarized in Table 1.

Figure 1.

Extent of Upper Cretaceous outcrop in northwest Europe (after Choubert and Faure-Muret, 1976).

Figure 1.

Extent of Upper Cretaceous outcrop in northwest Europe (after Choubert and Faure-Muret, 1976).

Table 1.

Stratigraphy of the Upper Cretaceous (After Birkelund, et al., 1984)

Stage
Maastrichtian
Campanian
Santonian
Coniacian
Turanian
Cenomanian
Stage
Maastrichtian
Campanian
Santonian
Coniacian
Turanian
Cenomanian

Note: Relationships to the earlier, now informal terminology of Lower, Middle and Upper Chalk are shown subsequently in Figure 36.

Throughout this sequence the lithology appears in a broad sense to be remarkably uniform, but in detail it exhibits significant variations. For the purposes of this chapter, following Clayton (1983) and Mortimore and Fielding (1990), dry density (γd) or porosity (n) is taken to be the most convenient parameter to express the lithology and texture of chalk in engineering terms. The chalk hardness classification used is generally that of Mortimore and Fielding (1990), based on values of dry density (kN/m3) and ranging from very hard (>19.12), through hard (19.12−17.65), medium (17.65−16.67), soft (16.67−15.69), very soft (15.69−15.20), and extremely soft (<15.20).

The main in situ chalk outcrops that form significant coastal cliffs in northwest Europe are in Northern Ireland, eastern and southern England, northwestern France, and southeastern Sjaelland, Denmark. There are also important glaciotectonically disturbed exposures at Møns Klint on the east coast of the Isle of Møn in southeastern Sjaelland and on the eastern side of the Isle of Rügen in north Germany (Fig. 1). Between northwestern France and these Danish and German exposures, the surface of the coastal chalk is generally far below sea level (Dassargues and Monjoie, 1993; van Rooijen, 1993; Nygaard, 1993), except over some salt domes (Schoenfeld and Grube, 1990). The chalk crops out in the base of the Heligoland cliffs (J. Schoenfeld, GEOMAR, 1996, personal commun.) and forms low cliffs in northern Jutland, in western Møn (Surlyk, 1984), and on the southeast coast of Bornholm (Rasmussen, 1979a), but I know of no significant failures in these outcrops. Upper Cretaceous rocks, containing little or no true chalk, occur in the southernmost provinces of Sweden. Along the coast they generally are below sea level and where exposed form a low, cliffless shoreline (Gustafsson, 1993; J. Bergström, Geological Survey of Sweden, 1988, personal commun.).

CHALK FLOWS OF NORTHWEST EUROPE

Definition, classification, and terminology

In Hutchinson (1984, 1988), the term “chalk flow” was proposed for a flow slide developing from a chalk fall. There is some precedent for the term chalk flow in German; “Kreidefluss” and “Kreidestrom” were used by Hurtig (1959a) to describe the Rügen failure of 1958. The term “flow slide” is used here in the sense of Casagrande (1936), Bishop (1973), and Bjerrum (1971), in which a collapse of metastable saturated or nearly saturated soil and/or rock structure leads, through undrained loading, to the generation of high excess pore-water pressures, which give the essentially cohesionless debris a high temporary mobility. Photographs of the chalk flow of December 31, 1911, at Abbot's Cliff were shown to the late A. Casagrande, who had no doubt that this was a form of flow slide.

I (Hutchinson, 1995) emphasized that chalk flows are part of a wider family of flow slides (outlined in Table 2). The materials involved all have a high porosity (low dry density) and a zero or very low content of clay minerals. They range from being completely cohesionless to possessing a degree of cohesion, e.g., through cementation. The degree of disturbance needed to bring about the collapse of structure and the generation of high excess pore-water pressures tends to increase with the degree of cementation.

Table 2.

Members of the Flow Slide Family

Loose sandSubaqueousCohesionlessIncreasing disturbance needed to generate high + Δu
    Natural, sea bed (Zeeland coast)
    Artificial, hydraulic fill (Fort Peck)Subaerial
Loose debris
    Natural, scree (Modalen)
    Artificial waste dumps (Aberfan, Jupille, etc.)
Quick claySome cohesion or cementation
    Scandinavia and Canada
Weathered igneous rock
    Kaolinite (Cornwall), pumice, etc.
Loes
    Khansu Province (China)
    Dushanbe (Tajikistan)
Soft chalk
    Kent and northwest Europe
Loose sandSubaqueousCohesionlessIncreasing disturbance needed to generate high + Δu
    Natural, sea bed (Zeeland coast)
    Artificial, hydraulic fill (Fort Peck)Subaerial
Loose debris
    Natural, scree (Modalen)
    Artificial waste dumps (Aberfan, Jupille, etc.)
Quick claySome cohesion or cementation
    Scandinavia and Canada
Weathered igneous rock
    Kaolinite (Cornwall), pumice, etc.
Loes
    Khansu Province (China)
    Dushanbe (Tajikistan)
Soft chalk
    Kent and northwest Europe

Note: Table after Hutchinson (1995). All involve generation of high + Δu (liquefaction) produced by collapse of metastable, saturated or near-saturated structure in all or part of the mass (largely after Hutchinson, 1988)

The parameters and symbols employed to describe the morphology of the chalk flows described here are given in Figure 2 (based on Hutchinson, 1988). Throughout the following, a nominal 3 m is generally added to the estimated elevation of the cliff top above mean sea level to allow for the slope of the shore platform in arriving at approximate H values. Failures not involving chalk flowing are included where relevant.

Figure 2.

Plan and section defining morphological parameters of chalk falls and flows. Fahrböschung = tan−1 H/L; W = width of scar; Wd = max. width of debris, forumla = average width of debris; h = cliff height; H = overall height of failure; R = reach; L = overall length of failure, and forumla = average thickness of debris.

Figure 2.

Plan and section defining morphological parameters of chalk falls and flows. Fahrböschung = tan−1 H/L; W = width of scar; Wd = max. width of debris, forumla = average width of debris; h = cliff height; H = overall height of failure; R = reach; L = overall length of failure, and forumla = average thickness of debris.

The following arbitrary classification is used to indicate the degree of mobility of the various chalk flows: low, with length/height (L/H) between 1.3 and 2.49 (0.77 > H/L > 0.40); moderate, with L/H between 2.5 and 3.49 (0.40 > H/L > 0.29); and high, with L/H >3.5 (0.29 > H/L). Features with estimated L/H values < 1.3 are neglected.

Although the following review is undoubtedly incomplete, it is a useful outline of the incidence and nature of chalk flows in northwest Europe. It should be emphasized that in many of the references, slide dimensions and volumes are only approximate and are commonly exaggerated.

INCIDENCE IN GREAT BRITAIN

The main cliffed coastal outcrops of Upper Cretaceous strata in Great Britain are in Northern Ireland, Yorkshire, Norfolk, Devon, Dorset, Isle of Wight, Sussex, and Kent (Fig. 1). As shown later, in Northern Ireland the chalk is significantly harder than elsewhere, essentially a limestone, because of diagenetic recrystallization of calcite in the original pore spaces (Wilson, 1972). The Yorkshire and northwest Norfolk chalks are very hard and those of Devon, Dorset, and Isle of Wight are generally hard to very hard, the latter partly through tectonic deformation (Jones et al., 1984). In these hard chalk areas, although cliff heights reach >100 m, no reports of chalk flows have been found.

Of the three remaining areas, Sussex chalks range predominantly from hard to soft and Kent chalks are mainly from medium to extremely soft. Norfolk chalks, excluding those in the northwest of the county, occupy an intermediate range. Chalk flows in Britain occur overwhelmingly in Kent, with a few cases in Sussex (Fig. 3), and both these areas are described in detail herein. In Norfolk, the soft chalk cliffs in the northeastern part of the county are formed of glacially transported masses of predominantly lower Maastrichtian chalk (Peake and Hancock, 1970), related to those described from Denmark and north Germany, but the exposures are of restricted size and no chalk flows have been reported.

Figure 3.

Key map of southeast English and northwest French coasts.

Figure 3.

Key map of southeast English and northwest French coasts.

Sussex

In Sussex, the main chalk cliffs occur where the southern limb of the Wealden anticline, the South Downs, is exposed by marine erosion along part of its south side, in a predominantly strike section. The dip is generally gently south. Significant coastal chalk cliffs (Santonian-Campanian) (Mortimore, 1986) commence in the west at Black Rock, Brighton, where an abandoned interglacial cliff meets the present cliff line. Cliff falls in Brighton occurred in 1734 and 1749 (Howell, 1874) and in a storm on November 29, 1824 (Mantell, 1833; Walcott, 1859). None of these early accounts mention runout. A summary of the incidence of major chalk falls and flows on the Sussex coast is given in Figure 4.

Figure 4.

Incidence of major chalk falls and flows on coast of Sussex, England.

Figure 4.

Incidence of major chalk falls and flows on coast of Sussex, England.

The Santonian-Campanian chalk cliffs extend for 12 km from Brighton to Newhaven (Figs. 3 and 4), and are generally ~25–45 m high. Only moderate falls, with apparently no flow sliding, are reported from the western 9 km of this length. The largest known is that of February, 1891, before construction of the present sea defense works, which involved ~10 × 103 t of chalk and broke the cliff-top road (Geikie, 1903; Reynolds, 1932). In the eastern part of this length, probably in Friars Bay where the cliff elevation rises to above 50 m (Fig. 4), Rowe (1900, p. 338) reported a great fall of chalk in 1899, but gave no information on runout. Just west of Newhaven, the chalk cliffs are capped by a small Eocene outlier.

East of Newhaven is the valley of the River Ouse and the town of Seaford (Fig. 4). Between there and Cuckmere Haven is a 3 km length of Coniacian to Santonian chalk cliffs (Mortimore, 1986), culminating in Seaford Head with an elevation of ~85 m. In 1850 the cliff there was blown down by mines to form a rock groyne, with the object of preventing shingle being carried out of Seaford Bay by the eastward littoral drift, thus checking marine erosion at Seaford (Anonymous, 1850; Burgoyne, 1851; Frome, 1851). Denudation of the beach there had probably resulted from the work of improving Newhaven Harbour. The site chosen for the explosion was ~4.5 km east of the mouth of the River Ouse. The mines were placed in a gallery ~20 m landward of the cliff foot and ~20 m above mean sea level (Fig. 5). The charges of gunpowder, two of 5443 kg in the gallery and three of 1272 kg in the vicinity of the eventual rear scarp, were exploded at about 3:10 p.m. on September 19, 1850. In the event, only the two main charges, totaling 10 886 kg, exploded. The coastwise length of cliff involved was ~135 m, so the active charge amounted to ~81 kg/m. The volume of debris thrown down was calculated to be ~153 × 103 m3. It projected initially ~91 m beyond the cliff foot, giving a maximum L value on the east side of 121 m. The corresponding H value was ~68 m; the L/H ratio (Fig. 2) was ~1.78. A smaller natural fall at the same site a few days earlier had an L/H ratio of 0.76. According to Lower (1855), the experiment was not successful, the debris being largely washed away after a few high tides.

Figure 5.

Sections of artificially induced fall at Seaford Head, Sussex (most westerly of three sections, giving maximum L/H. after Burgoyne, 1851). HWL, LWL = high, low water level, respectively; MSL is mean sea level.

Figure 5.

Sections of artificially induced fall at Seaford Head, Sussex (most westerly of three sections, giving maximum L/H. after Burgoyne, 1851). HWL, LWL = high, low water level, respectively; MSL is mean sea level.

A natural fall at Seaford Head took place on July 15, 1986 (Anonymous, 1986). A section of the cliff more than 90 m long and 15 m wide fell away, taking part of the rough on the 15th fairway of Seaford Head golf course. A fall to the west of Hope Gap killed a woman in September 1908 (Young, 1910). In neither of these cases is there any information on runout. A photograph of a further fall in this length of cliff in the late 1980s is shown in Figure 6. The debris forms a talus at an inclination of ~30°, showing no evidence of having flowed.

Figure 6.

View of fall below Seaford Head, Sussex, in late 1980s (photo by Alan Stephens).

Figure 6.

View of fall below Seaford Head, Sussex, in late 1980s (photo by Alan Stephens).

Between Cuckmere Haven and Birling Gap is the 3.5 km length of near-vertical chalk cliffs known as the Seven Sisters (Fig. 4). This is formed through the truncation by the coast of a series of dry valleys, and ranges in elevation between ~25 and 80 m. Stratigraphically it consists of Coniacian and Santonian chalk (Mortimore, 1986). A large fall in this length on April 13, 1914 (Anonymous, 1914; Harris, 1943) at Went Hill, the most easterly of the Seven Sisters, had a (low) estimated L/H value of between ~1.5 and 1.6 (R.B.G. Williams, University of Sussex, 2002, personal commun.). A further, more massive cliff fall, involving an estimated 266 × 103 m3 (500 × 103 t) of in situ chalk, occurred at Baily's Brow (the sixth Sister from the west) in 1925 (Castleden, 1982). Smaller falls took place near Birling Gap in 1958 (May, 1971). There is no information on the behavior of the debris.

From Birling Gap to Beachy Head (Fig. 4), the Turanian and Coniacian chalk cliffs (Mortimore, 1986) rise, generally nearly vertically except in the east, to ~160 m above sea level at Beachy Head (Fig. 7). The present Beachy Head lighthouse, completed in 1902, is on the chalk shore platform ~165 m seaward of the base of the cliffs (Trinity House Lighthouse Service, 1979, personal commun.), nearly 1 km west of the highest point of the head. Marine erosion along this length has intensified since the early years of this century because of diminution of the beach (R. Gilbert, local resident, 1979, personal commun.).

Figure 7.

View of Beachy Head and lighthouse on June 12, 1975 (Cambridge University Collection of Air Photographs; copyright reserved).

Figure 7.

View of Beachy Head and lighthouse on June 12, 1975 (Cambridge University Collection of Air Photographs; copyright reserved).

On February 25, 1813, a large chalk fall took place at Beachy Head. The vicar of East Dean was viewing the prospect from there when he perceived the ground to move under his feet and discovered at the same moment a chasm developing behind him. He immediately stepped over the chasm. A few minutes later, the cliff fell with a tremendous noise onto the beach below. The ground lost at the cliff top extended ~91 m along the coast and 21–24 m inland. The volume of debris was computed to be ~235 × 103 m3 (Anonymous, 1813; Mantell, 1833; Webster, 1814). No direct details of runout were given.

One March morning, about the year 1848, Monkey's Cliff, a promontory just west of the highest point of Beachy Head, fell at ~6:00 a.m. (Bourdillon, 1884). It nearly killed two coastguards on the beach. One saw “the whole face of the cliff fall bodily forward … just as you may see a wave break on the shore.” The debris (E1, Table 3; Fig. 4) ran far out to sea and remained there for years, so that grass grew upon it. It acted as a natural groyne, preventing the eastward movement of the shingle and thus exacerbating marine erosion toward Eastbourne. Eventually, the Commissioners of Pevensey Level had the larger blocks blown up, to accelerate the washing away of the debris by the sea, but its effects as a groyne were felt for many years after. The coastguard also reported that, at the cliff top, the scar of the fall extended 155 paces (~140 m) along the cliff and encroached ~10 m beyond the former cliff-top path (possibly ~15 m beyond the former cliff edge). Because the cliff there approaches an elevation of 145 m, the volume of in situ chalk involved was probably of the order ~150 × 103 m3. The night patrol stood upon this point of the cliff only a few hours befor0065 it fell and observed no premonitory signs. Another heavy landslide in this vicinity in March 1853 was reported by Beckett (1929). Figure 7 suggests that the larger falls are associated with deeply cutting joints.

Table 3.

Most Mobile Chalk Flows on the Sussex and Kent Coasts

Chalk flow and numberApproximate (Fig. 2)Approximate L/HDate and location
L (m)H (m)
Sussex
E1Debris formed natural groyne?1848 Monkey's Cliff
Kent
E26281504.191915 Folkestone Warren
E3Debris ran out over beach?1877
E4Debris ran well out to sea?1910 Abbot's Cliff
E54711313.601911
E6Debris formed natural groyne?pre-1769
E74421453.051988
E8 (blasted)4701223.851843 Round Down
E9An immense fall?1772 Shakespeare Cliff
E10>36689>4.111912
E11An extremely large fall?1897
E12Debris formed natural groyne?1834
E13Debris formed natural groyne?pre-1767
E14Debris formed natural groyne?1690–1710
E15 (3 cases)Debris formed natural groyne?1760–1774 Dover Cliffs
E16288933.101910 South Foreland
E17405685.961970 Saint Margaret's Bay
E18R = 366??pre-1895
E19410795.191905
E20268833.231910
E21Larger than 1905 chalk flow?1870
Chalk flow and numberApproximate (Fig. 2)Approximate L/HDate and location
L (m)H (m)
Sussex
E1Debris formed natural groyne?1848 Monkey's Cliff
Kent
E26281504.191915 Folkestone Warren
E3Debris ran out over beach?1877
E4Debris ran well out to sea?1910 Abbot's Cliff
E54711313.601911
E6Debris formed natural groyne?pre-1769
E74421453.051988
E8 (blasted)4701223.851843 Round Down
E9An immense fall?1772 Shakespeare Cliff
E10>36689>4.111912
E11An extremely large fall?1897
E12Debris formed natural groyne?1834
E13Debris formed natural groyne?pre-1767
E14Debris formed natural groyne?1690–1710
E15 (3 cases)Debris formed natural groyne?1760–1774 Dover Cliffs
E16288933.101910 South Foreland
E17405685.961970 Saint Margaret's Bay
E18R = 366??pre-1895
E19410795.191905
E20268833.231910
E21Larger than 1905 chalk flow?1870

Note: L = length; H = height. The above figures (particularly for L), apart from those for E2 and E8, which are based on accurate survey, and E7, for which there was an approximate survey, are largely approximate estimates from newspapers and local scientific societies.

A great fall of uncertain date, approximately below the highest point of Beachy Head, was referred to by Chambers (1862): remnants of this may still exist. In the wet autumn of 1960, a large fall east of the Head is reported to have spread far out across the foreshore (Gilbert, 1964). From about Head Ledge, 1 km east of the lighthouse, to the north-northeast, Albian strata, including the Gault Clay, rise into the cliff foot and the predominant type of failure changes accordingly to deep-seated landsliding.

Although the available records for Sussex are generally imprecise, it seems that the failure of Monkey's Cliff in 1848, west of Beachy Head, was a significant chalk flow and that the failure of 1960, east of the head, may have been considerably smaller. The artificially caused collapse of Seaford Head in 1850, although of large volume, exhibited only a moderate runout. The falls of 1813 and possibly 1853 in the vicinity of Beachy Head and those of 1914 and 1925 from the Seven Sisters were large, but there is no evidence to justify their being classified as chalk flows.

A notable chalk fall at Larklands Point, in November 1933, was reported by Matthews (1934). It is stated that this involved ~150 × 103 t of chalk (i.e., ~79 × 103 m3 of in situ chalk) and that the debris extended “100 yards” (91 m) seaward of the shoreline. Unfortunately, exhaustive enquiries have failed to locate Larklands Point.

Since submission of this paper, a chalk fall occurred at, and immediately west of, the Beachy Head Lighthouse (Fig. 4) on 11 January 1999 (Anonymous, 1999). It extended at least 180 m along the coast, taking a slice generally less that 10 m wide. The run-out was low, my Abney Level readings indicating an 1/h value of ~1.45. This failure thus provides further evidence for the low propensity for chalk flows in these cliffs.

Kent

The main chalk cliffs of Kent are situated where the northern limb of the Wealden anticline, the North Downs, is truncated by marine erosion in a section between the dip and strike directions and on the east and north sides of the chalk outlier forming the Isle of Thanet, in the northeastern part of the county (m). Dips are generally very gentle toward the north or northeast. The cliffs associated with the North Downs extend for ~30 km along the coast and approach a maximum elevation of ~170 m above mean sea level at their southwestern extremity, immediately east of Folkestone. Those of the Isle of Thanet are ~22 km long and reach a maximum elevation of ~30 m at East Cliff, Ramsgate. A summary of the incidence of major chalk falls and flows in Kent is given in Figure 8.

Figure 8.

Incidence of major chalk falls and flows on coast of Kent.

Figure 8.

Incidence of major chalk falls and flows on coast of Kent.

Cliffs associated with the North Downs

The scarp of the North Downs meets the coastline ~1 km east of Folkestone. At this point, ~140 m of Cenomanian and Turonian chalk is underlain by ~45 m of Gault (Albian) (Hutchinson, 1969; Mortimore, 1987). The latter argillaceous stratum provides the seat of failure for the deep-seated Folkestone Warren landslides (Hutchinson, 1969; Hutchinson et al., 1980), which extend eastward for ~3 km.

Folkestone Warren.

Numerous chalk falls (summarized by Hutchinson, 1965) have been reported in the precipitous rear scarp of these landslides, called the High Cliff, since 1765 (Osman, 1917) or possibly 1716 (Hutchinson et al., 1980). Of these, the following are relevant here, having various degrees of flow:

  • A chalk fall of ~52 × 103 m3 (100 × 103 t) of in situ chalk took place from the High Cliff near the west end of the Warren on February 25, 1940 (Ellson, 1940) (Figs. 19 and 20 in Toms, 1946). This appears to have had some element of flow.

  • A similar chalk fall took place from the High Cliff just west of Steady Hole in 1961. The geomorphological map of Hutchinson et al. (1980) indicates that this also had some element of flow.

  • A very large chalk fall took place from the High Cliff at Steady Hole at ~6:30–6:35 p.m. on December 19, 1915 (Anonymous, 1915a, 1915b; Hutchinson et al., 1980). It took ~8 × 103 m2 (2 acres) of land at the cliff top; the debris came to rest landward of the railway line. The geomorphological map of Hutchinson et al. indicates an L/H value of ~1.75 (possibly to ~2.2 in minor lobes).

  • A chalk fall of ~46 × 103 m3 of chalk (it is unclear whether this volume refers to the in situ chalk or to the debris) took place from the High Cliff between Capel Lodge and Abbotscliff House on January 17, 1877 (Anonymous, 1877; McDakin, 1900; Marshall, 1936). It filled the railway cutting for a length of ~140 m, killing two men, and ran out over the beach. It was almost certainly a chalk flow (E3, Table 3; Fig. 8).

  • A chalk fall that blocked the railway to a depth of 18 m took place from the High Cliff near Capel Lodge in September 1885 (Osman, 1917).

  • A very large chalk fall and flow (of smaller volume than the Steady Hole fall but with a much greater runout), known as the “Great Fall” (E2), took place from a nearby part of the High Cliff (elevation 140 m), at ~6.40 p.m. on December 19, 1915 (Anonymous, 1915a). The volume of debris involved was between ~1050 × 103 and 1250 × 103 m3. It blocked the railway cutting, buried Abbot's Cliff signal box, and ran ~550 m beyond the foot of the High Cliff (rear scarp) and 370 m seaward of the high water mark of ordinary spring tides (Fig. 9). A surveyed section of this failure is reproduced in m. A contemporary survey of it in plan is reproduced in Hutchinson et al. (1980, their Fig. 4). The L/H value was 4.19 (Table 3).
    Figure 9.

    View of Great Fall of December 1915 at Folkestone Warren, Kent (acknowledgments to Geological Survey and Museum, now the British Geological Survey).

    Figure 9.

    View of Great Fall of December 1915 at Folkestone Warren, Kent (acknowledgments to Geological Survey and Museum, now the British Geological Survey).

    Figure 10.

    Section of Great Fall of 1915 at Folkestone Warren, Kent (after Osman, 1917). O.D. = ordnance datum ~ mean sea level; WM = water mark.

    Figure 10.

    Section of Great Fall of 1915 at Folkestone Warren, Kent (after Osman, 1917). O.D. = ordnance datum ~ mean sea level; WM = water mark.

Abbot's Cliff.

At the east end of Folkestone Warren, the railway enters a tunnel behind Abbot's Cliff. This cliff is nearly 2 km long and rises to a maximum height of ~140 in. The Gault is now sufficiently far below sea level for the occurrence of deep slips seated in this stratum to be inhibited: it may, however, have permitted slight seaward movements that might have weakened the overlying chalk, consisting of the upper parts of the Cenomanian and the Turanian. Abbot's Cliff is the source of numerous chalk flows; available details are given as follows:

  • The earliest record is that of Smeaton (1769), who examined a very large fall from Abbot's Cliff that took place a little before February 1769, the debris of which covered 6 or 8 acres (~24 × 103 to 32 × 103 m2). It was acting as a natural groyne, which he judged would take a considerable time to wash away. This was clearly a chalk flow (E6).

  • A controlled blast was made at Abbot's Cliff on March 2, 1843 (Anonymous, 1843b). Roughly 38 × 103 m3 of debris was involved; its reach (R), was ~61 m, and the L/H ratio was ~1.72. Two other, smaller controlled blasts were made there in April and May 1843 (Birch and Warren, 1996).

  • A large chalk fall and flow (E4) took place just east of the Folkestone end of the Abbot's Cliff tunnel in 1910. It is reported to have destroyed the sea wall and to have run well out to sea (Wood, 1946).

  • In the same vicinity, a very large chalk fall and flow (E5) took place on December 31, 1911, at 6:30 p.m., i.e., at about the time of high tide. The mass of cliff that fell had been cracked and had sunk by ~0.9 m for some time. The debris extended 366 m out to sea, the width was 183 m and it was as thick as 9 m (Figs. 11 and 12) (Anonymous, 1912a; McDakin, 1912). Its weight was estimated as ~500 × 10−3 t (Anonymous, 1912c). The L/H value is estimated to have been ~3.60. Chalk falls in this part of Kent were observed to have been far more frequent in the last ten years as far east as Saint Margaret's; this was attributed principally to the building of the Dover Harbour extension (Anonymous, 1912b). A similar point was made by Minikin (1952).
    Figure 11.

    View from cliff top of chalk flow of December 31, 1911, at Abbot's Cliff, Kent (acknowledgments to Folkestone Public Library).

    Figure 11.

    View from cliff top of chalk flow of December 31, 1911, at Abbot's Cliff, Kent (acknowledgments to Folkestone Public Library).

    Figure 12.

    View from beach of debris of chalk flow of December 31, 1911, at Abbot's Cliff, Kent (acknowledgments to Folkestone Public Library).

    Figure 12.

    View from beach of debris of chalk flow of December 31, 1911, at Abbot's Cliff, Kent (acknowledgments to Folkestone Public Library).

  • A further substantial chalk fall and flow (E7) in this same general area took place in the night of January 25–26, 1988 (Anonymous, 1988; Birch and Warren, 1996), before 8:00 a.m. on January 26 (A.S. Gale, 1988, personal commun.). This carried away the upper part of one of the Abbot's Cliff Tunnel brick airshafts. A survey by British Rail, Southern Region, in January 1959, showed that a displacement of ~2 m had already occurred on the eventual 1988 slip surface. The cliff there has an elevation of 141 m above sea level. The debris ran out to ~330 m seaward of the cliff foot and had a volume of ~280 × 103 m3. The L/H value was ~3.05. Figure 13 shows the scar of the 1988 failure and its partly eroded debris lobe. A section of this failure is given in Figure 14.
    Figure 13.

    General view of coastline between Folkestone Warren and Dover, Kent, showing partly eroded remains of chalk flow of January 25–26, 1988, with Channel Tunnel platform and Dover Harbour in distance and South Foreland in far distance, taken October 1, 1988 (acknowledgments to Q. A. Photos Ltd., Hythe).

    Figure 13.

    General view of coastline between Folkestone Warren and Dover, Kent, showing partly eroded remains of chalk flow of January 25–26, 1988, with Channel Tunnel platform and Dover Harbour in distance and South Foreland in far distance, taken October 1, 1988 (acknowledgments to Q. A. Photos Ltd., Hythe).

    Figure 14.

    Section of chalk flow of January 25–26, 1988, at Abbot's Cliff, Kent (partly after Birch and Warren, 1996). γd = dry density.

    Figure 14.

    Section of chalk flow of January 25–26, 1988, at Abbot's Cliff, Kent (partly after Birch and Warren, 1996). γd = dry density.

  • Falls in the eastern part of this length of cliff were reported by McDakin (1894, 1900), who noted a very heavy fall of chalk on about November 4, 1892, below Lydden Coastguard Station and a great fall in 1896 at Lydden Spout. No details of runout were given. An aerial photograph of a fall in this vicinity in about 1967 is shown in Figure 15. The fall exhibits some degree of flow. A further substantial fall near Lydden Spout in February 1988, with a reach of 150 m, was reported by Birch and Warren (1996).
    Figure 15.

    View of chalk flow of ca. 1967 near Lydden Spout, Kent (acknowledgments to Skyfotos Ltd, Hythe).

    Figure 15.

    View of chalk flow of ca. 1967 near Lydden Spout, Kent (acknowledgments to Skyfotos Ltd, Hythe).

Figure 13 also provides a good general aerial view of Abbot's Cliff and the cliffs to the east, with the Channel Tunnel platform and Dover Harbour. The partially eroded remains of earlier chalk flows to the east are marked by spreads of flints and blocks of resistant blocks of Melbourn Rock (from the base of the Turonian). Note that the cliffs are generally inclined at ~60°–65° and are commonly oversteepened in their lower parts.

Cliff between Abbot's Cliff and Shakespeare Tunnels.

The 1.3 km length of cliff, up to ~125 m high, between the east portal of the Abbot's Cliff Tunnel and the west portal of the Shakespeare Tunnel, has Cenomanian chalk in its lower part and Turonian in its upper part. It has a maximum elevation of ~125 m. The cliff has been protected at its foot by the railway since 1844. As a result, it appears subsequently to have been slightly less prone to instability than the eroding cliffs to either side of it. Birch (1990) and Hutchinson (1991) studied this length in detail. Several failures with considerable elements of flow have occurred there. A moderately sized failure that took place between the east portal of Abbot's Cliff Tunnel and the west end of the Shakespeare Colliery platform on November 28, 1939, was described by Lee (1940). It crossed the railway lines and entered the sea. The debris volume and L/H ratio for this chalk flow are estimated to have been ~26 × 103 m3 and 1.37, respectively (Hutchinson, 1991).

At the eastern end of this length of cliffs was the artificial failure of January 26, 1843, caused by the blasting of Round Down. This measure was chosen as a cheaper alternative to tunneling for the construction of this part of the railway. The charges, totaling 8390 kg of finest sporting gunpowder, were placed in three short tunnels just above the planned rail level and fired at 2:26 p.m. (Anonymous, 1843a; “S.S.,” 1843). A coastwise length of ~150 m of cliff was involved, so the active charge was ~56 kg/m. The fall of the cliff was described as gradual, being accomplished in two minutes. It appears to have broken down less than a natural chalk fall, especially in its rearward parts (Fig. 16).

Figure 16.

Destruction by blasting of Round Down. Kent (after “S.S.,” 1843).

Figure 16.

Destruction by blasting of Round Down. Kent (after “S.S.,” 1843).

Approximately 300 × 103 m3 of in situ chalk was removed. The average height of the cliff above mean sea level was ~119 m. The shape of the debris lobe was not surveyed below high-tide level. It is reported as covering an area of 63 × 103 m2 to depths varying from 4.6 to 7.6 m and to have had a seaward reach of 305 (Anonymous, 1843b) to 366 m (Anonymous, 1843a) (Fig. 14). The operation was described by Hutchinson (1843). The L/H ratio is estimated to have been ~3.85. The debris from this fall (E8) provided the platform from which the Shakespeare Colliery shafts were sunk from 1896 onward. A further smaller volume of cliff (~50 × 103 m3) was blasted down at 4:30 p.m. on March 2, 1843 (Anonymous, 1843b). Earlier heavy falls affecting Round Down in February 1840 (Anonymous, 1840a, 1840b; Roberts, 1840), and in 1840–1842 were also reported by Hutchinson (1843). The area is now occupied by the spoil from the Channel Tunnel and associated surface structures (seen in the middle distance of Fig. 13).

Shakespeare Cliff.

Shakespeare Cliff, penetrated by the Shakespeare tunnel, extends eastward from the east end of the above platform for nearly 1300 m. It is formed of Cenomanian chalk in its lower part, and Turanian chalk above, and reaches a maximum elevation of ~93 m. This cliff has been the scene of numerous chalk flows. Because their exact locations are usually not known, they are described chronologically:

  • Perry (1721) referred to a notable chalk flow (E14) that occurred “some years since” (probably between ca. 1690 and 1710), some distance westward of the town of Dover. The debris of this shot across the beach down to at least low water mark and stopped entirely the eastward littoral drift. As a result, the mouth of Dover Harbour was freed of gravel, severe erosion developed between the chalk flow and the eastern wall of the harbor basin, so that concern was felt for the safety of the basin. Accordingly, it was decided to blow up the natural groyne formed by the chalk flow, thus restoring the beaches east of the harbor, as well as the harbor bar.

  • Smeaton (1769) also observed a large fall west of Dover, probably from Shakespeare Cliff, that occurred prior to ca. 1767. Because its debris formed a natural groyne, it is probable that this was a chalk flow (E13).

  • Falls probably large enough to generate chalk flows, although there is no firm information on runout, occurred here in 1772 (E9) (Dodsley and Dodsley, 1772) and in about 1810 (Lyell, 1875, v. 1, p. 531–534).

  • A fall in about May 1834, was described as stupendous, the debris still being visible on the shore two years later (Anonymous, 1836); this was doubtless a chalk flow (E12).

  • The debris of a fall in about February 1840 is stated to have covered 2 acres (~8000 m2) (Roberts, 1840): this suggests a moderate chalk flow.

  • Five notable falls took place in February and March 1897. The first, on about February 20, was described as immense (Anonymous, 1897). This was followed, on March 6, by three falls described as enormous (Anonymous, 1897; McDakin, 1899) while, on about March 9, another fall (E11) occurred, said to have been bigger than all the previous 1897 falls together (Anonymous, 1897). No data on runouts were given, but chalk flow behavior seems likely to have been involved.

  • Considerable falls in January 1899 and on March 30, 1909, the latter toward the west end of the cliff, were reported by McDakin (1900 and 1910, respectively). The debris of the 1909 flow extended for 76 m to seaward and was 91 m wide.

  • On about January 1, 1912, a huge fall of “some hundreds of thousands of tons” of chalk took place in the western part of Shakespeare Cliff. The debris is stated to have been some 183 m wide, 9 m deep, and to have extended like a causeway some 366 m out to sea (Matthews, 1918) (E10). Both Matthews (1918) and Minikin (1952) appear to have confused this failure with that of December 31, 1911, at Abbot's Cliff.

  • A big cliff fall took place just east of the western portal of Shakespeare Tunnel in the early morning of Saturday, February 6, 1937. It had an element of flow, projecting seaward ~91 m (Anonymous, 1937a, 1937b).

  • A substantial fall from Shakespeare Cliff in February 1988 was reported by Birch and Warren (1996); no information was provided on runout.

Dover West Cliffs.

The ~2 km of Dover West Cliffs lie between the east portal of Shakespeare Tunnel and the Dour Valley; the cliffs rise to an elevation of ~100 m above sea level and consist of Cenomanian chalk overlain by Turanian chalk. From there, a number of cases of damaging falls into built-up areas have been noted. On January 20, 1853 (McDakin, 1900; Anonymous, 1937c), 100 × 103 t of chalk is estimated to have fallen near Holy Trinity Church, burying Grant's Distillery. In 1894 there was a considerable chalk fall below the prison (Wheeler, 1902) and on February 28 and March 3, 1937, two falls of ~5000 and 17 × 103 t destroyed the Southern Railway Packet Yard (Anonymous, 1937c). In none of these cases is there any firm evidence for a chalk flow, but the failure of 1853 may have generated one.

Dover East Cliffs.

Dover East Cliffs may be taken as extending for ~2 km from the Dour Valley to Langdon Bay. They rise to a maximum elevation of ~100 m on the east side of Langdon Bay. From the valley at Dover to just beyond the castle, these cliffs are formed entirely of Turanian chalk. Farther east, the eastward component of dip brings the Coniacian chalk into the cliff top. In the eastern part of this length, below the castle, a fall occurred on April 6, 1580, at 6:00 p.m., coinciding with an earthquake of intensity 8 in London and taking part of the castle wall (Davison, 1924). There is nothing to suggest that this was a flow slide. Observations made in 1774 in the Dover area (Gilpin, 1804) include the illustration reproduced as Figure 17. This shows, in the cliff directly below Dover Castle and in those immediately to the east and west, the remains of low-angled debris lobes that appear to have been formed by chalk flows (E15), probably between ca. 1760 and 1774. On December 14, 1810, a chalk fall near the gas works demolished a house and killed seven people (“K.B.,” 1828). In November 1872, a large fall of chalk from East Cliff, Dover, destroyed two houses (McDakin, 1900). No information was given on the runout for either of these two cases. In the afternoon of March 5, 1853, “several thousand tons” of chalk fell beyond Atholl Terrace. The considerable mass of debris extended from the base of the cliff to beyond low water mark. No one was hurt, but one man was blown over by the compression of the air (Anonymous, 1853).

Figure 17.

View of Dover Cliff and Castle from Langdon Bay, Kent (after Gilpin, 1804) (by permission of the British Library Reproductions).

Figure 17.

View of Dover Cliff and Castle from Langdon Bay, Kent (after Gilpin, 1804) (by permission of the British Library Reproductions).

Langdon Bay to South Foreland.

Farther east, through Langdon Bay to South Foreland, Turanian chalk forms the base of the cliffs, and Coniacian chalk is above. At South Foreland the latter forms the upper two-thirds of the cliff. On February 23, 1891, at 5:00 p.m., a big fall took place 275 m east of Corn Hill Coastguard Station above Crab Bay (McDakin, 1894). Another very heavy fall occurred in 1896 ~540 m west of South Foreland Low Light in 107-m-high cliffs. It extended ~200 m along the cliff (McDakin, 1897; Wheeler, 1902). Further chalk falls took place on January 28, 1911, between Corn Hill and Fan Bay (McDakin, 1911) and near the South Foreland lighthouse on January 14, 1979 (Anonymous, 1979). No information on runout was given for any of these cases. A heavy chalk fall took place ~1.2 km northeast of the Coastguard Station, at about the South Foreland, the evening of November 11, 1910. This formed a chalk flow (E16) that projected ~230 m out to sea as a natural breakwater (Anonymous, 1910). Its L/H value was ~3.3. An oblique aerial photograph of a considerable fall just below the South Foreland Lighthouse in cliffs of ~85 m elevation is shown in Figure 18. It occurred in about 1961 and exhibited a degree of flow.

Figure 18.

View of chalk fall of ca. 1961 at South Foreland, Kent, with some degree of flow, taken June 29, 1961 (acknowledgments to Aerofilms Ltd).

Figure 18.

View of chalk fall of ca. 1961 at South Foreland, Kent, with some degree of flow, taken June 29, 1961 (acknowledgments to Aerofilms Ltd).

South Foreland to Kingsdown.

The remaining length of eroding chalk cliffs associated with the North Downs extends for ~4.5 km from South Foreland to the south end of Kingsdown, and has a maximum elevation of ~85 m at South Foreland. Stratigraphically, at their southwestern end, these cliffs are formed of Turanian chalk in their lower part, and Coniacian above. The Turanian dips below sea level just northeast of Saint Margaret's Bay, beyond which the cliffs are composed entirely of Coniacian chalk. At Saint Margaret's Bay a tremendous chalk fall, very probably a chalk flow (E18), was reported to have occurred not long before 1895 (Anonymous, 1895). Its exact location is not specified. On the southwest side of Saint Margaret's Bay, a chalk flow (E17) took place on April 5, 1970, at about 11:15 a.m. (Anonymous, 1970a). This is reported to have run out ~275 m into the sea and to have been the heaviest fall in living memory (Anonymous, 1970b). It was unusual in that “the complete face went over like a chimney stack falling.” This cliffs are now ~60 m in elevation.

On the northeast side of this bay roughly 130 × 103 m3 of in situ chalk was involved in a chalk flow (E19) at 9:30 to 10:00 a.m. on January 10, 1905 (Anonymous, 1905a, 1905b, 1905c, 1905d). The debris is reported to have been 6.1–9.1 m thick and to have extended ~370 m out to sea. The L/H ratio for this chalk flow has been estimated as ~5.19. A larger chalk flow (E21) than this was reported to have occurred in the same neighborhood in 1870 (Anonymous, 1905b). A further chalk flow (E20) on the northeast side of Saint Margaret's Bay at Leathercoat Point (where the Dover Patrol Memorial stands, 2.4 km north-northeast of South Foreland) occurred in the evening of November 11, 1910 (Anonymous, 1910; McDakin, 1911). It is reported to have produced a mass of debris 61 m wide that extended as much as ~230 m out to sea to form a natural groyne. Another, less mobile chalk flow took place between Saint Margaret's Bay and Leathercoat Point in the morning of November 17, 1933, at high tide (Anonymous, 1933). The debris had a reach of ~140 m and a height of ~5 m. The only damage was to the last groyne northeast of Saint Margaret's. A fall estimated at 250 × 103 t near St Margaret's Bay took place on February 11, 1947 (Anonymous, 1947). It was attributed to the combined effects of German shelling during World War II and the very cold weather. No information was given on the behavior of the debris. The eroded remains of numerous old chalk flows in this area are indicated on aerial photographs and on the larger scale Ordnance Survey maps.

From an elevation of ~76 m on the north side of Saint Margaret's Bay, the cliffs decline to the north-northeast to an elevation of ~30 m just south of Kingsdown. A fall in 1959, taking a 45-m-long, 18-m-thick slice of the cliff top, is reported between Saint Margaret's Bay and Hope Point (H. Bowdler, County Surveyor of Kent, 1962, personal commun.). He also reported a smaller fall in the same vicinity in March 1962. In neither case is the runout given: they seem unlikely to have been chalk flows. In 1976, I observed a fall north of Hope Point in cliffs of ~40 m elevation, with a negligible element of flow.

Cliffs north of Kingsdown and on the south side of the Thames Estuary.

From ~1.7 km south of Kingsdown, for ~3 km to the north, the chalk cliffs are abandoned, being shielded from marine erosion by a broad gravel beach protected by sea walls.

Low abandoned cliffs of chalk, much quarried, are present in the area of Cliffe, north of Rochester. Their maximum elevation is ~15 m.

Cliffs of the Isle of Thanet outlier

The chalk cliffs of the Isle of Thanet extend for ~22 km from Cliffsend to Minnis Bay. They are generally subvertical and attain a maximum elevation of ~30 m at East Cliff, Ramsgate. They consist of Coniacian chalk in the Ramsgate area and of Santonian chalk to the north, around Margate (Mortimore, 1987; Rowe, 1900). No chalk flows are known from these cliffs, but chalk falls are fairly common.

A typical Thanet chalk fall is that at Joss Bay, in Santonian chalk (Hutchinson, 1972). A cross section is given in Figure 19. The failure was shallow, comprising tension failure, largely on preexisting joints, in the upper half of the cliff and a steeply inclined shear failure through the remaining lower cliff. Failure was facilitated by the formation of a wave-cut notch in the cliff toe. The debris formed a talus inclined at ~35°. The L/H ratio was ~0.64. A photograph of the similar fall of March 5, 1947 at Ramsgate is given in Figure 20.

Figure 19.

Section of chalk fall at Joss Bay, Kent (after Hutchinson, 1972). MHWS = mean high water springs. MLWS = mean low water springs.

Figure 19.

Section of chalk fall at Joss Bay, Kent (after Hutchinson, 1972). MHWS = mean high water springs. MLWS = mean low water springs.

Figure 20.

View of chalk fall of March 5, 1947, at West Cliff, Ramsgate, Kent (after Longworth, 1970).

Figure 20.

View of chalk fall of March 5, 1947, at West Cliff, Ramsgate, Kent (after Longworth, 1970).

Summary of most mobile chalk flows in Sussex and Kent

Table 3 gives approximate details of the 21 most mobile chalk flows identified on the coasts of Sussex and Kent, numbered E1-E21 with L/H ratios, where known, that are between 3.0 and 6.0. The locations of these and less mobile chalk flows are also indicated in Figures 4 and 8.

INCIDENCE IN FRANCE

The chalk cliffs of the northwest coast of France, forming part of the Anglo-Paris Basin, are extensive, reaching from about the mouth of the Seine to Sangatte (Figs. 1 and 3). Their continuity is broken between Cap Gris-Nez and Nesies, south of Boulogne, by the Weald-Artois anticline (Fig. 3) (Bonte et al., 1971, 1985); to the south of this, as far as Ault, the chalk cliffs are abandoned behind the Holocene accumulations, associated with the estuaries of the Canche, the Authie, and the Somme, of “la Plaine Maritime Picarde” (Briquet, 1930; Mennessier et al., 1981; Broquet et al., 1984). The major length of eroding chalk cliffs is farther south, between Ault and the Seine estuary in the Départment of Seine Maritime (Fig. 21, AC). There is a minor length to the north of the anticline, around Cap Blanc Nez in the Départment of Pas de Calais (inset, Fig. 21C).

Figure 21 (on this and following page).

A–C: Incidence of major chalk falls and flows on coast of France between Sainte Adresse and Ault, and around Cap Blanc-Nez. A = Cap de la Hève to Etretat; B = Yport to Pourville-s-Mer; C = Dieppe to Ault. See Figure 2 for L and H definitions, and Table 4 for details of most mobile chalk flows, F1–F9.

Figure 21 (on this and following page).

A–C: Incidence of major chalk falls and flows on coast of France between Sainte Adresse and Ault, and around Cap Blanc-Nez. A = Cap de la Hève to Etretat; B = Yport to Pourville-s-Mer; C = Dieppe to Ault. See Figure 2 for L and H definitions, and Table 4 for details of most mobile chalk flows, F1–F9.

Southern length of eroding chalk cliffs

The morphology of the major southern length of eroding chalk cliffs, which extend for ~130 km (smoothed) between Sainte-Adresse and Ault and rise to a maximum elevation of ~115 m above mean sea level (Fig. 21, AC), was well described by Prêcheur (1960); however, he paid little attention to cliff failures. Descriptions of these cliffs of the Pays de Caux were given by Evrard and Sinelle (1981), who provided useful cliff elevations and profiles but little information on runout, and by Bureau de Recherches Géologiques et Minières (BRGM) (1986), which provided vertical and oblique aerial photographs at a scale of ~1:5000, taken at low tide. The present review is based chiefly on these two publications, together with the 1:50000 geological and 1:25 000 topographical maps, supplemented by a brief reconnaissance I made in 1981. The observations refer to different times between 1981 and 1986 and to features in different stages of marine erosion. Limited historical data are also given.

The trace in plan of the southern length of eroding chalk cliffs is shown in Figure 21 (A–C); the locations of the various chalk flows and their mobility, as explained in the key, are also indicated. Following Evrard and Sinelle (1981), an indication is also given in Figure 21 as to whether the cliffs are formed entirely of chalk (neglecting the capping of Clay-with-flints and overlying Quaternary silts), whether they have clays in the cliff foot, or whether they have a capping of clays. The length of abandoned chalk cliff, immediately northeast of Ault, is also indicated. Where the eroding cliffs are formed entirely of chalk, they are generally subvertical. Where there are clayey strata in the lower cliff, this is naturally less steep, commonly between ~35° and 55°. Similarly, where clayey strata cap the cliffs, that segment of the profile commonly slopes at ~25°. Details of these profiles were given by Prêcheur (1960) and by Evrard and Sinelle (1981).

Cap de la Hève to Saint Jouin-Bruneval.

I am not aware of any chalk flows from the abandoned chalk cliffs of both banks of the Seine estuary or from the deep-seated landslides of Sainte-Adresse (Fig. 21A) at Cap de la Hève, apparently seated principally in the Kimmeridge Clay in the cliff foot (Buisson, 1952). The associated Jurassic strata continue in the cliff foot from Cap de la Hève for at least 9 km northward. The overlying Albian strata occupy the middle and lower middle cliffs to just north of Saint Jouin-Bruneval. Within these is the Gault Clay, which also provides a favorable seat of sliding (Boltenhagen et al., 1968). As a result, considerable failures (éboulements importants) occur from time to time in this length of cliffs, which commonly involve the steep upper cliffs of Cenomanian chalk with flints.

Lennier (1885), quoting Frissard, noted a number of such failures at or near la Hève, e.g., on January 11, 1830. Other examples include the failure that took place in April 1967, 2–3 km north of Cap de la Hève (Boltenhagen et al., 1968), and the fall ~6 km northward that occurred on September 3, 1842, at about 1:00 p.m. (Lesueur, 1842), which involved a 2000 m length of cliff. Two very large landslides in the cliffs of Cap de la Hève on September 7, 1905, at about 7:50 and 8:30 a.m., were reported by Libert (1906). They were estimated to have had a combined volume of 600 × 103 m3 of rock and soil. The debris formed a long promontory, extending out to sea; several fishermen were killed.

The debris of these failures, in at least some cases, traveled sufficiently far seaward to interrupt the gravelly littoral drift. However, because both clays and chalk were involved, and there is insufficient detail to assess the degree to which each contributed to the runout, these events are not accepted here as true chalk flows.

Saint Jouin-Bruneval to Fécamp.

In the 7 km of cliffs from Saint Jouin, northward through Cap d'Antifer to 1.5 km southwest of Etretat, the Albian, the Cenomanian, and eventually the lower Turanian beds pass below sea level; the cliffs from Etretat to the northeast as far as Fécamp are composed of upper Turonian and Senonian chalk, with its generally ubiquitous capping of Clay-with-flints and Quaternary silt (Boltenhagen et al., 1968). Evrard and Sinelle (1981) recorded 2 fresh and 4 old chalk fall scars in the length of cliffs between Bruneval and Etretat and 29 old ones between Etretat and Fécamp.

In summary, for the length of cliffs between Saint Jouin and Fécamp, the present review identifies the 20 chalk flows shown in Figure 21 (A and B). These comprise 6 chalk flows of low runout (L/H 1.37–1.82) on the Le Havre side of Etretat and 14 between Etretat and Fécamp. Of the 14, 11 have low runout (L/H 1.64–2.44), 2 have moderate runout (L/H values of 2.73 and 3.03), and 1 (F1. Table 4; Fig. 21B) has high runout (L/H value of 4.49). The chalk flow debris of moderate runout immediately west of Yport appears on the 1:50000 maps with the name “la Pucelle,” suggesting that it has been resistant to marine erosion.

Table 4.

Most Mobile Chalk Flows Between Saint Jouin-Bruneval and Ault, Northwest France

Chalk flow numberApproximate (Fig. 2)Approximate L/HLocation
L (m)H (m)
F1350784.49Yport(E)
F2320664.85Saint Valery (E)
F3315714.44Saint Valery (E)
F4140344.12Saint Aubin (W)
F5165404.13Saint Aubin (E)
F6400994.04Saint Martin Plage (W)
F7350993.54Saint Martin Plage (W)
F84501024.41Penly
F9345983.52Le Tréport (W)
Chalk flow numberApproximate (Fig. 2)Approximate L/HLocation
L (m)H (m)
F1350784.49Yport(E)
F2320664.85Saint Valery (E)
F3315714.44Saint Valery (E)
F4140344.12Saint Aubin (W)
F5165404.13Saint Aubin (E)
F6400994.04Saint Martin Plage (W)
F7350993.54Saint Martin Plage (W)
F84501024.41Penly
F9345983.52Le Tréport (W)

Note: L = length: H = height. Because the above values are scaled from uncorrected vertical aerial photographs in Bureau de Recherches Géologiques et Minières (1986), they are generally to some degree approximate. An exception to this is case F8, which is based on scaling from the debris lobe shown on the 1:50 000 geological map for Dieppe-Est (Bignot, et al., 1978). Further data could be obtained from the 1:25 000 topographical maps and other vertical air photos.

Fécamp to Saint Valery-en-Caux.

From Cap Fagnet, Fécamp, northeastward to Saint Valery-en-Caux, the cliffs are formed entirely of lower Senonian chalk with the usual capping, except for the first 6 km from Cap Fagnet, where the Turanian chalk forms the base of the cliffs (Ternet, 1969) (Fig. 22). In this overall length, Evrard and Senille (1981) recorded 53 old chalk fall scars and 5 fresh ones. Among the former, the two largest and most interesting are on each side of the Val de la Mer. In both cases, the debris of these falls have largely resisted marine erosion and formed features permanent enough to be mapped and named on the 1:50 000 maps. There is a tendency for beach gravels to accumulate on their northwest sides. The feature to the southwest is named “Le Chien Intrépide”; the larger one to the northeast, understood to have formed in 1944, is “Le Chien Neuf” (Fig. 23). The debris of the latter was mapped (Ternet, 1969) in 1968 as extending above high-tide level ~195 m seaward of the main cliff edge (or ~215 m from the loess-capped cliff top). The value of H at this point is ~104 m. The 1986 BRGM aerial photographs, taken at about low tide, indicate a truer L value for the Chien Neuf debris to be ~320 m, giving an L/H value of ~3.08.

Figure 22.

View of cliffs east-northeast of Cap Fagnet (in background). France, taken September 1981 (my photo).

Figure 22.

View of cliffs east-northeast of Cap Fagnet (in background). France, taken September 1981 (my photo).

Figure 23.

View of Le Chien Neuf, taken September 1981 (my photo).

Figure 23.

View of Le Chien Neuf, taken September 1981 (my photo).

The persistence of these features seems to be due to the blocky nature of the chalk debris involved. It may be significant that both of them are in the length of cliff where the cliff base is formed of Turonian chalk. The curious terminology may spring from the notion that these features look like dogs crouching at the cliff foot. The name “Le Chien Neuf” suggests that there was an earlier, similar feature in the same vicinity. Evrard and Sinei le (1981) also reported several considerable recent chalk falls at Saint Valery-en-Caux, near the Saint Léger tunnel, just west of the town (Fig. 21B). For one of these (Fig. 24), which probably took place in 1980, the debris is stated to have been 120 m wide and 15–20 m thick, with a volume of ~125 × 103 m3. A firm L value is not given: it seems to have been at least 100 m, possibly 150 m. The H value for the cliff is estimated from the 1:25 000 topographical map to be ~67 m, giving an L/H value of as much as ~2.25.

Figure 24.

View of chalk flow of ca. 1980 near Saint Valery-en-Caux (after Evrard and Sinelle, 1981).

Figure 24.

View of chalk flow of ca. 1980 near Saint Valery-en-Caux (after Evrard and Sinelle, 1981).

In summary, in this length of cliffs between Fécamp and Saint Valery-en-Caux, current reconnaissance identifies the 27 chalk flows shown in Figure 21B. Of these, 17 have low runout (L/H from 1.34 to 2.47) and 10 have moderate runout (L/H 2.60–3.29) (Fig. 21B). No chalk flows of high runout were found in this length.

Saint Valery-en-Caux to Dieppe.

From Saint-Valery-en-Caux eastward to Dieppe, the cliffs are formed predominantly of lower Senonian chalk. There are minor cappings of Tertiary sands and clays at Sotteville-sur-Mer and immediately west of Dieppe, and a major capping of these strata, occupying 45%–55% of the cliff, around Varengeville-sur-Mer (Bignot, 1971). Evrard and Sinelle (1981) mapped ~39 old scars, presumably mainly of chalk falls, and 11 fresh ones in this overall length. Around Varengeville, the situation is complicated by the descent of Tertiary slide masses from the upper cliff. The aerial photographs (Bureau de Recherches Géologiques et Minières [BRGM], 1986) indicate faintly a large tongue of chalk debris immediately east of Saint Valery-en-Caux (F2). Its Wd and L values (Fig. 2) scaled from the ~1:5000 air photographs are ~130 m and 320 m, respectively. The topographic map indicates the value of H at this point to be ~66 m, giving a possible rough L/H value as high as 4.85. Evrard and Sinelle (1987) also mentioned “éboulements” in this vicinity in about 1987. The aerial photographs also indicate a further similar feature (F3) in the 300–400 m of cliff just to the east and two smaller features between there and Veules-les-Roses. They also indicate faintly debris tongues ~1100 m west and 900 m east of Saint Aubin-sur-Mer (F4, F5) and two or three substantial slides (presumably from the Tertiary beds) extending across the beach just west of Pourville and smaller ones between there and Dieppe.

In 1875, a few days before February 27, a chalk fall took place in Dieppe from the cliffs ~500 m west-southwest of the casino (Anonymous, 1875). The published sketch, based on a photograph, shows the debris to have formed a talus inclined at ~26°, with no tendency to flow. About 300 m farther west-southwest, a considerably larger failure, measuring 80–90 m along the coast, took place on December 7, 1896, destroying the villa “Bellevue” (Anonymous, 1896; Meunier, 1897). The debris volume was estimated to be ~60 × 103 m3. The cliff there is capped by thick Tertiary sands, and the debris was a mixture of sand and chalk. The chalk, instead of piling up at the foot of the cliff as usual, ran ~200 m into the sea, forming a natural groyne ~8–10 m high. The combined chalk-sand flow is estimated to have had an H/L value of ~3.5.

The present review identifies 10 chalk flows between Saint Valery-en-Caux and Dieppe, as shown in Figure 21 (B and C). Of these, three have low runout (with L/H between ~1.31 and 1.68), 3 have moderate runout (L/H ~2.69–3.37), and four (F2–F5) have high runout (L/H from ~4.38 to 4.85).

Dieppe to Ault.

At each end of the length of coastline between Dieppe and Criel-Plage, the cliffs are formed predominantly of lower Senonian chalk, but in their central parts a gentle flexure brings up the Turonian chalk, which around Saint Martin-Plage forms the lower 80%–85% of the cliff (Bignot et al., 1978). Evrard and Sinelle (1981) recorded 36–38 old and 9 fresh chalk fall scars in this length and described a fall at Penly in cliffs ~98 m high, in which the debris extends possibly 75–90 m into the sea and exhibits an impact hollow (discussed later). A further 250 m to the northeast, a geological map (Bignot et al., 1978) shows a well-marked debris lobe (F8) below the cliffs, which extends far to seaward, with R and L values of ~400 and 450 m, respectively. The cliffs there are ~102 m high, and the L/H value is ~4.41. The BRGM (1986) aerial photographs indicate a remarkable series of 4–6 large debris lobes below the 1–1.5 km of cliffs between Val du Prêtre and Saint Martin-Plage. These are generally ~96 m high; the L values for the sometimes indistinct lobes, scaled from the vertical photographs are, from west to east, ~390, 380, 330, 290, 290, and (from a slightly lower cliff of ~80 m) 230 m. These values yield L/H ratios ranging from 3.33 to 4.04. The two most mobile are F6 and F7. A further large lobe can be distinguished below the northeast end of the cliffs between Saint Martin-le-Plage and Fond de Penly (1.4 km to the northeast). Its L value scales at ~295 m; taking H as ~98 m gives an L/H value of 3.01. These air photographs show a series of three smaller debris lobes below the 1 km length of cliff immediately southwest of Criel Plage. In summary, 26 chalk flows are identified between Dieppe and Criel Plage (Fig. 21C). Of these, 12 have low runout (L/H 1.45–2.28), 11 have moderate runout (L/H 2.51–3.33), and 3 (F6–F8) are have high runout (L/H ~3.54–4.41).

From Criel-Plage to Le Tréport, the cliffs are formed predominantly of Senonian chalk, although for the first 1.5–2 km northeast of Criel-Plage, the Turonian chalk occupies the cliff fool (Evrard and Sinelle, 1981). In this overall length, Evrard and Sinelle (1981) recorded eight old chalk fall scars and no fresh ones. The 1986 aerial photographs indicate a large lobe of debris (F9) below the western Le Tréport cliff (Fig. 25), where H is ~98 m. Scaled values for Wd and L are 190 and 345 m, respectively. The ratio L/H is thus ~3.52. In addition, in this short length, I identified two chalk flows of moderate runout (Fig. 23: L/H values of 2.51 and 3.06).

Figure 25.

View of remains of pre-1986 chalk flow in cliffs west of Le Tréport (Bureau de Recherches Géologiques et Minières, 1986).

Figure 25.

View of remains of pre-1986 chalk flow in cliffs west of Le Tréport (Bureau de Recherches Géologiques et Minières, 1986).

The cliff elevations and mapping of chalk fall scars by Evrard and Sinelle (1981) stop at Le Tréport. The aerial photographic reconnaissance of BRGM (1986) stops at Mers-les-Bains, 2–3 km to the northeast. In the cliffs between Le Tréport and Ault, I identified only one chalk flow, of low runout (L/H = 1.5) (Fig. 19C). Briquet (1930) reported an “éboulement” in 1928 of volume estimated at 100 × 103 m3 in the cliffs north of Mers-les-Bains and a second, ~15 × 103 m3, in the beginning of 1929. In neither of these cases was any information given on runout, but the debris of both falls may have exhibited chalk flow behavior. Northeast of Ault, the chalk cliffs are abandoned by the sea.

Summary of most mobile chalk flows in southern chalk cliffs

The available details of the nine most mobile chalk flows identified in the southern length of eroding chalk cliffs are in Figure 21 (F1–F9) and summarized in Table 4. Their L/H ratios are between 3.5 and 5.0.

All these most mobile flows occur on cliffs composed entirely of chalk. A rough indication of the stratigraphy involved, assuming that each chalk flow is generated by a collapse of the whole height of the cliff, is given in Figure 26. This indicates that the lower parts of the Senonian chalk, specifically the Conacian and the Santonian (broadly the White Chalk with flints), are common to all nine of the cases identified. It is interesting that, as shown by Evrard and Sinelle (1981), these strata include the bed (craie grossière blanche) of lowest average dry density (14.71–15.30 kN/m3) in the Cenomanian, Turanian, and Senonian chalk of northwest France.

Figure 26.

Stratigraphy involved in French chalk flows between Saint Adresse and Ault (* = generally after Evrard and Sinelle, 1981). γdmin = minimum dry density. γd = dry density.

Figure 26.

Stratigraphy involved in French chalk flows between Saint Adresse and Ault (* = generally after Evrard and Sinelle, 1981). γdmin = minimum dry density. γd = dry density.

Northern length of eroding chalk cliffs

North of the Weald-Artois anticline, the minor northern length of eroding chalk cliffs extends for ~6 km from just northeast of Wissant to the interglacial abandoned cliff by Sangatte. The hinterland here, in contrast to the high plateaus of the Pays de Caux and Picardy, consists of a considerably dissected outcrop of chalk, with dry valleys falling to the south, the north, and northwestward to the Channel coast. The cliffs are thus of more moderate heights and of restricted lengths. They rise to ~54 and 101 m above mean sea level at le Petit Blanc-Nez and Cap Blanc-Nez, respectively. In their southwestern part, from southeast of Strouanne to about le Petit Blanc-Nez, the cliffs consist chiefly of marly Cenomanian chalk; upper Albian strata, including the Gault Clay, are in the cliff foot. From there northeast to just beyond le Cran d'Escalles, the cliffs are entirely of the marly Cenomanian chalk. From the latter point northeast to the abandoned interglacial cliff near Sangatte, these Cenomanian beds decline gently toward sea level, the middle and upper cliffs being formed generally of lower and middle Turonian chalk. At two points, Cap Blanc-Nez and the almost equally high bluff 600 m to the northeast, the cliffs are capped by upper Turonian and Senonian chalk (Bonte et al., 1971 ; Robaszynski and Amedro, 1986).

These cliffs are within the area covered by Briquet (1930), but he gave no information on cliff failures there and, apart from the note of a fall at Cap Blanc-Nez on March 30, 1909 (McDakin, 1910), I have found no records of significant chalk flows. The cliffs of le Petit Blanc-Nez are not particularly high and are probably too marly to generate such phenomena. The higher cliffs of Cap Blanc-Nez and immediately to the northeast are also formed predominantly of marly and sometimes nodular Cenomanian to middle Turonian chalk (hence being less steep than the Pays de Caux-Picardy cliffs) and are only thinly capped by the higher porosity, upper Turonian and Senonian White Chalk with flints, which are linked (Fig. 26) with the more mobile chalk flows in the southern cliffs. A general view of the cliffs from le Petit Blanc-Nez to beyond Cap Blanc-Nez is shown in Figure 27. This indicates that the debris of even the three fairly large chalk falls visible on Cap Blanc-Nez (as well as of the various small falls) has come to rest in a normal talus, inclined at ~30°, with no tendency to flow. A photograph of a considerable chalk fall in this same vicinity was shown by Ricour et al. (1987); the debris forms a talus inclined at 32°. Significant chalk flows appear to be absent from this northern length of eroding cliffs.

Figure 27.

View of Cap Blanc-Nez (acknowledgments to Artaud Freres, Carquefou-Nantes).

Figure 27.

View of Cap Blanc-Nez (acknowledgments to Artaud Freres, Carquefou-Nantes).

INCIDENCE IN DENMARK

In Denmark, significant chalky cliffs are found at Stevns Klint, on the southeast coast of Sjaelland, and at Møns Klint, on the east coast of the Island of Møn to the south.

Stevns Klint

The cliffs at Stevns Klint are 12 km long and up to 41 m high. Their lower part is Upper Maastrichtian chalk, which is overlain by massive lower Danian limestone, capped by till. At Sigerslev quarry, 10 km from Stevns Klint, Frykman (1994) reported porosities of 42%–50% in the Upper Maastrichtian chalk. At Stevns Klint, this softer chalk (Skrivekridt) erodes back under marine attack, producing overhangs of several meters in the Danian limestone. As a result, considerable rockfalls occur from time to time. A notable one was that of March 16, 1928, which took the chancel of the old Højerup church (Andersen, 1944; Håkansson, 1971; Rasmussen, 1979b; Surlyk, 1984). These rockfalls do not develop into chalk flows.

About 3 km farther north on Stevns Klint, between Storedal and Eskesti, the strata are raised in a gentle anticline. As a result, the Danian and part of the Upper Maastrichtian have been removed by erosion, so that the entire cliff, ~30 m high, consists of Maastrichtian chalk (Håkansson, 1971). This is probably too low for significant chalk flows to be generated, but the possibility should not be ruled out. A similar situation occurs a little farther north, near Kulsti Rende, but the cliffs there are even lower.

Møns Klint

At Møns Klint, the chalky cliffs are ~8 km long and rise to 128 m above sea level (Fig. 28). They consist of steeply inclined masses of chalk (“floes”) alternating with subparallel beds of glacial material, with the local name of “fald.” All were transported westward from the bed of the Baltic and emplaced by glacial tectonics (Johnstrup, 1874; Slater, 1927; Gripp, 1947). Failures involving variously the glacial clays, sands, and gravels occurred in 1899 at Saettepilefald (Hintze, 1937, p. 65, 67), (now named Saekkepibe Fald), in early 1928 at Hundevaengsfald (Hintze, 1937, p. 239), at Hylledals Fald on July 5, 1980, almost burying two men (Anonymous, 1980a), again on July 8 at the same place, nearly burying a mother and her two children (Anonymous, 1980b), and on July 29, 1994, at Maglevandsfald, when a tourist was killed (Foged, 1994; Schack Pedersen, 1994). These failures, though clearly important, are not relevant here.

Figure 28.

General view of eastern cliffs of Møns Klint, Denmark (acknowledgments to Nordisk Pressefoto, København).

Figure 28.

General view of eastern cliffs of Møns Klint, Denmark (acknowledgments to Nordisk Pressefoto, København).

The Møns Klint Chalk is generally of Lower Maastrichtian age (Rasmussen, 1979b; Surlyk, 1971, 1984). Few porosity measurements in this appear to have been made. Those determined on chalk in connection with the failure at Maglevandsfald in 1994 (Foged, 1994) range from 40% to 44%. Chalk falls are fairly common. The larger failures commonly develop into chalk flows. Information on the principal known failures in the chalk cliffs of Møns Klint is summarized chronologically here and shown in Figure 29.

(1) 1800–1810. A large fall of great extent (“en stor Nedstyrtning … af storre Udstraekning”) occurred at Taleren, a cliff ~100 m high (Hintze, 1937, p. 110–111).

(2) December 24, 1868. A large, catastrophic fall occurred, probably at ~4:00 p.m., at Dronningestolen, the highest (~125 m) and most extensive of the Møns Klint cliffs. It was triggered by atmospheric weathering, particularly frost action, not marine erosion. The cliff involved was wedge shaped, 15 m thick at the cliff top, reducing in thickness downward. The resulting debris was estimated to have had a volume of ~100 × 103 m3, to have been to 10 m thick, and to have covered an area of 1.5 ha (Anonymous, 1868, 1869; Hintze, 1937, p. 99, 339–340). A small island of this debris remained in the sea for several years afterward (“A.F.,” 1913).

(3) 1910. A significant fall occurred at the northern end of Nordre Hundevaengsklint, a cliff ~65 m high. The debris extended some distance out to sea (Hintze, 1937, p. 245, 248, 250).

(4) January 1914. A large fall of chalk and probably some glacial material occurred at Forchhammers Pynt, a cliff ~110 m high. The debris traveled well out to sea (Hintze, 1937, p. 338, 344–345).

(5) January 25, 1939. A large fall occurred at Puggaards Klint, a cliff as much as 94 m high; the debris traveled several hundred meters out to sea (Fig. 30).

Figure 30.

View of chalk flow of January 1939, at Puggaards Klint, Møns Klint; Vitmunds Nakke is in foreground (acknowledgments to Politikens Portraet-Samling).

Figure 30.

View of chalk flow of January 1939, at Puggaards Klint, Møns Klint; Vitmunds Nakke is in foreground (acknowledgments to Politikens Portraet-Samling).

(6) January 1948. A significant fall took place at Dronningestolen (Christensen and Andersen, n.d.) at about the same place as the very large fall 80 yr previously.

(7) January 1952. A large fall, with an estimated weight of several hundred thousand tons, occurred somewhat north of Dronningestolen (exact position uncertain), in cliffs ~125 m high. It “was so powerful that it formed a peninsula, which extended 500 m out from the coast” (Rasmussen, 1979b, p. 131, Fig. 109) (Figs. 31 and 32). The L/H ratio for this chalk flow was ~580/136 = 4.26. The debris was completely removed by the sea in five years.

Figure 31.

Sketch (from air photo) of chalk flow of January 1952, at Dronningestolen, Møns Klint (after Rasmussen, 1979b).

Figure 31.

Sketch (from air photo) of chalk flow of January 1952, at Dronningestolen, Møns Klint (after Rasmussen, 1979b).

Figure 32.

View of chalk flow of January 1952, at Dronningestolen, Møns Klint (acknowledgments to Nordisk Pressefoto, København).

Figure 32.

View of chalk flow of January 1952, at Dronningestolen, Møns Klint (acknowledgments to Nordisk Pressefoto, København).

(8) 1958 (or just previous). A large, fresh fall, with its debris projecting well out to sea, is shown in the vicinity of Vitmundsnakke on an oblique aerial photograph (Redaktionens Arkiv, Berlinske Tidende).

(9) Winter 1962–1963. A large fall took place (locality undefined) (S. Floris, Geological Survey of Denmark, 1980, personal commun.). A photograph of this fall was displayed in 1980 in the museum at the Møns Klint Hotel, showing the debris forming an eroded peninsula out to sea.

(10) 1970. A slide (“skred”) of unspecified type occurred at Store Steilebjerg. (This and the slide at Vidskud are noted in manuscript on my copy of Hintze (1937), presumably by the previous owner, Sigurd Hansen of Valby.)

(11) 1970. A slide of unspecified type occurred at Vidskud.

(12) Before April 23, 1980. A large fall took place just north of Sommarspiret in cliffs probably between 90 and 100 m in height, the debris forming a peninsula out to sea (Politikens Pressefoto).

(13) Night of January 14, 1988. The chalk needle known as Sommarspiret fell. It had existed since at least 1806, and probably earlier.

Figure 29.

Incidence of major chalk falls and flows on east coast of Møns Klint. Key: 1, possible mobile chalk flow (cf); 2, mobile cf; 3, mobile cf, with reach known; 4, possible moderate cf; 5, moderate cf; 6, moderate chalk fall; 7, fall of glacial material (broken lines indicate uncertain location).

Figure 29.

Incidence of major chalk falls and flows on east coast of Møns Klint. Key: 1, possible mobile chalk flow (cf); 2, mobile cf; 3, mobile cf, with reach known; 4, possible moderate cf; 5, moderate cf; 6, moderate chalk fall; 7, fall of glacial material (broken lines indicate uncertain location).

Of these chalk falls, numbers 2, 7, and 8 developed into chalk flows of large runout, as did probably numbers 1, 4, 5, 9, and 12. A more moderate degree of flow sliding seems to have occurred in numbers 3 and 6. Number 13 appears not to have involved a chalk flow. There are no details for numbers 10 and 11.

INCIDENCE IN GERMANY

The most notable chalky cliffs on the coastal cliffs of Germany are those on the Baltic, on the east side of the Island of Rügen, Pomerania, in Jasmund, and, to a lesser extent, Wittow.

Jasmund

The chalky cliffs of Jasmund extend for ~8 km and rise to a maximum height of nearly 120 m. Their average inclination ranges generally between ~50° and 75°. They are closely related, in their glaciotectonic mode of formation and in their lithology, stratigraphy, and geomorphology, to the cliffs described at Møns Klint, having been transported and emplaced by the same westward-moving ice sheet (Gripp, 1947). Glacial materials again separate the highly disturbed masses or floes (Schollen) of Lower Maastrichtian chalk (Weisse Schreibkreide) (Steinich, 1972; Surlyk, 1984; Herrig, 1995). A general view is shown in Figure 33.

Figure 33.

General view in July 1996, of cliffs to south of Kollicker Ort on east coast of Rügen, Germany (my photo).

Figure 33.

General view in July 1996, of cliffs to south of Kollicker Ort on east coast of Rügen, Germany (my photo).

Measurements of the porosity of the chalk have been made at three localities, shown as S 1, 2, and 3 in Figure 34. For S 1 and 2, the values, outside hardgrounds, range from ~42% to 49% and from 40% to 48%, respectively (F.C. Jacobsen, Danmarks og Grønlands Geologiske Undersøgelse [GEUS], 1996, personal commun.), over depths of 3.5 m. At S3, immediately south of the cavity of the 1958 failure, I took a block sample 1 m above the top of beach level that gave dry densities ranging from 14.24 to 14.66 kN/m3. Equivalent porosities, taking the specific gravity of calcium carbonate as 2.71, are 46.4% and 44.8%, respectively. A porosity of 46% has been determined by Böttcher (1985) for the chalk at the nearby quarry of the VEB Kreidewerke at Klementelvitz, Rügen. The information on notable failures on the predominantly chalky parts of the Rügen cliffs, from an admittedly incomplete literature search, is summarized below and shown in Figure 34. On this figure, the numbers in brackets after the landslide dates refer to the list below. Failures (3) and (11) are not shown since their locations have not been found:

(1) A failure (Abbruch) occurred in January 1905, just north of the Lenzer Bach (Scholle 4) (Jaekel, 1917).

(2) An enormous failure (reisige Abbruch) occurred in 1912 in the Arndt-Warte (Scholle 9), caused by the quarrying of blocks for the building of the harbor at Sassnitz. The mass involved is reported as having extended 90 m along the coast and encroached landward by 30 m from the cliff edge (Jaekel, 1917).

(3) A very large failure (Bergsturz) took place on February 14–15, 1914, resulting from erosion of the cliff base by the storm surge of 1913–1914 (Keilhack, 1914). The volume of debris is given as 250 × 103 m3, but this was doubted by Hurtig (1961). The location is not specified.

(4) A failure (Abbruch), not much smaller than that of 1912, occurred in 1915 in the cliffs of the Rabenklinke (Scholle 6) (Jaekel, 1917; see also background of sketch, Fig. 13 of Jaekel, 1930).

(5) A large failure is inferred to have taken place just south of the Ernst-Moritz-Arndt-Sicht in about 1915. Its debris, with toe eroded away, was sketched in August 1916 by Jaekel (1930, his Fig. 21).

(6) A similar failure took place in 1916 about halfway between Kieler Bach and Kollicker Bach (Scholle 16) (Jaekel, 1917).

(7) A fall (Absturz) of chalky material took place just north of Wissower Bach in 1916 (Jaekel, 1930, his Fig. 13).

(8) A failure (Abbruch) involving chiefly chalky material took place in 1917 just south of Hengst (Jaekel, 1930, his Fig. 10).

(9) A small failure (Nachrutsch) is reported to have occurred in 1920 at the crest of the Ernst-Moritz-Arndt-Sicht, affecting only Pleistocene material (Hurtig, 1964, quoting Jaekel).

(10) At noon on May 19, 1936, a young geologist, Volkmar Wroost, was killed by a failure many hundred of cubic meters in volume while making observations at the foot of a 40 m high cliff in the Arndt-Schlucht, near Wissower Klinken (Richter, 1936). The debris was described as mud (Schlamm), suggesting that Pleistocene materials were involved rather than chalk. It appears not to have been a chalk flow.

(11) A large failure (Bergrutsch) took place in the spring of 1955 in the same vicinity as the 1914 failure (Hurtig, 1961).

(12) On May 21–22, 1958, a large chalk fall occurred in two parts from the ~45–60 m high cliffs north of Wissower Klinken. The larger, first collapse (12-I) (grosse Kreideausbruch) took place ~100 m south of Ernst-Moritz-Arndt-Sicht and was estimated to involve roughly 70 × 103 m3 of predominantly solid chalk (perhaps more, to judge from the debris volume). This transformed into a chalk flow (Kreidestrom) with a debris volume of ~126 × 103 m3 that extended ~200 m along the coast, ran 130–150 m out to sea from the cliff foot, and had a maximum thickness of ~12–13 m (Fig. 35). The L/H ratio is estimated to have been ~227/63 = 3.6. A second collapse (12-II), a similar distance on the other (north) side of Ernst-Moritz-Arndt-Sicht, followed closely. It extended ~95 m along the coast and slightly more than 100 m out to sea. Its L/H value was ~2.6. These measurements of the extent of the two debris lobes, which almost merged into one, will tend to underestimate the maximum values as they were taken on June 14, 1958, i.e., about three weeks after the failure. More than half the total volume of debris was washed away by the sea within nine months. Total removal of the debris was expected to take about two and a half years (Hurtig, 1959a, 1959b, 1961, 1964).

Figure 35.

View of ~40% eroded chalk flow of May 1958, at Wissower Klinken, Rügen, Germany (photo by Lebrecht Jeschke, Griefswald).

Figure 35.

View of ~40% eroded chalk flow of May 1958, at Wissower Klinken, Rügen, Germany (photo by Lebrecht Jeschke, Griefswald).

Hurtig (1961) stated that no quarrying or strong toe erosion by the sea were involved in the failures of May 1958; he believed that they were triggered by the heavy rainfall and high groundwater levels of April and particularly May 1958, helped by earlier frost action. He also considered that the structure and interrelationships of the disturbed Cretaceous and Pleistocene strata in this vicinity predispose the cliffs to failure and create a particular weak stretch (Schwachestelle) in them. The distribution of known failures shown in Figure 34 provides some support for this view.

(13). In the early months of 1982, a considerable failure in the chalk cliffs took place immediately north of the Ernst-Moritz-Arndt-Sicht (H. Schnick, Nationalparkamt Rügen; 1996, personal commun.). Contemporary photographs indicate that the debris was very broken and formed a moderate chalk flow with a L/H value estimated very roughly to be ~2.

(14). In the spring of 1994 a large failure (grosser Abbruch) took place halfway between Kieler Bach and Kollicker Bach (H. Nestler, Ernst-Moritz-Arndt-Universität, Greifswald, 1996, personal commun.).

Figure 34.

Incidence of major chalk falls and flows on east coast of Rügen (Jasmund and Cap Arkona). Key: 1, possible mobile chalk flow (cf); 2, mobile cf with reach known; 3, moderate cf with reach known; 4, moderate cf; 5, fall of glacial material.

Figure 34.

Incidence of major chalk falls and flows on east coast of Rügen (Jasmund and Cap Arkona). Key: 1, possible mobile chalk flow (cf); 2, mobile cf with reach known; 3, moderate cf with reach known; 4, moderate cf; 5, fall of glacial material.

Of these failures, number 12-I is the only one certainly of high L/H, but numbers 2 to 6, 11, and 14 may have exhibited a degree of chalk flowing. Failure number 12-II was a chalk flow of moderate L/H, as were probably numbers 8 and 13. Numbers 7, 9, and 10 do not appear to have involved chalk flows. The lack of information precludes the classification of failure number 1.

Wittow

The Weisse Schreibkreide also forms the lower parts of Kap Arkona, in Wittow at the northern extremity of the Isle of Rügen, where Neumayr and Suess (1920) reported a cliff recession of 300–400 m in 100 yr. A landslide took place there in about July 1966, in a cliff ~45 m high, forming a wedge of debris extending ~40 m out to sea (Benek, 1969). This consisted chiefly, however, of Pleistocene material (older and younger tills separated by interglacial sands and clays) from the upper half of the cliff, and little chalk was involved.

Discussion and Conclusions

Relation between porosity (dry density) of the chalk and its propensity for flow sliding

Early in this study, following Clarke (1977) and Clayton (1990), it emerged that porosity, or the more readily measured dry density, is the most useful index test to use in characterizing the chalk. Clayton (1990) gave the ranges of porosity and dry density in British chalks as 9%–52% and 24.13−12.65 kN/m3, respectively. It was immediately evident that chalk flows are unknown in the harder, denser chalks of, e.g., Northern Ireland and Yorkshire, and are best developed in the softer chalks of southeast Kent.

Largely through data from Clayton (1978a, 1978b, 1983), it was possible to construct the summary plot of porosity (dry density) against stratigraphy for the English chalk, shown in Figure 36. A similar study was made by Bloomfield et al. (1995). With the help of colleagues in Denmark and Germany, this plot has been extended to cover Møns Klint and Rügen. While Figure 36 could clearly be improved by further work, it is believed to give a useful indication of these relationships. Once the hardness classification and known incidence of chalk flows are added, it is seen that these are confined to the softer chalks. An exact boundary between chalk-flow prone and nonprone material is unlikely to exist, because other variables such as cliff height and slide volume will have some influence. However, the plot suggests that, in the areas studied, the transition from chalk flow to nonchalk-flow behavior occurs at a porosity of ~40%, or a dry density of ~15.95 kN/m3, corresponding to very soft chalk. This boundary is concordant with the known occurrences of chalk flows in southeast Kent, Møns Klint, and Rügen, and with the rarity of such failures in Sussex. The absence of chalk flows in the very soft Santonian chalk elsewhere in Kent, around the Thames Estuary, and in the soft Campanian of Norfolk is explained by the absence of sufficiently high cliffs in these localities. Giant quarries for cement production are being contemplated in the former area, so care must be taken to avoid generating artificial chalk flows in these.

Figure 36.

Relationship of chalk flow incidence to distributions of porosity (dry density) and hardness against stratigraphy for various coastal chalk regions of Britain, Denmark, and north Germany. Ur Chk = upper chalk; Mid Chk = middle chalk; Lr Chk = lower chalk.

Figure 36.

Relationship of chalk flow incidence to distributions of porosity (dry density) and hardness against stratigraphy for various coastal chalk regions of Britain, Denmark, and north Germany. Ur Chk = upper chalk; Mid Chk = middle chalk; Lr Chk = lower chalk.

With regard to the coastal chalks on each side of the Channel Tunnel, there is some evidence (Table 5) that these are harder and denser, on average, on the French side. This, with the other factors noted here, may help to explain the apparent absence of chalk flows in the Cap Blanc-Nez cliffs. I have insufficient data to make a useful review of these matters for the extensive southern French cliffs.

Table 5.

Average Dry Densities for Strata on the English and French Sides of the Channel Tunnel

StratumEngland densities (kN/m3)France densities (kN/m3)
Middle Chalk16.3818.44
White Chalk17.0619.61
Grey Chalk—Upper19.0319.81
Grey Chalk—Lower20.1021.18
Chalk Marl—Upper20.3021.28
Chalk Marl—Lower19.1219.91
Glauconitic Marl20.4021.58
Upper Gault17.5518.44
Lower Gault17.3619.61
StratumEngland densities (kN/m3)France densities (kN/m3)
Middle Chalk16.3818.44
White Chalk17.0619.61
Grey Chalk—Upper19.0319.81
Grey Chalk—Lower20.1021.18
Chalk Marl—Upper20.3021.28
Chalk Marl—Lower19.1219.91
Glauconitic Marl20.4021.58
Upper Gault17.5518.44
Lower Gault17.3619.61

Note: Data after Channel Tunnel Study Group (1966), v. III, Section X, p. 10–16.

Some general information on the distribution of types of chalk in the Anglo-Paris Basin was given by Mortimore et al. (1990a). Their summary map for southern England (Fig. 37) accords very well with the incidence of chalk flows there. On the northern French cliffs, however, no chalk flows have been recognized in the area designated, apparently in conflict with Table 5, as being of extremely soft to soft chalk. The nine most mobile chalk flows identified on the French coast (Table 4) are all situated in the very variable Pays de Caux area mapped as “very hard nodular chalks and hardgrounds to extremely soft chalks.” Clearly, more detailed work is needed.

Figure 37.

Distribution of types of chalk in Anglo-Paris Basin (after Mortimore et al., 1990a).

Figure 37.

Distribution of types of chalk in Anglo-Paris Basin (after Mortimore et al., 1990a).

Collapse of metastable structure and generation of high excess pore-water pressures

It has been suggested that the mobility of chalk flows arises from high undrained excess pore-water pressures generated in their basal parts by a process of impact collapse, predominantly as the falling chalk hits the toe platform (Hutchinson, 1980, 1983, 1984, 1988). The usually dry and blocky debris forming the surface of chalk flows is presumed to be carried seawards on this high pore-pressure underlayer. The process is limited to the softer chalks and requires a minimum energy input, or height of fall, implying the existence of a dynamic pore collapse threshold. The mechanism is related to that of undrained loading put forward by Hutchinson and Bhandari (1971) for mudslides and other types of landslide. As indicated by the electrical piezometer measurements in Hutchinson and Bhandari (1971), a distinction may be made between undrained self loading, within the incoming debris, and undrained superimposed loading of the underlying material forming the toe (in this case, shore) platform. It is probable that undrained self-loading usually predominates. The degree to which further excess pore-water pressures will be generated through the undrained superimposed loading of the shore platform by the impact and dead weight of the arriving chalk debris depends on the nature of that platform. If it is jointed hard chalk or a coarse gravel beach, any such pressures are likely to dissipate very rapidly. However, if it is mantled by saturated finegrained colluvium (including putty chalk) from earlier chalk flows, the superimposed undrained loading will tend to give rise to important additional excess pore-water pressures that will increase the runout of the debris. Undrained loading in such situations was explored by Sassa (1992) and Sassa et al. (1992).

No measurements of pore-water pressures in the field have so far been made in chalk flow debris. (An unsuccessful attempt to arrange this, using a helicopter to lift in a drilling rig, was made at the time of the 1988 chalk flow at Abbot's Cliff.) The mechanism of generating excess pore-water pressures through impact collapse of a high- porosity, metastable chalk structure is thus largely inferred at present. The end product of this process is “putty (fully remoulded) chalk” (Hutchinson, 1983, p. 9) and the finding of significant quantities of this, in September 1996, within the debris of old chalk flows below Abbot's Cliff, is compelling evidence for the former existence of excess pore-water pressures in these. As would be expected, the smashed material there exhibits a brecciated fabric consisting of angular fragments of chalk, down to submillimeter sizes, in a matrix of putty chalk (Fig. 38). Eight water-content measurements on such material on the foreshore below the eastern part of Abbot's Cliff ranged from 21.2% to 29.3%; the average was 26.0%. These samples were taken at low tide, between 50 and 108 m seaward from the cliff toe, in the upper 0.5 m of eroded old debris flow material (the first 43 m of the foreshore was covered by a gravel beach) of unknown thickness. It appeared at the site of the more inshore samples (50–56 m from cliff foot) as if the smashed and putty chalk had extruded up into the coarse debris (with blocks to 3 m, occasionally 5 m across) from below (Fig. 38). The more distal sample (108 m from the cliff foot) appeared to be less smashed.

Figure 38.

Brecciated chalk in putty chalk matrix, in chalk flow debris below eastern part of Abbot's Cliff, Kent, September 1996 (my photo). Tape case is 170 mm in diameter.

Figure 38.

Brecciated chalk in putty chalk matrix, in chalk flow debris below eastern part of Abbot's Cliff, Kent, September 1996 (my photo). Tape case is 170 mm in diameter.

Subsequently, further evidence of the association of putty chalk with the debris of former chalk flows was provided by Trenter and Warren (1996), who reported up to 45 m of gravel- to cobble-sized chalk debris in a matrix of soft putty chalk in boreholes on the Folkestone Warren undercliff, below its chalk-flow-prone rear scarp.

Given that saturation is achieved largely through capillarity, the pore-water pressure in the in situ cliff will tend generally to be strongly negative. However, once the chalk fall has begun, with the separation of individual blocks, these negative pore-water pressures will immediately reduce to values appropriate to the sizes and boundary conditions of the blocks. Then, when impact on the shore platform occurs, the impact collapse mechanism is potentially so powerful in the soft, high-porosity chalks that high excess pore-water pressures will readily be generated.

Supporting evidence of some form of collapse of chalk structure under dynamic loading is provided by several civil engineering activities. In the softer chalks, it is well known that putty chalk is produced by pile driving. No associated excess pore-water pressures appear to have been measured, although Hobbs and Healy (1979) stated that it is generally accepted that driving a pile into Type A chalk (soft friable chalk of high porosity, greater than 35%), in which the water content usually exceeds the plastic limit of the remoulded chalk, produces a sleeve of crushed and remoulded chalk under high porewater pressure which considerably reduces the friction on the shaft during driving. There are some cases in which pile-bearing capacity has increased with time after driving, possibly indicating the dissipation of such pore-water pressures, but this is difficult to separate from other effects, such as pile set-up (R. J. Jardine, Imperial College, 1996, personal commun.).

Classification boundaries for chalk, based on intact dry density, were reviewed by Mortimore and Fielding (1990). They and Mortimore et al. (1990b) take “extremely soft” chalk as having a dry density <15.20 kN/m3 and “very soft” chalk as 15.20–15.69 kN/m3. Both categories form putty chalk when struck with a hammer. In a subsequent review of foundations in chalk (Lord et al., 1993), “low density” chalk, which readily remolds to form a putty, is also defined as having an intact dry density of <15.20 kN/m3. The next stronger category of “medium density” chalk, which can be crushed by a hammer blow, has intact dry densities between 15.20 and 16.67 kN/m3. It should be noted that putty chalk can also be formed by nondynamic, natural processes such as frost weathering (Higginbottom and Fookes, 1970; R. Shephard-Thorn, British Geological Survey, 1996, personal commun.).

Intact dry density criteria, similar to those given herein, combined with water content, affect the compaction of chalk fills and the generation of excess pore-water pressures and putty chalk in these. Rat and Schaefner (1990), for example, took a dry density value 14.71 kN/m3 as the boundary in French practice between relatively weak and medium strong chalks in this context, while Clarke (1977), for English and French conditions, identified serious problems in placing earthworks of chalk where the intact dry density is <~15.0 kN/m3 and some problems for values of 15.0–15.3 kN/m3. Not surprisingly, these dry density values are closely similar to those given earlier as the maxima for chalk flow occurrence.

Negative bulking, of as much as 11%–12% (i.e., bulking factors of 0.89−0.88), indicating that collapse is occurring, is reported for well-compacted fills of soft chalk by Parsons (1966) and by Jenner and Burfitt (1974), respectively.

Under static loading, the softer chalks exhibit considerable settlements once a threshold stress is exceeded, again behaving rather like a bonded or lithified sensitive soil (Jones, 1990). The associated mechanism has been termed “pore collapse” (e.g., Botter, 1985; Schroeder, 1995). The large subsidence in the high- porosity North Sea chalks of the Ekofisk Oil Field, following the reduction of fluid pressure there, is a striking example of this (Jones et al., 1990). In the laboratory, undrained triaxial tests with pore-pressure measurement on high-porosity chalk show stress paths characteristic of a collapsible material (Fig. 39). It would be interesting to attempt to relate these static and dynamic pore collapse thresholds.

Figure 39.

Stress path for undrained triaxial compression test with pore-pressure measurement on Butser Hill chalk of porosity of 36.9%–37.3% (M. Leddra, Imperial College, 1988, personal commun.).

Figure 39.

Stress path for undrained triaxial compression test with pore-pressure measurement on Butser Hill chalk of porosity of 36.9%–37.3% (M. Leddra, Imperial College, 1988, personal commun.).

Influence of the state of the tide

Assuming that excess water pressures are inherent in chalk flows, the question arises as to whether the water involved is chalk pore-water or seawater, for failures on the coast, or both of these? The correlation of chalk-flow with high-porosity chalk points strongly toward the chalk pore water. The exact times of failures generating chalk flows are rarely known, so it is usually uncertain whether the chalk debris hits the beach at low tide, or falls directly into the sea at high tide. Cases where the date and time of failure is known are summarized in Figure 40. They show no clear relationship to the state of the tide. Of particular interest in this connection, however, is the Great Fall of 1915 in Folkestone Warren. The debris from this first struck the shelf of former landslipped material forming the Undercliff. It began to flow at that point, crossed the >200-m-wide undercliff, and only then ran out to sea (Figs. 9 and 10). Similar behavior was also exhibited by the chalk fall and flow of 1877 there. These cases indicate that the presence of seawater is not necessary for chalk flowing to be induced. When seawater is present, additional transient pressures may be generated in it: it will also tend to exert a drag on the debris movement.

Figure 40.

Incidence of coastal chalk flows in relation to state of tide.

Figure 40.

Incidence of coastal chalk flows in relation to state of tide.

Steepness and hydrogeology of chalk cliffs as influencing chalk flow incidence

A comparison of the Folkestone-Dover cliffs with those running west from Beachy Head suggests strongly that mobile chalk flows are associated with steep but non-vertical cliffs (~60°–75°) and that vertical cliffs, even if higher, do not generally generate chalk flows. The main underlying reason for this is the porosity of the in situ chalk; where this is high, rendering the chalk flow-slide prone, the cliffs are soft and weather back; where the porosity is low, the rock is hard, joint-dominated, stands vertically, and is not prone to chalk flows. Further factors, involving the failure volumes and degrees of saturation, are outlined in the following.

Data on the variation of water content and degree of saturation within different chalk cliffs is lacking. Some very preliminary speculations on the hydrogeology in two types of such cliffs are illustrated in Figure 41. First, it is assumed, following Hutchinson (1972) and other evidence, that the groundwater table is generally low in chalk cliffs. However, the capillary rise in chalks is known to be high; e.g., such rocks were reported as being saturated to a height of >80 m above the groundwater table by Evrard and Sinelle (1981). This situation is likely to be influenced by the presence of joints and fissures. Evidence for the saturation or near-saturation of chalks well above the phreatic surface, even in quarry faces after a hot summer, was provided by Mortimore and Fielding (1990, their Fig. 3). Figure 41 outlines speculative suggestions for the extent of the zones of saturation in vertical and sloping chalk cliffs.

Figure 41.

Comparison of volumes and hydrogeology involved in failures in nearly vertical cliffs of hard chalk and in less steep cliffs of softer chalk. O.D. = ordnance datum ~ mean sea level, GWT = groundwater level. See Figure 2 for definitions of L and H.

Figure 41.

Comparison of volumes and hydrogeology involved in failures in nearly vertical cliffs of hard chalk and in less steep cliffs of softer chalk. O.D. = ordnance datum ~ mean sea level, GWT = groundwater level. See Figure 2 for definitions of L and H.

For the vertical cliffs, modeled on the joint-dominated cliffs of hard chalk forming the Seven Sisters in Sussex, the runout of the debris from the chalk fall is limited. This is partly because of the restricted volume of debris produced per meter run by failures in such cliffs and partly because much of the falling chalk is probably unsaturated. By contrast, the sloping cliffs of softer chalk yield a much larger volume of debris per meter run (based here accurately on the failure that generated the chalk flow of January 1988, at Abbot's Cliff) which, because the failure is much more deep seated, is largely saturated. In addition, the concave-upward shape of the associated slip surface will tend to give the slide masses a larger initial seaward velocity. For these three reasons, therefore, the runout in the second case is much enhanced.

The association of chalk flows with steep but not vertical cliffs is continued in the cliffs of glacially disturbed chalks at Møns Klint and Rügen. However, the situation on the French coast is more complex and less clear: e.g., chalk flow F8 at Penly (Evrard and Sinelle, 1981, p. 47) is associated with a non-vertical cliff, but other chalk flows appear to derive from nearly vertical cliffs. Further research is needed.

Influence of cliff height on chalk flows

If the chalk is too hard and dense, even the highest vertical cliffs, such as the western parts of Beachy Head, are unable to generate chalk flows. Although it is very rarely possible to find a situation in nature permitting the influence of just one variable to be explored, it is instructive to examine the chalk cliffs of east and southeast Kent, where in general the chalks are soft enough to be flow-slide prone and cliff heights vary between ~20 and 140 m.

The fall at Joss Bay, Isle of Thanet (Hutchinson, 1972), is typical for the northern part of this length of cliffs. The cliff elevation is 20 m; failure is joint controlled in the upper half of the cliff and the lower half fails by shear at a high angle. The debris forms a talus inclined at ~35° at the base of the cliff, with no element of flow (Fig. 19). A similar situation applies 7–8 km farther south at Ramsgate (Fig. 20). Farther south, near Kingsdown, is the start of the cliffs formed by the truncation of the North Downs. A fall with a negligible element of flow took place in cliffs ~40 m high just north of Hope Point. Around Saint Margaret's Bay, a few kilometers southwest, the cliffs are higher and prone to very mobile chalk flows; e.g., that of January 1905 (E19) took place in a cliff of 76 m elevation and had an L/H ratio of 5.19. About 1 km farther southwest, at South Foreland, the cliffs are still higher, with an elevation of ~85 m, but falls there generate less mobile chalk flows than at Saint Margaret's Bay (Fig. 18). This doubtless arises chiefly because of the greater proportion of chalk of high dry density in the cliffs at South Foreland in comparison with those around Saint Margaret's Bay (Fig. 42), which also probably underlies the physiographical contrast between headland and bay. As shown by Figures 42 and 43, the east cliff of Saint Margaret's Bay has both the greatest thickness of the lowest density chalk in Kent and the most mobile chalk flows known in northwest Europe. In the reverse sense, the beach access known as Langdon Stairs, a couple of kilometers farther southwest, is of interest. This was built in the nineteenth century, down an undefended cliff, but has survived to the present day, probably because it is situated almost wholly on chalk of high dry density (Fig. 42).

Figure 42.

Elevation of Kent cliffs between Folkestone and Kingsdown (after Hutchinson, 1991) (γd values supplied by R.N. Mortimore).

Figure 42.

Elevation of Kent cliffs between Folkestone and Kingsdown (after Hutchinson, 1991) (γd values supplied by R.N. Mortimore).

Figure 43.

Plot of L/H against H for more mobile coastal chalk flows of northwest Europe. N = highest cliff fall in Kent without flow sliding (Fig. 12, Hutchinson, 1988). See Figure 2 for definitions of L and H.

Figure 43.

Plot of L/H against H for more mobile coastal chalk flows of northwest Europe. N = highest cliff fall in Kent without flow sliding (Fig. 12, Hutchinson, 1988). See Figure 2 for definitions of L and H.

As indicated by the elevation of Figure 42, the cliffs rise in height from the west side of Dover to the western end of Folkestone Warren and also include a large proportion of chalk of low dry density. Accordingly, this entire length of cliffs is prone to very mobile chalk flows, with a tendency for the most mobile to be associated with the higher cliffs toward the western end of this length (Table 1; Figs. 8 and 42). This is also indicated by the greater thickness of putty chalk in boreholes toward the western end of Folkestone Warren, reported by Trenter and Warren (1996).

A plot of L/H against H for all reasonably well documented chalk flows in northwest Europe is given in Figure 43. Given the uncertainties attaching to some of the data and the unconsidered influences of dry density and debris volume, too much should not be read into this; however, the following points may be made:

  • Unsurprisingly, there is no clear trend of increase in mobility with increase of cliff height. For these limited data, mobilities for cliffs in the 70–80 m H range exceed those for both higher and lower cliffs.

  • The maximum L/H value recorded is nearly 6.0.

  • The French chalk flows form a group of similar or greater mobility than the surveyed Kentish flows, even though their cliff heights are considerably smaller. They are exceeded in mobility only by the two Saint Margaret's Bay flows of 1905 and 1970, which are from cliffs of comparable height to the French ones.

  • The Møns Klint chalk flow of 1952 is closely comparable with the more mobile of the surveyed Kentish examples.

  • The Jasmund chalk flow of 1958 is comparable with the less mobile of the French cases.

The minimum height of chalk cliff from which a chalk flow can be generated will depend on the average dry density of the chalk, its degree of saturation, the nature of its cementation, jointing, and Assuring, the cliff profile, the volume of the failure, and perhaps the rate of toe erosion. It is of some interest, however, to see from Figure 43 that all but the two Saint Aubin cases (F4 and F5) involve cliffs of H >~65 m (i.e., cliffs >~60 m in elevation H′, Fig. 2). By comparison, the fall near Hope Point from the 46 m high cliff mentioned above (N on Fig. 43, taken from Fig. 12 of Hutchinson, 1988) exhibited a negligible degree of flow. The Saint Aubin cases are notable for generating chalk flows (of L/H>4) from cliffs with H of only ~35 m (i.e., of elevation H′ of ~32 m). These cases are thus critical and should be checked.

Bulking factors for chalk flow debris

Information on the degree of bulking from solid chalk to chalk flow debris volume is, at best, approximate. P.M. Varley (Trans Manche-Link, 1991, personal commun.) gave a value of 1.34 for loosely tipped Chalk Marl below Shakespeare Cliff; Church (1981) quoted a value of 1.50 for United States chalks. A value of 1.67 can be derived for the Great Fall of 1915 in Folkestone Warren (Osman, 1917), but this is considered too high because of doubt about the in situ chalk volume. The fall of 1843 at Round Down, brought down by explosives, yielded values of 1.37–1.57.

In chalk falls, the great majority of the debris can be expected to exhibit positive bulking, but that involved in impact collapse will show a negative bulking. Overall, therefore, a high estimate may be 95% bulking at 1.5, plus 5% at 0.9, = a net bulking factor of 1.47; a low estimate may be 95% at 1.35, plus 5% at 0.9, = a net bulking factor of 1.33. Within this range, it is suggested that 1.4 be taken as an average value of bulking factor (Hutchinson, 1991).

Runout, speed, and general morphology of chalk flows

The runout of chalk flows depends on the numerous factors discussed herein, for many of which there is a lack of data. An empirical approach was therefore made to the estimation of runout in connection with the Channel Tunnel headworks (Hutchinson, 1988, 1991; results shown in Fig. 44). Theoretical approaches based inter alia on the methods of Hungr (1995) and Hutchinson (1986) are being pursued.

Figure 44.

Plot of H/L (inverse of mobility) against log of debris volume for chalk flows from Kentish cliffs (Hutchinson, 1988, 1991). See Figure 2 for definitions of L and H.

Figure 44.

Plot of H/L (inverse of mobility) against log of debris volume for chalk flows from Kentish cliffs (Hutchinson, 1988, 1991). See Figure 2 for definitions of L and H.

No observation appears to have been made of the speed of a natural chalk flow. However, in the blasting down of Round Down in 1843, “S.S.” reported that two minutes were required for “its descent and dispersion.” This crude estimate would indicate an average speed of ~470 m in 120 s, i.e., ~4 m/s. Even a maximum speed double this might be on the low side (O. Hungr, University of British Columbia, 1996, personal commun.).

Sparse information on the relation between the reach, R, and average width, forumla, of natural chalk flow debris lobes shows a wide variation, with forumla ranging from ~0.15 to >0.8. The thickness of debris, Td, is usually between ~4 and 11 m, but can be 19 m in more blocky debris, e.g., in Le Chien Neuf. The long axes of debris lobes are generally approximately normal to the line of the coast, but can deviate from this direction by as much as ~10°. As shown by Figures 13, 15, and 25, the coarser debris tends to accumulate around the margins of chalk flow lobes.

In some cases a feature, here termed an impact hollow, is formed in the debris just out from the cliff foot (e.g., Figs. 1315, and Evrard and Sinelle, 1981, fall at Penly, p. 47). Somewhat similar features have been reported from rock debris accumulations in Norway, e.g., at abrupt concave changes in slope (Liestøl, 1974; Corner, 1980). However, Liestøl (1974) and Corner (1980) ascribed the hollow principally to the ejection of debris by water and to the repeated impact of snow avalanches, respectively. Clearly, neither of these mechanisms is valid in the present context, where the hollows are a direct product of the dynamics of the chalk debris. They are probably analogous with the fall-back ridges, with associated depressions on their upslope side, that I observed in the Mayunmarca debris in Peru (Hutchinson and Kojan, 1975). In the light of this new evidence, the origin of the Norwegian features might bear reexamination.

Seasonal nature of chalk flows

The distribution, by month of the year, of the more mobile coastal chalk flows in northwest Europe is shown in Figure 45. Their strongly seasonal nature is evident, the bulk of the failures taking place between November and April, inclusive. More rarely, they can occur in September or October and in May. No cases are known from June, July, or August. The comparable distribution of chalk falls on the Kent coast was shown and possible controlling factors for these were discussed in Hutchinson (1972).

Figure 45.

Incidence of coastal chalk flows by time of year.

Figure 45.

Incidence of coastal chalk flows by time of year.

Hazards posed by chalk flows

Coastal chalk flows, with debris volumes often in excess of 100 × 103 m3 and rapid runouts of as much as five to six times the cliff height, clearly constitute potentially lethal and very damaging natural hazards, although the damage they have caused appears to have been moderate. There is no record of a person on the cliff top being involved in a fall leading to a chalk flow, though the vicar of East Dean had a narrow escape in 1813 at Beachy Head. Sparse data for such events indicate that encroachment on the cliff crest ranges up to 24 m, with b/H′ (Fig. 2) values for the most part being between ~0.1 and 0.2, but rising to 0.3, depending on the joint control. A theoretical expression for b/H′, based on a Joss Bay model, was given in Hutchinson (1972).

The cliff foot is, as would be expected, more dangerous. Two coastguards were nearly buried by a chalk flow just west of Beachy Head in 1848 and two platelayers were killed on the railway in Folkestone Warren by the chalk flow of 1877. The deaths of seven people in a house below Dover East Cliffs in 1810 appear to have been caused by a chalk fall rather than a flow. No information has been found on casualties from true chalk flows in France. However, an unknown number of fishermen were killed by the combined clay and chalk failure at Cap de la Hève in September 1905. At Møns Klint, two people on the beach had a narrow escape on July 5, 1980, and a further three at the same place on July 8. A tourist was killed there in 1984. In May 1936, a geologist was killed at the foot of the Jasmund cliffs. These events in Denmark and Germany appear to have involved failures in predominantly glacial material rather than chalk flows.

This fortunately moderate number of casualties probably results largely from the distribution of chalk flows throughout the year (Fig. 45). They have been limited almost entirely to the winter half of the year when the beaches tend to be fairly deserted. The months of September, October, and May, when the holiday season overlaps with the “tails” of the chalk flow distribution, are the most dangerous.

Material damage to nearshore structures has also been limited, affecting chiefly artificial groyne systems and, to a lesser extent, sea walls. More significant has been the interruption of littoral drift by the debris of chalk flows acting as natural groynes, which has from time to time adversely affected the harbor at Dover. Beachy Head lighthouse, constructed by 1902 on the shore platform 185 m out from the toe of 130-m-high cliffs, has escaped damage, probably because chalk flows at that locality are inhibited by a moderate but crucial decrease in chalk porosity toward the west (Fig. 7). Some of the recently constructed Channel Tunnel headworks, such as the ventilation plant, are sited on a platform of debris and spoil beneath steep, high cliffs of soft chalk west of Shakespeare Cliff, and are thus exposed to a potential future hazard from chalk flows, because significant failures can occur even decades after a chalk cliff has been defended or abandoned. Protective measures were provided to guard against this possibility. No case is known of a boat being overwhelmed by a chalk flow (the la Hève case was not a true chalk flow and it is assumed that the fishermen lost were on shore).

Little is known about the recurrence interval for repeated chalk flows in the same place. On eroding cliffs it is likely to be a function of the local intensity of toe erosion. The best data on this are from France, for the coast from Cap d'Antifer to le Tréport for the period 1830–1966 (Bialek et al., 1969). A distinction is made between the retreat of the cliff crest and cliff foot; for the latter, values range from 0 to 62 m in the 136 yr, i.e., to 0.46 m/yr on average. In Sussex, for the chalk cliffs from Brighton to Beachy Head, Thorburn (1977) gave average erosion rates (not specified as to cliff crest or foot) ranging from 0 to ~1.5 m/yr. The Møns Klint 1948 failure, if truly in about the same place as that of 1868, would indicate a recurrence interval there of 80 yr. Much shorter intervals seem likely for the more exposed and active Kentish cliffs, but precise data are lacking.

Submarine chalk flows?

Can chalk flows of the type described here occur under water? Rifting in the North Sea Basin, continuing into the mid-Cretaceous, created the Central Graben there. Tectonic activity in Maastrichtian and Danian time brought about instability in the form of slumps, slides, debris flows, and turbidites, particularly along the faulted margins of the graben. The material involved was redeposited in the Central Trough as allochthonous chalks which, because of their enhanced porosity (30%–50%), particularly where originating from debris flows, now form the best oil and gas reservoirs (Kennedy, 1985; D'Heur, 1993). The scale and variety of submarine mass movements within the Central Graben are clearly of the utmost importance: however, it is questionable whether chalk flows deriving from an impact-collapse mechanism were involved. Buoyancy and drag resistance may cushion any subaqueous chalk falls sufficiently to inhibit the efficacy of such a mechanism.

Conclusions

1. Chalk flows, hitherto rather neglected, have been established as a significant form of failure on the coastal cliffs of northwest Europe.

2. Chalk flows are particularly prevalent on coastal cliffs in southeast Kent, England, and Møns Klint, Denmark, are common on the coast between Yport and le Tréport, Pays de Caux, France, and occur occasionally on the cliffs of Jasmund, Rügen, Germany.

3. Chalk flows originate as chalk falls; the debris then runs rapidly seaward, for distances of as much as five to six times the cliff height. As noted in Hutchinson (1983), their mobility is similar to that of Alpine Sturzstroms (Hsü, 1975), but is achieved by a quite different mechanism at debris volumes approximately two orders of magnitude smaller. The most mobile case known, at Saint Margaret's Bay, Kent, has an L/H value of 5.96, equivalent to a “fahrböschung” (Heim, 1932) of 9.5° (Fig. 2).

4. Chalk flows occur in chalks of porosity of ~40% or more and in cliffs generally of height H>~65 m (i.e., >~60 m in elevation, H′, m):however, at St. Aubin, France, chalk flows of L/H>4 appear to have been generated in cliffs of height H ~35m.

5. Chalk flows are a type of flow slide; excess pore-water pressures are inferred to be generated primarily in their basal parts by a mechanism of undrained self loading through impact collapse in the falling, high-porosity soft chalk. Additional excess water pressures may be derived from the undrained superimposed loading of the shore platform, at least where this is mantled by fine-grained, saturated colluvium from earlier chalk flows. The presence of seawater at the cliff foot, at high tide, will doubtless have some effect on debris runout, but is not essential for chalk flow formation.

6. The occurrence of chalk flows is strongly seasonal, usually being confined to the months of November–April, inclusive. So far, they appear to be absent in June, July, and August; however, they occur occasionally in September, October, and May.

7. Although chalk flows are potentially lethal and highly damaging, particularly because of their speed, volume, and remarkable mobility, they have so far caused only moderate damage and few fatalities, this last being ascribed to their tendency to take place in the winter, when the coastline is fairly deserted.

Desirable Further Work

1. Pore-water pressures should be measured at various depths within a fresh chalk flow and during pile driving in chalks of various hardnesses.

2. Laboratory tests should be developed to simulate the impact collapse phenomenon and to relate the dynamic and static collapse thresholds.

3. Existing empirical methods of estimating chalk flow runout should be improved and theoretical approaches to this problem should be developed, covering both falls onto dry ground and into the sea.

4. The distribution of water content, degree of saturation, and negative pore-water pressures within various chalk cliffs should be measured.

5. The sedimentology of subaerial chalk flow deposits should be studied and whether submarine ones occur should be further explored.

6. The relationships between cliff morphology, lithology and structure, failure types and run-out, and intact dry density in chalk cliffs, particularly along the coast of northwest France, should be studied further.

References Cited

“A.F.,”
1913
,
Møens Klint
:
Møens Turistforening, Stege
 ,
30
p.
Andersen
,
S.A.
,
1944
,
Det Danske Landskabs Historie: Danmarks Geologie i Almenfattelig Fremstilling (2. Staerkt for0gede udgave). Bind 1, Undergrunden
 :
København
,
Populaer-Videnskabeligt Forlag
,
480
p.
plus Tidstavler 1 a–g
.
Anonymous
,
1813
,
Fall at East Dean: Gentleman's Magazine
:
London, D. Henry and R. Cave
 , v.
83
, p.
278
.
Anonymous
,
1836
,
A walk under the Shakespeare and other poems
 :
London
,
W. Prescott; Dover, B. Steill
.
Anonymous
,
1840a
,
Great fall of cliff at Dover
 :
The Times
,
London
,
6th
February
, p.
5
.
Anonymous
,
1840b
,
Encroachments and recessions of the sea
:
Civil Engineer and Architect's Journal, Scientific and Railway Gazette
 , v.
3
, p.
167
168
.
Anonymous
,
1843a
,
Destruction of the Round-Down-Cliff by gunpowder
 :
The Times
,
London
,
27th
January
, p.
5
.
Anonymous
,
1843b
,
Another great blast at Dover
 :
The Times
,
London
,
3rd
March
, p.
5
.
Anonymous
,
1850
,
Grand explosion at Seaford Cliff
:
Illustrated London News, 21st September
 , v.
17
, p.
242
.
Anonymous
,
1853
,
The Bay of Dover and the cliffs of Dover
 :
The Times
,
London
,
8th
March
, p.
8
.
Anonymous
,
1868
,
Møens Klint
 :
Møens Avis
,
Møen
, post-
25
December
.
Anonymous
,
1869
,
Dronningestolens Nedstortning
 :
Faedrelandet
,
København
, no.
7
.
Anonymous
,
1875
,
L'éboulement de Dieppe
 :
Le Monde Illustré
,
Paris
,
19e année
, no.
933
,
27th
February
, p.
152
.
Anonymous
,
1877
,
The landslip
 :
Folkestone Chronicle
,
Folkestone
,
20th
January
, p.
5
.
Anonymous
,
1895
,
Falling cliffs in Kent
 :
The Standard
,
London
,
8th
June
, p.
4
Anonymous
,
1896
,
La villa Bellevue à Dieppe
 :
Le Monde Illustré
,
Paris
,
40e année
, no.
2072
,
12th
December
, p.
377
.
Anonymous
,
1897
,
Herne Bay Press
,
Herne Bay
,
13th
March
, p.
7
.
Anonymous
,
1905a
,
St. Margaret's Bay, Dover
:
Nature
 , v.
71
, no.
1837
, p.
253
and 279.
Anonymous
,
1905b
,
The landslips near Dover
 :
The Times
,
London
,
16th
January
, p.
7
.
Anonymous
,
1905c
,
The great landslide at Dover: The fallen cliff
:
Illustrated London News, 21st January
 , v.
126
, p.
82
.
Anonymous
,
1905d
,
Fall of cliff at St. Margaret's
 :
The Dover Express and East Kent News
,
Dover
, Friday,
13th
January
,
1905
, p.
5
.
Anonymous
,
1910
,
Fall of cliff
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
18th
November
, p.
10
.
Anonymous
,
1912a
,
Ground disturbed by rain. Fall of cliff between Dover and Folkestone
 :
The Times
,
London
,
2nd
January
, p.
6
.
Anonymous
,
1912b
,
The landslide near Dover
 :
The Times
,
London
,
3rd
January
, p.
4
.
Anonymous
,
1912c
,
Great fall at Abbott's Cliff
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
5th
January
.
Anonymous
,
1914
,
Great fall of cliff at one of the Seven Sisters
 :
Eastbourne Gazette
,
Eastbourne
,
22nd
April
, p.
5
.
Anonymous
,
1915a
,
Great landslide. Line wrecked in Warren
 :
Folkestone Express
,
Folkestone
,
25th
December
, p.
8
.
Anonymous
,
1915b
,
Big landslide in Folkestone Warren
 :
Folkestone, Hythe, Sandgate, and Cheriton Herald
,
Folkestone
,
25th
December
, p.
2
.
Anonymous
,
1933
,
Fall of cliff near Dover. Result of heavy rains
 :
The Times
,
London
,
18th
November
, p.
12
.
Anonymous
,
1937a
,
Thames again rising
 :
The Times
,
London
,
8th
February
, p.
12
.
Anonymous
,
1937b
,
Another cliff fall
 :
The Dover Express and East Kent News
,
Dover
,
12th
February
, p.
5
, 9.
Anonymous
,
1937c
,
Big cliff fall
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
5th
March
, p.
2
, 9.
Anonymous
,
1947
,
White cliffs of Dover
 :
The Evening Standard
,
London
,
12th
February
, p.
1
.
Anonymous
,
1970a
,
Cliff fall turned sea white
 :
East Kent Mercury
,
Deal
,
9th
April
, p.
1
.
Anonymous
,
1970b
,
Big cliff fall follows rain, snow, and frost – and more may follow
 :
The Dover Express and East Kent News
,
Dover
,
10th
April
, p.
3
.
Anonymous
,
1979
,
Heavy cliff fall
 :
The Daily Telegraph
,
London
,
16th
January
, p.
3
.
Anonymous
,
1980a
,
Sprang for livet pa Møns Klint under Kaempeskred
 :
Møns Tidende
,
Stege
,
7th
July
.
Anonymous
,
1980b
,
Tysk familie sekunder fra døden ved nyt klinte-skred
 :
Møns Tidende
,
Stege
,
11th
July
.
Anonymous
,
1986
,
Golf course hit as cliffs crash into sea
 :
Evening Argus
,
Brighton
,
16th
July
, p.
1
.
Anonymous
,
1988
,
Landslip halts trains
 :
Folkestone, Hythe and District Herald
,
Folkestone
,
29th
January
, p.
3
.
Anonymous
,
1999
,
Photo caption
:
Geoscientist
 , v.
9
, no.
2
, February 1999, p.
3
.
Beckett
,
1929
,
Perils of Beachy Head
:
Sussex County Magazine
 , v.
3
, p.
630
633
.
Benek
,
R.
,
1969
,
Rezente Rutschung am Kap Arkona auf Rügen
:
Zeitschrift für angewandte Geologie, Sonderbeilage
 , v.
15
, no.
9
, p. between 472 & 473.
Bialek
,
M.
Grosse
,
M.
Foucaud
,
M.
,
1969
,
Recul des falaises du cap d'Antifer au Tréport (entre 1830 et 1966)
:
Direction Départementale de l'Equipement, Service maritime, Section 2, Arrondissement Maritime de Dieppe
 .
Bignot
,
G.
1971
,
Carte géologique au 1:50000, Dieppe-Ouest (Feuille XIX-8)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bignot
,
G.
Auffret
,
J-P.
Monciardini
,
C.
Moal
,
A.
,
1978
,
Carte géologique au 1:50000, Dieppe-Est (Feuille XX-8)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Birch
,
G.P.
,
1990
,
Engineering geomorphological mapping for cliff stability: Chalk
 :
London
,
Thomas Telford
, p.
545
549
.
Birch
,
G.P.
Warren
,
C.D.
,
1996
,
The cliffs behind the Channel Tunnel workings: Chapter 7
, in
Harris
,
C.S.
Hart
,
M.B.
Varley
,
P.M.
Warren
,
C.D.
, eds.,
Engineering geology of the Channel Tunnel
 :
London
,
Thomas Telford
, p.
76
87
.
Birkelund
,
T.
Hancock
,
J.M.
Hart
,
M.B.
Rawson
,
P.F.
Remane
,
J.
Robaszynski
,
F.
Schmid
,
F.
Surlyk
,
F.
,
1984
,
Cretaceous stage boundaries: Proposals
:
Bulletin of the Geological Survey of Denmark
 , v.
33
, p.
3
20
.
Bishop
,
A.W.
,
1973
,
The stability of tips and spoil heaps
:
Quarterly Journal of Engineering Geology
 , v.
6
, p.
335
376
.
Bjerrum
,
L.
,
1971
,
Subaqueous slope failures in Norwegian fjords
 :
Norwegian Geotechnical Institute
Publication 88
, p.
1
8
.
Bloomfield
,
J.P.
Brewerton
,
L.J.
Allen
,
D.J.
,
1995
,
Regional trends in matrix porosity and dry density of the Chalk of England
:
Quarterly Journal of Engineering Geology
 , v.
28
,
Supplement 2
, p.
S131
S142
.
Boltenhagen
,
C.
Menillet
,
F.
Ternet
,
Y.
,
1968
,
Carte géologique au 1:50000, Montivilliers-Etretat (Feuille XVII-9-10)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bonte
,
A.
Broquet
,
P.
Destombes
,
J.-P.
Somme
,
J.
Hatrival
,
J.-N.
et al
,
1971
,
Carte Géologique au 1:50000, Marquise (Feuille XXI-3)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bonte
,
A.
Broquet
,
P.
Destombes
,
J.-P.
et al
,
1985
,
Carte géologique au 1:50000, Boulogne-sur-Mer (Feuille 2104)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Böttcher
,
H.
,
1985
,
Stoffliche Zusammensetzung und Eigenschaften des Rohstoffes Kreide
:
Zeitschrift für angewandte Geologie
 , Band
31
, Heft
3
, p.
62
67
.
Botter
,
B.J.
,
1985
,
Pore collapse measurements on chalk cores
, in
Second North Sea Chalk Symposium
:
Stavanger, Norway
,
Book 2
, p.
1
12
plus 13 figs.
Bourdillon
,
F.W.
,
1884
,
Beachy Head
:
Transactions of the Eastbourne Natural History Society, New Series
 , v.
1
, p.
4
21
.
Briquet
,
A.
,
1930
,
Le Littoral du Nord de la France et son evolution morphologique
 :
Paris
,
Librairie Armand Colin
,
439
p.
Broquet
,
P.
Beun
,
N.
Dupuis
,
C.
et al
,
1984
,
Carte géologique au 1:50000, St-Valery-sur-Somme-Eu (Feuille 2007–2107)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Buisson
,
M.
,
1952
,
Les glissements de la falaise de Sainte-Adresse
:
Annales de l'Institut Technique du Bâtiment et des Travaux Publics, 50th année
 , no.
59
, Supplement, p.
1130
1145
.
Bureau de Recherches Géologiques et Minières
,
1986
,
Étude du littoral Haut Normand entre Le Havre et Le Tréport: Rapport General
 :
Maisons-Alfort
,
Laboratoire Central d'Hydraulique de France
.
Burgoyne
,
J.F.
,
1851
,
Paper 13. 1. Preliminary observations on the mining operations for blowing down the cliff near Seaford, on the coast of Sussex, in August and September, 1850
:
Professional Papers of Royal Engineers, New Series
 , v.
1
, p.
68
69
.
Casagrande
,
A.
,
1936
,
Characteristics of cohesionless soils affecting the stability of slopes and earth fills
:
Journal of the Boston Society of Civil Engineers
 , v.
23
, p.
13
32
.
Castleden
,
R.
,
1982
,
Landform Guides No. 2: Classic landforms of the Sussex coast
 :
Sheffield
,
The Geographical Association
,
39
p.
Chambers
,
G.F.
,
1862
,
Contributions towards a history of Eastbourne
:
Sussex Archaeological Collections
 , v.
14
, p.
119
137
.
Channel Tunnel Study Group
,
1966
,
Channel Tunnel: Site investigations in the Strait of Dover 1964–1965
:
Courbevoie, France, and London, Channel Tunnel Study Group
 , v.
3
, Section 10, p.
1
36
.
Choubert
,
G.
Faure-Muret
,
A.
,
1976
,
Geological World Atlas
 :
Paris
,
UNESCO
,
scale 1:10000000
.
Christensen
,
P.R.
Andersen
,
H.C.
, eds., n.d. (ca.
1959
),
Gads Små Egnsboger, Møn
:
G.E.C. Gads Forlag
 ,
64
p.
Church
,
H.K.
,
1981
,
Excavation Handbook
 :
New York
,
McGraw Hill Book Company
,
954
p.
Clarke
,
R.H.
,
1977
,
Earthworks in soft chalk: Performance and prediction
:
The Highway Engineer
 ,
March
, p.
18
21
.
Clayton
,
C.R.I.
,
1978a
,
Chalk as fill
 
[Ph.D. thesis]
:
Guildford
,
University of Surrey
,
489
p.
Clayton
,
C.R.I.
,
1978b
,
A note on the effects of density on the results of Standard Penetration Tests in chalk
:
Geotechnique
 , v.
26
, p.
119
122
.
Clayton
,
C.R.I.
,
1983
,
The influence of diagenesis on some index properties of chalk in England
:
Geotechnique
 , v.
33
, p.
225
241
.
Clayton
,
C.R.I.
,
1990
,
The mechanical properties of the Chalk
 :
Chalk, London
,
Thomas Telford
, p.
213
232
.
Corner
,
G.D.
,
1980
,
Avalanche impact landforms in Troms, north Norway
:
Geografiska Annaler
 , v.
62
A, p.
1
10
.
Dassargues
,
A.
Monjoie
,
A.
,
1993
,
Belgium
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
153
169
.
Davison
,
C.
,
1924
,
A history of British earthquakes
 :
Cambridge
,
Cambridge University Press
,
416
p.
D'Heur
,
M.
,
1993
,
The Chalk as a hydrocarbon reservoir
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of Northwest Europe
 :
Oxford
,
Clarendon Press
, p.
251
266
.
Dodsley
,
R.
Dodsley
,
J.
,
1772
,
Annual Register
 :
London
,
R. Dodsley and J. Dodsley
.
Ellson
,
G.
,
1940
,
Contribution to Discussion on Duvivier
:
Journal of the Institution of Civil Engineers
 , v.
14
, p.
428
431
.
Evrard
,
H.
Sinelle
,
C.
,
1981
,
Stabilité des Falaises du Pays de Caux
:
Le Grand-Quevilly, Centre d'Etudes Techniques de l'Equipment
 ,
87
p.
Evrard
,
H.
Sinelle
,
C.
,
1987
,
La stabilité des falaises du Pays de Caux-Normandie: Actes du Colloque Mer et Littoral couple à risque
:
Biarritz
 ,
11–13
Septembre
, p.
84
91
.
Foged
,
N.
,
1994
,
Møns Klint: Evaluering af skred og sikringstiltag foreløbig vurdering
 :
Lyngby, Geoteknisk Institut, Rapport 1, 1994-08-08
,
12
p.
plus 6 figures
.
Frome
,
R.E.
,
1851
,
Paper 13. 2. Mining operations at Seaford
:
Professional Papers of Royal Engineers, New Series
 , v.
1
, p.
69
79
.
Frykman
,
P.
,
1994
,
Variability in petrophysical properties in Upper Maastrichtian chalk outcrops at Stevns, Denmark: A contribution to the EFP-92 Project: Stochastic modelling of petrophysical properties in chalk
 :
Copenhagen
,
Geological Survey of Denmark
,
DGU [Danmarks Geologiske Undersøgelse] Service report
, no.
38
,
10
p.
plus 20 figures
.
Geikie
,
A.
,
1903
,
Text-book of geology
  (4th edition):
London and New York
,
Macmillan and Co Ltd.
,
2
vols.,
1472
p.
Gilbert
,
R.
,
1964
,
Changing face of Beachy Head
 :
Eastbourne Gazette
,
Eastbourne
,
12th
August
, p.
21
.
Gilpin
,
W.
,
1804
,
Observations on the coasts of Hampshire, Sussex, and Kent … made in the summer of the year 1774
 :
London
,
T. Cadell & W. Davies
,
135
p.
Gripp
,
K.
,
1947
,
Jasmund und Möen, eine glacial-morphologische Untersuchung
:
Erdkunde, Band
 
1
, p.
175
187
.
Gustafsson
,
O.
,
1993
,
Sweden
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
208
219
.
Håkansson
,
E.
,
1971
,
Geologi på Øyerne, 1, Sydostsjaelland og Møn–Varv ekskursionfører Nr 2, Stevns Klint
 :
Mineralogisk Museum
,
København
, p.
25
36
.
Hancock
,
J.M.
,
1986
,
Cretaceous
, in
Glennie
,
K.W.
, ed.,
Introduction to the petroleum geology of the North Sea
 :
Oxford
,
Blackwell
, p.
161
178
.
Harris
,
E.
,
1943
,
Submerged and reclaimed coastal Sussex
:
Sussex County Magazine
 , v.
17
, p.
260
262
.
Heim
,
A.
,
1932
,
Bergsturz und menschenleben
:
Beiblatt zur Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich
 , no.
20
,
Jahrgang 77
, p.
1
218
.
Herrig
,
E.
,
1995
,
Die Kreide und das Pleistozän von Jasmund, Insel Rügen (Ostsee)
, in
Katzung
,
G.
Hüneke
,
H.
Obst
,
K.
, eds.,
Geologie des südlichen Ostseeraumes—Umwelt und Untergrund, 147
 .
Haupt-ver-sammlung der Deutschen Geologischen Gesellschaft Exkursionsführer
,
4–6
Oktober
,
Greifswald
, p.
91
113
.
Higginbottom
,
I.E.
Fookes
,
P.G.
,
1970
,
Engineering aspects of periglacial features in Britain
:
Quarterly Journal of Engineering Geology
 , v.
3
, p.
85
117
.
Hintze
,
V.
,
1937
,
Møens Klints Geologi
 :
København
,
C.A. Reitzels Forlag
,
410
p.
Hobbs
,
N.B.
Healy
,
P.R.
,
1979
,
Piling in chalk
 :
London
,
Construction Industry Research and Information Association
,
DoE and CIRIA Piling Development Group, Report PG6
,
126
p.
Howell
,
J.
,
1874
,
On the geology of Brighton
:
Proceedings of the Geologists’ Association
 , v.
3
, p.
168
188
.
Hsü
,
K.J.
,
1975
,
On Sturzstroms: Catastrophic debris streams generated by rockfalls
:
Geological Society of America Bulletin
 , v.
86
, p.
129
140
.
Hungr
,
O.
,
1995
,
A model for the runout analysis of rapid flow slides, debris flows, and avalanches
:
Canadian Geotechnical Journal
 , v.
32
, p.
610
623
.
Hurtig
,
T.
,
1959a
,
Der grosse Kreideausbruch auf Rügen im Jahre 1958
:
Natur und Heimat
 , Jahrgang
8
, Heft
9
, p.
460
463
.
Hurtig
,
T.
,
1959b
,
Über die Uferzerstörungen an der Steilküste von Rügen (NSG Jasmund) im Jahre 1958
:
Naturschutzarbeit und naturkundliche Heimatforschung
 , Heft
2
, p.
2
6
.
Hurtig
,
T.
,
1961
,
Der grosse Bergrutsch 1958 am dem Kreidesteilufer nördlich Sassnitz auf Rügen
:
Geographische Berichte, Mitteilungen der Geographischen Gesellschaft der Deutschen Demokratischen Republik
 , Heft
18
, p.
1
8
.
Hurtig
,
T.
,
1964
,
Eine Naturkatastrophe am Kreidsteilufer von Rügen
:
Natur und Museum
 , Bd.
94
, Heft
9
, p.
331
342
.
Hutchinson
,
G.R.
,
1843
,
Account of the demolition and removal by blasting of a portion of the Round Down Cliff, near Dover, in January, 1843
:
Professional Papers of Royal Engineers, Quarto Series
 , v.
6
, p.
188
203
.
Hutchinson
,
J.N.
,
1965
,
A survey of the coastal landslides of Kent
 :
Watford
,
Building Research Station
,
Note No. EN 11/65
,
117
p.
Hutchinson
,
J.N.
,
1969
,
A reconsideration of the coastal landslides at Folkestone Warren, Kent
:
Geotechnique
 , v.
19
, p.
6
38
.
Hutchinson
,
J.N.
,
1972
,
Field and laboratory studies of a fall in Upper Chalk cliffs at Joss Bay, Isle of Thanet
, in
Stress-strain behaviour of soils, Proceedings of the Roscoe Memorial Symposium, Cambridge
:
Henley-on-Thames, G.T. Foulis & Co. Ltd
, p.
692
706
.
Hutchinson
,
J.N.
,
1980
,
Various forms of cliff instability arising from coastal erosion in the U.K.
:
Fjellsprengningsteknikk-Bergmekanikk-Geoteknikk 1979, 19.1–19.3. Trondheim, Tapir, for Norsk Jord-og-Fjellteknisk Forbund tillknyttet NIF
 
Hutchinson
,
J.N.
,
1983
,
Engineering in a landscape: Inaugural Lecture
 ,
9th
October
,
1979
:
London
,
Imperial College, University of London
,
12
p.
Hutchinson
,
J.N.
,
1984
,
Landslides in Britain and their countermeasures
:
Journal of Japan Landslide Society
 , v.
21-1
, p.
1
24
.
Hutchinson
,
J.N.
,
1986
,
A sliding-consolidation model for flow slides
:
Canadian Geotechnical Journal
 , v.
23
, p.
115
126
.
Hutchinson
,
J.N.
,
1988
,
General report: Morphological and geotechnical parameters of landslides in relation to geology and hydrogeology
, in
Bonnard
,
C.
, ed.,
Landslides, Proceedings, 5th International Symposium on Landslides, Lausanne
:
Rotterdam
/
Brookfield, A.A. Balkema
, p.
3
35
.
Hutchinson
,
J.N.
,
1991
,
Lower Shakespeare Site: Cliff stability and run-out study
:
Report to Engineering and Power Development Consultants Limited
 ,
October
,
33
p.
plus 16 figures (unpublished)
.
Hutchinson
,
J.N.
,
1995
,
Keynote Paper: Landslide hazard assessment
, in
Bell
,
D.H.
, ed.,
Landslides, Proceedings, 6th International Symposium on Landslides, Christchurch
:
Rotterdam
/
Brookfield, A.A. Balkema
, v.
3
, p.
1805
1841
.
Hutchinson
,
J.N.
Bhandari
,
R.K.
,
1971
,
Undrained loading, a fundamental mechanism of mudflows and other mass movements
:
Geotechnique
 , v.
21
, p.
353
358
.
Hutchinson
,
J.N.
Kojan
,
E.
,
1975
,
The Mayunmarca landslide of 25th April 1974, Peru: Serial No. 3124
 ,
Paris
,
UNESCO
,
49
p.
Hutchinson
,
J.N.
Bromhead
,
E.N.
Lupini
,
J.F.
,
1980
,
Additional observations on the landslides at Folkestone Warren
:
Quarterly Journal of Engineering Geology
 , v.
13
, p.
1
31
.
Jaekel
,
O.
,
1917
,
Neue Beiträge zur Tektonik des Rügener Steilufers
:
Zeitschrift der Deutschen Geologischen Gesellschaft
 , Bd.
69
, Heft
1
, p.
81
176
.
Jaekel
,
O.
,
1930
,
Das Kreideufer Rügens als tektonisches und glaciales problem
:
Abhandlungen aus dem geologisches-palaeontologischen Institut der Universität Greifswald
 , Bd.
8
, p.
3
24
plus 26 figures
.
Jenner
,
H.N.
Burfitt
,
R.H.
,
1974
,
Chalk: An engineering material
 :
Paper read at meeting of the Southern Area of the Institution of Civil Engineers
,
Brighton
, on
6th March, 1974
(unpublished)
.
Johnstrup
,
F.
,
1874
,
Om haevningsfaenomener i Møens Klint
:
Tidsskrift for populaere Fremstillinger af Naturvidenskaben, V raekke
 ,
42
p.
Jones
,
M.E.
,
1990
,
Hydrocarbon production from the North Sea Chalk: Geotechnical considerations
 :
Chalk, London
,
Thomas Telford
, p.
641
647
.
Jones
,
M.E.
Bedford
,
J.
Clayton
,
C.
,
1984
,
On deformation mechanisms in the Chalk
:
Journal of the Geological Society of London
 , v.
141
, p.
675
683
.
Jones
,
M.E.
Leddra
,
M.J.
Potts
,
D.
,
1990
,
Ground motions due to hydrocarbon production from the chalk
 :
Chalk, London
,
Thomas Telford
, p.
675
681
.
“K.B.,”
1828
,
Dover pig
:
Hone's table-book
 , v.
2
, p.
731
732
.
Keilhack
,
K.
,
1914
,
Geologische Wirkungen der Sturmflut der Jahrswende 1913/1914 auf die Küsten der Ostsee. 2. Rügen, Usedom und Wollin
:
Jahrbuch der Königlich Preussischen Geologischen Landesanstalt
 , Bd.
35
, Heft
2
, p.
115
124
.
Kennedy
,
W.J.
,
1985
,
Sedimentology of the Late Cretaceous and Early Paleocene Chalk Group, North Sea Central Graben
:
2nd North Sea Chalk Symposium
,
May 1985
,
Stavanger
,
Book 1
, p.
1
77
plus 18 figures and 35 plates
.
Lee
,
C.E.
,
1940
,
Chalk falls between Folkestone and Dover
:
The Railway Magazine
 , v.
2
, p.
531
534
.
Lennier
,
G.
,
1885
,
L'Estuaire de la Seine: Mémoire, notes et documents pour servir à l'étude de “L'Estuaire de la Seine”
:
Havre, Imprimerie du Journal Le Havre
 , v.
1
, p.
27
47
, 178–181.
Lesueur
,
C.-A.
,
1842
,
Courrier Français, Paris
 ,
17
septembre
.
Libert
,
L.
,
1906
,
L'éboulement des falaises de la Hève
:
La Nature
 , no.
1704
,
20
janvier
, p.
113
114
.
Liestøl
,
O.
,
1974
,
Avalanche plunge-pool effect
:
Norsk Polarinstitutt, Arbok 1972
 , p.
179
181
.
Longworth
,
T.I.
,
1970
,
A survey of falls in the Chalk cliffs of Ramsgate
 
[M.S. Thesis]
:
London
,
University of London, Imperial College, Soil Mechanics Section
,
41
p.
Lord
,
J.A.
Twine
,
D.
Yeow
,
H.
,
1993
,
Foundations in chalk: Funders Report /CP/13, CIRIA Project Report 11
 :
London
,
Construction Industry Research and Information Association
,
190
p.
Lower
,
M.A.
,
1855
,
Memorials of the town, parish and cinque-port of Seaford
 :
London
,
J.R. Smith; Lewes, R.W. Lower
,
78
p.
Lyell
,
C.
,
1875
,
Principles of geology
  (12th edition):
London
,
John Murray
,
2
vols.,
1004
p.
Mantell
,
G.A.
,
1833
,
The geology of the south-east of England
 :
London
,
Longman, Rees, Orme, Brown, Green and Longman
,
415
p.
plus 20 plates
.
Marshall
,
C.F.D.
,
1936
,
A history of the Southern Railway
 :
London
,
The Southern Railway Company
,
708
p.
Matthews
,
E.R.
,
1918
,
Coast erosion and protection
  (2nd edition, enlarged):
London
,
Charles Griffin & Company, Limited
,
195
p.
Matthews
,
E.R.
,
1934
,
Coast erosion and protection
  (3rd edition, revised):
London
,
Charles Griffin & Company, Limited
,
228
p.
May
,
V.J.
,
1971
,
The retreat of chalk cliffs
:
Geographical Journal
 , v.
137
, p.
203
206
.
McDakin
,
J.G.
,
1894
,
Coast erosion and landslips in the neighbourhood of Dover
:
South-eastern Naturalist
 , v.
1
, p.
132
136
.
McDakin
,
J.G.
,
1897
,
Report of Committee on coast erosion, 1896–97
:
Southeastern Naturalist
 , v.
2
, p.
5
6
.
McDakin
,
J.G.
,
1899
,
Coast erosion—Dover cliffs
:
British Association for the Advancement of Science
 , Reprinted
Dover
,
The Standard Office
.
McDakin
,
J.G.
,
1900
,
Coast erosion—Dover cliffs
 :
Dover
.
McDakin
,
J.G.
,
1910
,
Geological notes: Coast erosion
:
East Kent Scientific and Natural History Society
 , v.
9
, ser.
2
, p.
27
.
McDakin
,
J.G.
,
1911
,
Geological notes
:
East Kent Scientific and Natural History Society
 , v.
10
, ser.
2
, p.
13
.
McDakin
,
J.G.
,
1912
,
Geological notes
:
East Kent Scientific and Natural History Society
 , v.
11
, ser.
2
, p.
15
.
Mennessier
,
G.
Modret
,
D.
Lefebvre
,
P.
et al
1981
,
Carte Géologique au 1:50 000: Rue (Feuille XXI-6)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Meunier
,
S.
,
1897
,
Les éboulements de falaise en 1896
:
Connaissance de Dieppe et de sa region, no. 37, 4me année, déc, Éditions Bertout-Luneray
 , p.
19
20
.
Minikin
,
R.C.R.
,
1952
,
Coast erosion and protection
 :
London
,
Chapman and Hall, Dock and Harbour Authority
,
240
p.
Mortimore
,
R.N.
,
1986
,
Stratigraphy of the Upper Cretaceous White Chalk of Sussex
:
Proceedings of the Geologists’ Association
 , v.
97
, p.
97
139
.
Mortimore
,
R.N.
,
1987
,
Upper Cretaceous Chalk in the North and South Downs, England, a correlation
:
Proceedings of the Geologists’ Association
 , v.
98
, p.
77
86
.
Mortimore
,
R.N.
,
1990
,
Chalk or chalk?
 :
Chalk, London
,
Thomas Telford
, p.
15
45
.
Mortimore
,
R.N.
Fielding
,
P.M.
,
1990
,
The relationship between texture, density and strength of chalk
 :
Chalk, London
,
Thomas Telford
, p.
109
132
.
Mortimore
,
R.N.
Pomerol
,
B.
Foord
,
R.J.
,
1990a
,
Engineering stratigraphy and palaeogeography for the Chalk of the Anglo-Paris basin
 :
Chalk, London
,
Thomas Telford
, p.
47
62
.
Mortimore
,
R.N.
Roberts
,
L.D.
Jones
,
D.L.
,
1990b
,
Logging of chalk for engineering purposes
 :
Chalk, London
,
Thomas Telford
, p.
133
152
.
Neumayr
,
M.
Suess
,
F.E.
,
1920
,
Erdegeschichte. 1. Dynamische geologie
  (3rd edition):
Leipzig und Wien
,
543
p. plus 32 plates.
Nygaard
,
E.
,
1993
,
Denmark
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
186
207
.
Osman
,
C.W.
,
1917
,
The landslips of Folkestone Warren and the thickness of the Lower Chalk and Gault near Dover
:
Proceedings of the Geologists’ Association
 , v.
28
, p.
59
84
.
Parsons
,
A.W.
,
1966
,
Contribution to Discussion on Lewis and Croney, Chalk in earthworks and foundations
 :
London
,
Institution of Civil Engineers
, p.
102
104
.
Peake
,
N.B.
Hancock
,
J.M.
,
1970
,
The Upper Cretaceous of Norfolk
, in
Larwood
,
G.P.
Funnell
,
B.M.
, eds.,
The geology of Norfolk
 :
Norwich, England
,
The Geological Society of Norfolk
, p.
293
339
.
Perry
,
J.
,
1721
,
An account of the stopping of Daggenham Breach
 :
London
,
Benjamin Tooke
,
131
p.
Prêcheur
,
C.
,
1960
,
Le littoral de la Manche, de Sainte-Adresse à Ault: Étude morphologique
 :
Poitiers, France
,
S.F.I.L. et Imp. Marc Texier Reunies
,
138
p.
Rasmussen
,
H.W.
,
1979a
,
Bornholms undergrund: Det nordeuropaeiske kontinent
, in
Nørrevang
,
A.
Lundø
,
J.
, eds.,
Danmarks natur, Landskabernes opståen, Bind 1
 :
København
,
Politikens Forlag A/S
, p.
83
102
.
Rasmussen
,
H.W.
,
1979b
,
Blottede lag fra Danmarks undergrund: Skrivekridtet og kalkstenene
, in
Nørrevang
,
A.
Lundø
,
J.
, eds.,
Danmarks natur, Landskabernes opståen, Bind 1
 :
København
,
Politikens Forlag A/S
, p.
131
160
.
Rat
,
M.
Schaeffner
,
M.
,
1990
,
Classification of chalks and conditions of use in embankments
 :
Chalk, London
,
Thomas Telford
, p.
425
428
.
Reynolds
,
S.H.
,
1932
,
Landslips
:
Proceedings of the Bristol Natural History Society
 , v.
7
, ser.
4
, p.
352
357
.
Richter
,
R.
,
1936
,
Volkmar Wroost: Vorgänge der Kieselung am Beispiel des Feuersteins der Kreide
:
Abhandlung der senckenbergischen naturforschenden Gesellschaft
 , Bd.
432
, p.
68
.
Ricour
,
J.
Bonte
,
A.
Laveine
,
J-R
Leplat
,
J.
Souliez
,
G.
,
1987
,
Découverte géologique du Nord de la France
:
Orléans, BRGM [Bureau de Recherches Géologiques et Minières] Editions
 .
Robaszynski
,
F.
Amedro
,
F.
,
1986
,
The Cretaceous of the Boulonnais (France) and a comparison with the Cretaceous of Kent (United Kingdom)
:
Proceedings of the Geologists’ Association
 , v.
97
, p.
171
208
.
Roberts
,
G.
,
1840
,
An account of and guide to the mighty land-slip of Dowlands and Bindon, in the parish of Axmouth, near Lyme Regis, December, 25, 1839
 :
Lyme
,
Daniel Dunster
,
19
p.
Rowe
,
A.W.
,
1900
,
The zones of the White Chalk of the English coast. 1. Kent and Sussex
:
Proceedings of the Geologists’ Association
 , v.
16
, p.
289
368
.
Sassa
,
K.
,
1992
,
Landslide volume-apparent friction relationship in the case of rapid loading on alluvial deposits
:
Landslide News
 , no.
6
, p.
16
19
.
Sassa
,
K.
Fukuoka
,
H.
Lee
,
J.H.
Zhang
,
D.X.
,
1992
,
Measurement of the apparent friction angle during rapid loading by the high-speed high-stress ring shear apparatus: Interpretation of the relationship between landslide volume and the apparent friction during motion
, in
Bell
,
D.H.
, ed.,
Landslides, Proceedings of the 6th International Symposium on Landslides, Christchurch
:
Rotterdam
/
Brookfield, A.A. Balkema
, v.
1
, p.
545
552
.
Schack Pedersen
,
S.A.
,
1994
,
Skred pa Møns Klint
 :
Geologisk Nyt
,
University of Aarhus
, no.
3
, p.
3
5
.
Schoenfeld
,
J.
Grube
,
F.
,
1990
,
Chloride distribution pattern and fracturing in the white chalk of Lagerdorf/Holstein (NW-Germany): Implications for groundwater circulation in the chalk-overburden of a salt-diapir
 :
Chalk, London
,
Thomas Telford
, p.
591
596
.
Schroeder
,
C.
,
1995
,
Le “Pore Collapse”: Aspect particulier de l'interaction fluide-squelette dans les craies?
 :
Colloquium Mundanum 1995, Proceedings, Bruxelles, Groupement Belge de Mécanique des Roches
, p.
1.1.53
1.1.60
.
Slater
,
G.
,
1927
,
The structure of the disturbed deposits of Møens Klint, Denmark
:
Transactions of the Royal Society of Edinburgh
 , v.
55
,
Part II
, p.
289
302
plus 1 plate.
Smeaton
,
J.
,
1769
,
The report of John Smeaton, Engineer, upon the Harbour of Dover: Together with a plan of the said Harbour
 :
London
,
J. Hughs
, p.
6
8
.
“S.S.,”
1843
,
Great blast on the London and Dover Railway. Destruction of Round Down by gunpowder
:
Illustrated London News
 , v.
2
, no.
40
,
1st
April
, p.
76
78
.
Steinich
,
G.
,
1972
,
Endogene Tektonik in den Unter-Maastricht-Vorkommen auf Jasmund (Rügen)
:
Geologie
 , Jahrgang
20
, Beiheft
71/72
, p.
1
207
.
Surlyk
,
F.
,
1971
,
Geologie på Øerne. 1. Sydøstsjaelland og Møen – Varv Ekskursionfører Nr. 2, Skrivekridtklinterne på Møn
 :
København
,
Mineralogisk Museum
, p.
5
24
.
Surlyk
,
F.
,
1984
,
The Maastrichtian Stage in NW Europe, and its brachiopod zonation
:
Bulletin of the Geological Society of Denmark
 , v.
33
, p.
217
223
.
Ternet
,
M.Y.
,
1969
,
Carte géologique au 1:50000, Fécamp (Feuille XVIII-9)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Thorburn
,
A.
,
1977
,
Report on the problems of coastal erosion
 :
Lewes
,
East Sussex County Council
.
Toms
,
A.H.
,
1946
,
Folkestone Warren landslips: Research carried out in 1939 by the Southern Railway Company
:
Institution of Civil Engineers
 ,
Railway Paper 19
, p.
3
25
.
Trenter
,
N.A.
Warren
,
C.D.
,
1996
,
Further investigations at the Folkestone Warren landslide
:
Geotechnique
 , v.
46
, p.
589
620
.
van Rooijen
,
P.
,
1993
,
The Netherlands
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
170
185
.
Walcott
,
M.
,
1859
,
A guide to the coast of Sussex
 :
London
,
edward Stanford
.
Webster
,
T.
,
1814
,
On the freshwater formations in the Isle of Wight, with some observations on the strata over the Chalk in the south-eastern part of England
:
Geological Transactions
 , v.
1
, p.
161
254
.
Wheeler
,
W.H.
,
1902
,
The sea-coast
 :
London, New York and Bombay
,
Longmans, Green, and Co.
,
361
p.
Wilson
,
H.E.
,
1972
,
Regional geology of Northern Ireland
 :
Belfast
,
Her Majesty's Stationery Office
,
105
p.
Wood
,
A.M.M.
,
1946
,
History of Folkestone Warren
 :
(unpublished)
.
London
,
British Railways, Southern Region
.
Young
,
G.W.
,
1910
,
The chalk cliffs of Kent and Sussex
:
Geologists’ Association Jubilee Volume
 , p.
256
269
.

Acknowledgments

I am grateful for the general help of J.B. Burland, C.R.I. Clayton, S.G. Evans, the late H. Grace, J.M. Hancock, I.E. Higginbottom, O. Hungr, R.J. Jardine, M.E. Jones, J.A. Lord, R.N. Mortimore, and A.E. Skinner. I also thank the following for their help: with the English area, R.J. Allison, D.A. Baker, G.P. Birch, H. Bowdler, E.N. Bromhead, D. Brunsden, R. Castleden, A.A. Dibben, Dover and Folkestone Public Libraries, A.S. Gale, R. Gilbert, J. Gill, M.J. Leddra, Royal Engineers Library, Chatham, E.R. Shepard-Thorn, A. Stephens, Trinity House Lighthouse Service, P.M. Varley, C.D. Warren, and R.B.G. Williams; with northwest France, M. Arnould, J.C. Blivet, R. Delavigne, H. Evrard, M. Larchevêque, J-P. Lautridou, L. Rochet, and M. Villey; with eastern Denmark and southern Sweden, J. Bergström, S. Floris, N. Foged, P. Frykman, Nordiske Pressfoto, N.K. Ovesen, Politikens Forlag, K.S. Petersen, and L. Viberg; and with northern Germany, U. Boltze, C.M. Bristow, P. Broza, H. Cahill, J. Hanisch, F. Jakobsen, L. Jeschke, G. Katzung, H. Kliewe, R. Lampe, L. Lemby, G. Möbus, H. Nestler, H. Schnick, J. Schoenfeld, and J. Stötter. I gratefully acknowledge a grant of £200 from the University of London Central Research Fund toward the cost of the 1981 reconnaissance of the French coast.

Figures & Tables

Figure 1.

Extent of Upper Cretaceous outcrop in northwest Europe (after Choubert and Faure-Muret, 1976).

Figure 1.

Extent of Upper Cretaceous outcrop in northwest Europe (after Choubert and Faure-Muret, 1976).

Figure 2.

Plan and section defining morphological parameters of chalk falls and flows. Fahrböschung = tan−1 H/L; W = width of scar; Wd = max. width of debris, forumla = average width of debris; h = cliff height; H = overall height of failure; R = reach; L = overall length of failure, and forumla = average thickness of debris.

Figure 2.

Plan and section defining morphological parameters of chalk falls and flows. Fahrböschung = tan−1 H/L; W = width of scar; Wd = max. width of debris, forumla = average width of debris; h = cliff height; H = overall height of failure; R = reach; L = overall length of failure, and forumla = average thickness of debris.

Figure 3.

Key map of southeast English and northwest French coasts.

Figure 3.

Key map of southeast English and northwest French coasts.

Figure 4.

Incidence of major chalk falls and flows on coast of Sussex, England.

Figure 4.

Incidence of major chalk falls and flows on coast of Sussex, England.

Figure 5.

Sections of artificially induced fall at Seaford Head, Sussex (most westerly of three sections, giving maximum L/H. after Burgoyne, 1851). HWL, LWL = high, low water level, respectively; MSL is mean sea level.

Figure 5.

Sections of artificially induced fall at Seaford Head, Sussex (most westerly of three sections, giving maximum L/H. after Burgoyne, 1851). HWL, LWL = high, low water level, respectively; MSL is mean sea level.

Figure 6.

View of fall below Seaford Head, Sussex, in late 1980s (photo by Alan Stephens).

Figure 6.

View of fall below Seaford Head, Sussex, in late 1980s (photo by Alan Stephens).

Figure 7.

View of Beachy Head and lighthouse on June 12, 1975 (Cambridge University Collection of Air Photographs; copyright reserved).

Figure 7.

View of Beachy Head and lighthouse on June 12, 1975 (Cambridge University Collection of Air Photographs; copyright reserved).

Figure 8.

Incidence of major chalk falls and flows on coast of Kent.

Figure 8.

Incidence of major chalk falls and flows on coast of Kent.

Figure 16.

Destruction by blasting of Round Down. Kent (after “S.S.,” 1843).

Figure 16.

Destruction by blasting of Round Down. Kent (after “S.S.,” 1843).

Figure 17.

View of Dover Cliff and Castle from Langdon Bay, Kent (after Gilpin, 1804) (by permission of the British Library Reproductions).

Figure 17.

View of Dover Cliff and Castle from Langdon Bay, Kent (after Gilpin, 1804) (by permission of the British Library Reproductions).

Figure 18.

View of chalk fall of ca. 1961 at South Foreland, Kent, with some degree of flow, taken June 29, 1961 (acknowledgments to Aerofilms Ltd).

Figure 18.

View of chalk fall of ca. 1961 at South Foreland, Kent, with some degree of flow, taken June 29, 1961 (acknowledgments to Aerofilms Ltd).

Figure 19.

Section of chalk fall at Joss Bay, Kent (after Hutchinson, 1972). MHWS = mean high water springs. MLWS = mean low water springs.

Figure 19.

Section of chalk fall at Joss Bay, Kent (after Hutchinson, 1972). MHWS = mean high water springs. MLWS = mean low water springs.

Figure 20.

View of chalk fall of March 5, 1947, at West Cliff, Ramsgate, Kent (after Longworth, 1970).

Figure 20.

View of chalk fall of March 5, 1947, at West Cliff, Ramsgate, Kent (after Longworth, 1970).

Figure 21 (on this and following page).

A–C: Incidence of major chalk falls and flows on coast of France between Sainte Adresse and Ault, and around Cap Blanc-Nez. A = Cap de la Hève to Etretat; B = Yport to Pourville-s-Mer; C = Dieppe to Ault. See Figure 2 for L and H definitions, and Table 4 for details of most mobile chalk flows, F1–F9.

Figure 21 (on this and following page).

A–C: Incidence of major chalk falls and flows on coast of France between Sainte Adresse and Ault, and around Cap Blanc-Nez. A = Cap de la Hève to Etretat; B = Yport to Pourville-s-Mer; C = Dieppe to Ault. See Figure 2 for L and H definitions, and Table 4 for details of most mobile chalk flows, F1–F9.

Figure 22.

View of cliffs east-northeast of Cap Fagnet (in background). France, taken September 1981 (my photo).

Figure 22.

View of cliffs east-northeast of Cap Fagnet (in background). France, taken September 1981 (my photo).

Figure 23.

View of Le Chien Neuf, taken September 1981 (my photo).

Figure 23.

View of Le Chien Neuf, taken September 1981 (my photo).

Figure 24.

View of chalk flow of ca. 1980 near Saint Valery-en-Caux (after Evrard and Sinelle, 1981).

Figure 24.

View of chalk flow of ca. 1980 near Saint Valery-en-Caux (after Evrard and Sinelle, 1981).

Figure 25.

View of remains of pre-1986 chalk flow in cliffs west of Le Tréport (Bureau de Recherches Géologiques et Minières, 1986).

Figure 25.

View of remains of pre-1986 chalk flow in cliffs west of Le Tréport (Bureau de Recherches Géologiques et Minières, 1986).

Figure 26.

Stratigraphy involved in French chalk flows between Saint Adresse and Ault (* = generally after Evrard and Sinelle, 1981). γdmin = minimum dry density. γd = dry density.

Figure 26.

Stratigraphy involved in French chalk flows between Saint Adresse and Ault (* = generally after Evrard and Sinelle, 1981). γdmin = minimum dry density. γd = dry density.

Figure 27.

View of Cap Blanc-Nez (acknowledgments to Artaud Freres, Carquefou-Nantes).

Figure 27.

View of Cap Blanc-Nez (acknowledgments to Artaud Freres, Carquefou-Nantes).

Figure 28.

General view of eastern cliffs of Møns Klint, Denmark (acknowledgments to Nordisk Pressefoto, København).

Figure 28.

General view of eastern cliffs of Møns Klint, Denmark (acknowledgments to Nordisk Pressefoto, København).

Figure 29.

Incidence of major chalk falls and flows on east coast of Møns Klint. Key: 1, possible mobile chalk flow (cf); 2, mobile cf; 3, mobile cf, with reach known; 4, possible moderate cf; 5, moderate cf; 6, moderate chalk fall; 7, fall of glacial material (broken lines indicate uncertain location).

Figure 29.

Incidence of major chalk falls and flows on east coast of Møns Klint. Key: 1, possible mobile chalk flow (cf); 2, mobile cf; 3, mobile cf, with reach known; 4, possible moderate cf; 5, moderate cf; 6, moderate chalk fall; 7, fall of glacial material (broken lines indicate uncertain location).

Figure 33.

General view in July 1996, of cliffs to south of Kollicker Ort on east coast of Rügen, Germany (my photo).

Figure 33.

General view in July 1996, of cliffs to south of Kollicker Ort on east coast of Rügen, Germany (my photo).

Figure 34.

Incidence of major chalk falls and flows on east coast of Rügen (Jasmund and Cap Arkona). Key: 1, possible mobile chalk flow (cf); 2, mobile cf with reach known; 3, moderate cf with reach known; 4, moderate cf; 5, fall of glacial material.

Figure 34.

Incidence of major chalk falls and flows on east coast of Rügen (Jasmund and Cap Arkona). Key: 1, possible mobile chalk flow (cf); 2, mobile cf with reach known; 3, moderate cf with reach known; 4, moderate cf; 5, fall of glacial material.

Figure 36.

Relationship of chalk flow incidence to distributions of porosity (dry density) and hardness against stratigraphy for various coastal chalk regions of Britain, Denmark, and north Germany. Ur Chk = upper chalk; Mid Chk = middle chalk; Lr Chk = lower chalk.

Figure 36.

Relationship of chalk flow incidence to distributions of porosity (dry density) and hardness against stratigraphy for various coastal chalk regions of Britain, Denmark, and north Germany. Ur Chk = upper chalk; Mid Chk = middle chalk; Lr Chk = lower chalk.

Figure 37.

Distribution of types of chalk in Anglo-Paris Basin (after Mortimore et al., 1990a).

Figure 37.

Distribution of types of chalk in Anglo-Paris Basin (after Mortimore et al., 1990a).

Figure 38.

Brecciated chalk in putty chalk matrix, in chalk flow debris below eastern part of Abbot's Cliff, Kent, September 1996 (my photo). Tape case is 170 mm in diameter.

Figure 38.

Brecciated chalk in putty chalk matrix, in chalk flow debris below eastern part of Abbot's Cliff, Kent, September 1996 (my photo). Tape case is 170 mm in diameter.

Figure 39.

Stress path for undrained triaxial compression test with pore-pressure measurement on Butser Hill chalk of porosity of 36.9%–37.3% (M. Leddra, Imperial College, 1988, personal commun.).

Figure 39.

Stress path for undrained triaxial compression test with pore-pressure measurement on Butser Hill chalk of porosity of 36.9%–37.3% (M. Leddra, Imperial College, 1988, personal commun.).

Figure 40.

Incidence of coastal chalk flows in relation to state of tide.

Figure 40.

Incidence of coastal chalk flows in relation to state of tide.

Figure 41.

Comparison of volumes and hydrogeology involved in failures in nearly vertical cliffs of hard chalk and in less steep cliffs of softer chalk. O.D. = ordnance datum ~ mean sea level, GWT = groundwater level. See Figure 2 for definitions of L and H.

Figure 41.

Comparison of volumes and hydrogeology involved in failures in nearly vertical cliffs of hard chalk and in less steep cliffs of softer chalk. O.D. = ordnance datum ~ mean sea level, GWT = groundwater level. See Figure 2 for definitions of L and H.

Figure 42.

Elevation of Kent cliffs between Folkestone and Kingsdown (after Hutchinson, 1991) (γd values supplied by R.N. Mortimore).

Figure 42.

Elevation of Kent cliffs between Folkestone and Kingsdown (after Hutchinson, 1991) (γd values supplied by R.N. Mortimore).

Figure 43.

Plot of L/H against H for more mobile coastal chalk flows of northwest Europe. N = highest cliff fall in Kent without flow sliding (Fig. 12, Hutchinson, 1988). See Figure 2 for definitions of L and H.

Figure 43.

Plot of L/H against H for more mobile coastal chalk flows of northwest Europe. N = highest cliff fall in Kent without flow sliding (Fig. 12, Hutchinson, 1988). See Figure 2 for definitions of L and H.

Figure 44.

Plot of H/L (inverse of mobility) against log of debris volume for chalk flows from Kentish cliffs (Hutchinson, 1988, 1991). See Figure 2 for definitions of L and H.

Figure 44.

Plot of H/L (inverse of mobility) against log of debris volume for chalk flows from Kentish cliffs (Hutchinson, 1988, 1991). See Figure 2 for definitions of L and H.

Figure 45.

Incidence of coastal chalk flows by time of year.

Figure 45.

Incidence of coastal chalk flows by time of year.

Table 1.

Stratigraphy of the Upper Cretaceous (After Birkelund, et al., 1984)

Stage
Maastrichtian
Campanian
Santonian
Coniacian
Turanian
Cenomanian
Stage
Maastrichtian
Campanian
Santonian
Coniacian
Turanian
Cenomanian

Note: Relationships to the earlier, now informal terminology of Lower, Middle and Upper Chalk are shown subsequently in Figure 36.

Table 2.

Members of the Flow Slide Family

Loose sandSubaqueousCohesionlessIncreasing disturbance needed to generate high + Δu
    Natural, sea bed (Zeeland coast)
    Artificial, hydraulic fill (Fort Peck)Subaerial
Loose debris
    Natural, scree (Modalen)
    Artificial waste dumps (Aberfan, Jupille, etc.)
Quick claySome cohesion or cementation
    Scandinavia and Canada
Weathered igneous rock
    Kaolinite (Cornwall), pumice, etc.
Loes
    Khansu Province (China)
    Dushanbe (Tajikistan)
Soft chalk
    Kent and northwest Europe
Loose sandSubaqueousCohesionlessIncreasing disturbance needed to generate high + Δu
    Natural, sea bed (Zeeland coast)
    Artificial, hydraulic fill (Fort Peck)Subaerial
Loose debris
    Natural, scree (Modalen)
    Artificial waste dumps (Aberfan, Jupille, etc.)
Quick claySome cohesion or cementation
    Scandinavia and Canada
Weathered igneous rock
    Kaolinite (Cornwall), pumice, etc.
Loes
    Khansu Province (China)
    Dushanbe (Tajikistan)
Soft chalk
    Kent and northwest Europe

Note: Table after Hutchinson (1995). All involve generation of high + Δu (liquefaction) produced by collapse of metastable, saturated or near-saturated structure in all or part of the mass (largely after Hutchinson, 1988)

Table 3.

Most Mobile Chalk Flows on the Sussex and Kent Coasts

Chalk flow and numberApproximate (Fig. 2)Approximate L/HDate and location
L (m)H (m)
Sussex
E1Debris formed natural groyne?1848 Monkey's Cliff
Kent
E26281504.191915 Folkestone Warren
E3Debris ran out over beach?1877
E4Debris ran well out to sea?1910 Abbot's Cliff
E54711313.601911
E6Debris formed natural groyne?pre-1769
E74421453.051988
E8 (blasted)4701223.851843 Round Down
E9An immense fall?1772 Shakespeare Cliff
E10>36689>4.111912
E11An extremely large fall?1897
E12Debris formed natural groyne?1834
E13Debris formed natural groyne?pre-1767
E14Debris formed natural groyne?1690–1710
E15 (3 cases)Debris formed natural groyne?1760–1774 Dover Cliffs
E16288933.101910 South Foreland
E17405685.961970 Saint Margaret's Bay
E18R = 366??pre-1895
E19410795.191905
E20268833.231910
E21Larger than 1905 chalk flow?1870
Chalk flow and numberApproximate (Fig. 2)Approximate L/HDate and location
L (m)H (m)
Sussex
E1Debris formed natural groyne?1848 Monkey's Cliff
Kent
E26281504.191915 Folkestone Warren
E3Debris ran out over beach?1877
E4Debris ran well out to sea?1910 Abbot's Cliff
E54711313.601911
E6Debris formed natural groyne?pre-1769
E74421453.051988
E8 (blasted)4701223.851843 Round Down
E9An immense fall?1772 Shakespeare Cliff
E10>36689>4.111912
E11An extremely large fall?1897
E12Debris formed natural groyne?1834
E13Debris formed natural groyne?pre-1767
E14Debris formed natural groyne?1690–1710
E15 (3 cases)Debris formed natural groyne?1760–1774 Dover Cliffs
E16288933.101910 South Foreland
E17405685.961970 Saint Margaret's Bay
E18R = 366??pre-1895
E19410795.191905
E20268833.231910
E21Larger than 1905 chalk flow?1870

Note: L = length; H = height. The above figures (particularly for L), apart from those for E2 and E8, which are based on accurate survey, and E7, for which there was an approximate survey, are largely approximate estimates from newspapers and local scientific societies.

Table 4.

Most Mobile Chalk Flows Between Saint Jouin-Bruneval and Ault, Northwest France

Chalk flow numberApproximate (Fig. 2)Approximate L/HLocation
L (m)H (m)
F1350784.49Yport(E)
F2320664.85Saint Valery (E)
F3315714.44Saint Valery (E)
F4140344.12Saint Aubin (W)
F5165404.13Saint Aubin (E)
F6400994.04Saint Martin Plage (W)
F7350993.54Saint Martin Plage (W)
F84501024.41Penly
F9345983.52Le Tréport (W)
Chalk flow numberApproximate (Fig. 2)Approximate L/HLocation
L (m)H (m)
F1350784.49Yport(E)
F2320664.85Saint Valery (E)
F3315714.44Saint Valery (E)
F4140344.12Saint Aubin (W)
F5165404.13Saint Aubin (E)
F6400994.04Saint Martin Plage (W)
F7350993.54Saint Martin Plage (W)
F84501024.41Penly
F9345983.52Le Tréport (W)

Note: L = length: H = height. Because the above values are scaled from uncorrected vertical aerial photographs in Bureau de Recherches Géologiques et Minières (1986), they are generally to some degree approximate. An exception to this is case F8, which is based on scaling from the debris lobe shown on the 1:50 000 geological map for Dieppe-Est (Bignot, et al., 1978). Further data could be obtained from the 1:25 000 topographical maps and other vertical air photos.

Table 5.

Average Dry Densities for Strata on the English and French Sides of the Channel Tunnel

StratumEngland densities (kN/m3)France densities (kN/m3)
Middle Chalk16.3818.44
White Chalk17.0619.61
Grey Chalk—Upper19.0319.81
Grey Chalk—Lower20.1021.18
Chalk Marl—Upper20.3021.28
Chalk Marl—Lower19.1219.91
Glauconitic Marl20.4021.58
Upper Gault17.5518.44
Lower Gault17.3619.61
StratumEngland densities (kN/m3)France densities (kN/m3)
Middle Chalk16.3818.44
White Chalk17.0619.61
Grey Chalk—Upper19.0319.81
Grey Chalk—Lower20.1021.18
Chalk Marl—Upper20.3021.28
Chalk Marl—Lower19.1219.91
Glauconitic Marl20.4021.58
Upper Gault17.5518.44
Lower Gault17.3619.61

Note: Data after Channel Tunnel Study Group (1966), v. III, Section X, p. 10–16.

Contents

References

References Cited

“A.F.,”
1913
,
Møens Klint
:
Møens Turistforening, Stege
 ,
30
p.
Andersen
,
S.A.
,
1944
,
Det Danske Landskabs Historie: Danmarks Geologie i Almenfattelig Fremstilling (2. Staerkt for0gede udgave). Bind 1, Undergrunden
 :
København
,
Populaer-Videnskabeligt Forlag
,
480
p.
plus Tidstavler 1 a–g
.
Anonymous
,
1813
,
Fall at East Dean: Gentleman's Magazine
:
London, D. Henry and R. Cave
 , v.
83
, p.
278
.
Anonymous
,
1836
,
A walk under the Shakespeare and other poems
 :
London
,
W. Prescott; Dover, B. Steill
.
Anonymous
,
1840a
,
Great fall of cliff at Dover
 :
The Times
,
London
,
6th
February
, p.
5
.
Anonymous
,
1840b
,
Encroachments and recessions of the sea
:
Civil Engineer and Architect's Journal, Scientific and Railway Gazette
 , v.
3
, p.
167
168
.
Anonymous
,
1843a
,
Destruction of the Round-Down-Cliff by gunpowder
 :
The Times
,
London
,
27th
January
, p.
5
.
Anonymous
,
1843b
,
Another great blast at Dover
 :
The Times
,
London
,
3rd
March
, p.
5
.
Anonymous
,
1850
,
Grand explosion at Seaford Cliff
:
Illustrated London News, 21st September
 , v.
17
, p.
242
.
Anonymous
,
1853
,
The Bay of Dover and the cliffs of Dover
 :
The Times
,
London
,
8th
March
, p.
8
.
Anonymous
,
1868
,
Møens Klint
 :
Møens Avis
,
Møen
, post-
25
December
.
Anonymous
,
1869
,
Dronningestolens Nedstortning
 :
Faedrelandet
,
København
, no.
7
.
Anonymous
,
1875
,
L'éboulement de Dieppe
 :
Le Monde Illustré
,
Paris
,
19e année
, no.
933
,
27th
February
, p.
152
.
Anonymous
,
1877
,
The landslip
 :
Folkestone Chronicle
,
Folkestone
,
20th
January
, p.
5
.
Anonymous
,
1895
,
Falling cliffs in Kent
 :
The Standard
,
London
,
8th
June
, p.
4
Anonymous
,
1896
,
La villa Bellevue à Dieppe
 :
Le Monde Illustré
,
Paris
,
40e année
, no.
2072
,
12th
December
, p.
377
.
Anonymous
,
1897
,
Herne Bay Press
,
Herne Bay
,
13th
March
, p.
7
.
Anonymous
,
1905a
,
St. Margaret's Bay, Dover
:
Nature
 , v.
71
, no.
1837
, p.
253
and 279.
Anonymous
,
1905b
,
The landslips near Dover
 :
The Times
,
London
,
16th
January
, p.
7
.
Anonymous
,
1905c
,
The great landslide at Dover: The fallen cliff
:
Illustrated London News, 21st January
 , v.
126
, p.
82
.
Anonymous
,
1905d
,
Fall of cliff at St. Margaret's
 :
The Dover Express and East Kent News
,
Dover
, Friday,
13th
January
,
1905
, p.
5
.
Anonymous
,
1910
,
Fall of cliff
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
18th
November
, p.
10
.
Anonymous
,
1912a
,
Ground disturbed by rain. Fall of cliff between Dover and Folkestone
 :
The Times
,
London
,
2nd
January
, p.
6
.
Anonymous
,
1912b
,
The landslide near Dover
 :
The Times
,
London
,
3rd
January
, p.
4
.
Anonymous
,
1912c
,
Great fall at Abbott's Cliff
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
5th
January
.
Anonymous
,
1914
,
Great fall of cliff at one of the Seven Sisters
 :
Eastbourne Gazette
,
Eastbourne
,
22nd
April
, p.
5
.
Anonymous
,
1915a
,
Great landslide. Line wrecked in Warren
 :
Folkestone Express
,
Folkestone
,
25th
December
, p.
8
.
Anonymous
,
1915b
,
Big landslide in Folkestone Warren
 :
Folkestone, Hythe, Sandgate, and Cheriton Herald
,
Folkestone
,
25th
December
, p.
2
.
Anonymous
,
1933
,
Fall of cliff near Dover. Result of heavy rains
 :
The Times
,
London
,
18th
November
, p.
12
.
Anonymous
,
1937a
,
Thames again rising
 :
The Times
,
London
,
8th
February
, p.
12
.
Anonymous
,
1937b
,
Another cliff fall
 :
The Dover Express and East Kent News
,
Dover
,
12th
February
, p.
5
, 9.
Anonymous
,
1937c
,
Big cliff fall
 :
The Dover Express and East Kent News
,
Dover
,
Friday
,
5th
March
, p.
2
, 9.
Anonymous
,
1947
,
White cliffs of Dover
 :
The Evening Standard
,
London
,
12th
February
, p.
1
.
Anonymous
,
1970a
,
Cliff fall turned sea white
 :
East Kent Mercury
,
Deal
,
9th
April
, p.
1
.
Anonymous
,
1970b
,
Big cliff fall follows rain, snow, and frost – and more may follow
 :
The Dover Express and East Kent News
,
Dover
,
10th
April
, p.
3
.
Anonymous
,
1979
,
Heavy cliff fall
 :
The Daily Telegraph
,
London
,
16th
January
, p.
3
.
Anonymous
,
1980a
,
Sprang for livet pa Møns Klint under Kaempeskred
 :
Møns Tidende
,
Stege
,
7th
July
.
Anonymous
,
1980b
,
Tysk familie sekunder fra døden ved nyt klinte-skred
 :
Møns Tidende
,
Stege
,
11th
July
.
Anonymous
,
1986
,
Golf course hit as cliffs crash into sea
 :
Evening Argus
,
Brighton
,
16th
July
, p.
1
.
Anonymous
,
1988
,
Landslip halts trains
 :
Folkestone, Hythe and District Herald
,
Folkestone
,
29th
January
, p.
3
.
Anonymous
,
1999
,
Photo caption
:
Geoscientist
 , v.
9
, no.
2
, February 1999, p.
3
.
Beckett
,
1929
,
Perils of Beachy Head
:
Sussex County Magazine
 , v.
3
, p.
630
633
.
Benek
,
R.
,
1969
,
Rezente Rutschung am Kap Arkona auf Rügen
:
Zeitschrift für angewandte Geologie, Sonderbeilage
 , v.
15
, no.
9
, p. between 472 & 473.
Bialek
,
M.
Grosse
,
M.
Foucaud
,
M.
,
1969
,
Recul des falaises du cap d'Antifer au Tréport (entre 1830 et 1966)
:
Direction Départementale de l'Equipement, Service maritime, Section 2, Arrondissement Maritime de Dieppe
 .
Bignot
,
G.
1971
,
Carte géologique au 1:50000, Dieppe-Ouest (Feuille XIX-8)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bignot
,
G.
Auffret
,
J-P.
Monciardini
,
C.
Moal
,
A.
,
1978
,
Carte géologique au 1:50000, Dieppe-Est (Feuille XX-8)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Birch
,
G.P.
,
1990
,
Engineering geomorphological mapping for cliff stability: Chalk
 :
London
,
Thomas Telford
, p.
545
549
.
Birch
,
G.P.
Warren
,
C.D.
,
1996
,
The cliffs behind the Channel Tunnel workings: Chapter 7
, in
Harris
,
C.S.
Hart
,
M.B.
Varley
,
P.M.
Warren
,
C.D.
, eds.,
Engineering geology of the Channel Tunnel
 :
London
,
Thomas Telford
, p.
76
87
.
Birkelund
,
T.
Hancock
,
J.M.
Hart
,
M.B.
Rawson
,
P.F.
Remane
,
J.
Robaszynski
,
F.
Schmid
,
F.
Surlyk
,
F.
,
1984
,
Cretaceous stage boundaries: Proposals
:
Bulletin of the Geological Survey of Denmark
 , v.
33
, p.
3
20
.
Bishop
,
A.W.
,
1973
,
The stability of tips and spoil heaps
:
Quarterly Journal of Engineering Geology
 , v.
6
, p.
335
376
.
Bjerrum
,
L.
,
1971
,
Subaqueous slope failures in Norwegian fjords
 :
Norwegian Geotechnical Institute
Publication 88
, p.
1
8
.
Bloomfield
,
J.P.
Brewerton
,
L.J.
Allen
,
D.J.
,
1995
,
Regional trends in matrix porosity and dry density of the Chalk of England
:
Quarterly Journal of Engineering Geology
 , v.
28
,
Supplement 2
, p.
S131
S142
.
Boltenhagen
,
C.
Menillet
,
F.
Ternet
,
Y.
,
1968
,
Carte géologique au 1:50000, Montivilliers-Etretat (Feuille XVII-9-10)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bonte
,
A.
Broquet
,
P.
Destombes
,
J.-P.
Somme
,
J.
Hatrival
,
J.-N.
et al
,
1971
,
Carte Géologique au 1:50000, Marquise (Feuille XXI-3)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Bonte
,
A.
Broquet
,
P.
Destombes
,
J.-P.
et al
,
1985
,
Carte géologique au 1:50000, Boulogne-sur-Mer (Feuille 2104)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Böttcher
,
H.
,
1985
,
Stoffliche Zusammensetzung und Eigenschaften des Rohstoffes Kreide
:
Zeitschrift für angewandte Geologie
 , Band
31
, Heft
3
, p.
62
67
.
Botter
,
B.J.
,
1985
,
Pore collapse measurements on chalk cores
, in
Second North Sea Chalk Symposium
:
Stavanger, Norway
,
Book 2
, p.
1
12
plus 13 figs.
Bourdillon
,
F.W.
,
1884
,
Beachy Head
:
Transactions of the Eastbourne Natural History Society, New Series
 , v.
1
, p.
4
21
.
Briquet
,
A.
,
1930
,
Le Littoral du Nord de la France et son evolution morphologique
 :
Paris
,
Librairie Armand Colin
,
439
p.
Broquet
,
P.
Beun
,
N.
Dupuis
,
C.
et al
,
1984
,
Carte géologique au 1:50000, St-Valery-sur-Somme-Eu (Feuille 2007–2107)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Buisson
,
M.
,
1952
,
Les glissements de la falaise de Sainte-Adresse
:
Annales de l'Institut Technique du Bâtiment et des Travaux Publics, 50th année
 , no.
59
, Supplement, p.
1130
1145
.
Bureau de Recherches Géologiques et Minières
,
1986
,
Étude du littoral Haut Normand entre Le Havre et Le Tréport: Rapport General
 :
Maisons-Alfort
,
Laboratoire Central d'Hydraulique de France
.
Burgoyne
,
J.F.
,
1851
,
Paper 13. 1. Preliminary observations on the mining operations for blowing down the cliff near Seaford, on the coast of Sussex, in August and September, 1850
:
Professional Papers of Royal Engineers, New Series
 , v.
1
, p.
68
69
.
Casagrande
,
A.
,
1936
,
Characteristics of cohesionless soils affecting the stability of slopes and earth fills
:
Journal of the Boston Society of Civil Engineers
 , v.
23
, p.
13
32
.
Castleden
,
R.
,
1982
,
Landform Guides No. 2: Classic landforms of the Sussex coast
 :
Sheffield
,
The Geographical Association
,
39
p.
Chambers
,
G.F.
,
1862
,
Contributions towards a history of Eastbourne
:
Sussex Archaeological Collections
 , v.
14
, p.
119
137
.
Channel Tunnel Study Group
,
1966
,
Channel Tunnel: Site investigations in the Strait of Dover 1964–1965
:
Courbevoie, France, and London, Channel Tunnel Study Group
 , v.
3
, Section 10, p.
1
36
.
Choubert
,
G.
Faure-Muret
,
A.
,
1976
,
Geological World Atlas
 :
Paris
,
UNESCO
,
scale 1:10000000
.
Christensen
,
P.R.
Andersen
,
H.C.
, eds., n.d. (ca.
1959
),
Gads Små Egnsboger, Møn
:
G.E.C. Gads Forlag
 ,
64
p.
Church
,
H.K.
,
1981
,
Excavation Handbook
 :
New York
,
McGraw Hill Book Company
,
954
p.
Clarke
,
R.H.
,
1977
,
Earthworks in soft chalk: Performance and prediction
:
The Highway Engineer
 ,
March
, p.
18
21
.
Clayton
,
C.R.I.
,
1978a
,
Chalk as fill
 
[Ph.D. thesis]
:
Guildford
,
University of Surrey
,
489
p.
Clayton
,
C.R.I.
,
1978b
,
A note on the effects of density on the results of Standard Penetration Tests in chalk
:
Geotechnique
 , v.
26
, p.
119
122
.
Clayton
,
C.R.I.
,
1983
,
The influence of diagenesis on some index properties of chalk in England
:
Geotechnique
 , v.
33
, p.
225
241
.
Clayton
,
C.R.I.
,
1990
,
The mechanical properties of the Chalk
 :
Chalk, London
,
Thomas Telford
, p.
213
232
.
Corner
,
G.D.
,
1980
,
Avalanche impact landforms in Troms, north Norway
:
Geografiska Annaler
 , v.
62
A, p.
1
10
.
Dassargues
,
A.
Monjoie
,
A.
,
1993
,
Belgium
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
153
169
.
Davison
,
C.
,
1924
,
A history of British earthquakes
 :
Cambridge
,
Cambridge University Press
,
416
p.
D'Heur
,
M.
,
1993
,
The Chalk as a hydrocarbon reservoir
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of Northwest Europe
 :
Oxford
,
Clarendon Press
, p.
251
266
.
Dodsley
,
R.
Dodsley
,
J.
,
1772
,
Annual Register
 :
London
,
R. Dodsley and J. Dodsley
.
Ellson
,
G.
,
1940
,
Contribution to Discussion on Duvivier
:
Journal of the Institution of Civil Engineers
 , v.
14
, p.
428
431
.
Evrard
,
H.
Sinelle
,
C.
,
1981
,
Stabilité des Falaises du Pays de Caux
:
Le Grand-Quevilly, Centre d'Etudes Techniques de l'Equipment
 ,
87
p.
Evrard
,
H.
Sinelle
,
C.
,
1987
,
La stabilité des falaises du Pays de Caux-Normandie: Actes du Colloque Mer et Littoral couple à risque
:
Biarritz
 ,
11–13
Septembre
, p.
84
91
.
Foged
,
N.
,
1994
,
Møns Klint: Evaluering af skred og sikringstiltag foreløbig vurdering
 :
Lyngby, Geoteknisk Institut, Rapport 1, 1994-08-08
,
12
p.
plus 6 figures
.
Frome
,
R.E.
,
1851
,
Paper 13. 2. Mining operations at Seaford
:
Professional Papers of Royal Engineers, New Series
 , v.
1
, p.
69
79
.
Frykman
,
P.
,
1994
,
Variability in petrophysical properties in Upper Maastrichtian chalk outcrops at Stevns, Denmark: A contribution to the EFP-92 Project: Stochastic modelling of petrophysical properties in chalk
 :
Copenhagen
,
Geological Survey of Denmark
,
DGU [Danmarks Geologiske Undersøgelse] Service report
, no.
38
,
10
p.
plus 20 figures
.
Geikie
,
A.
,
1903
,
Text-book of geology
  (4th edition):
London and New York
,
Macmillan and Co Ltd.
,
2
vols.,
1472
p.
Gilbert
,
R.
,
1964
,
Changing face of Beachy Head
 :
Eastbourne Gazette
,
Eastbourne
,
12th
August
, p.
21
.
Gilpin
,
W.
,
1804
,
Observations on the coasts of Hampshire, Sussex, and Kent … made in the summer of the year 1774
 :
London
,
T. Cadell & W. Davies
,
135
p.
Gripp
,
K.
,
1947
,
Jasmund und Möen, eine glacial-morphologische Untersuchung
:
Erdkunde, Band
 
1
, p.
175
187
.
Gustafsson
,
O.
,
1993
,
Sweden
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
208
219
.
Håkansson
,
E.
,
1971
,
Geologi på Øyerne, 1, Sydostsjaelland og Møn–Varv ekskursionfører Nr 2, Stevns Klint
 :
Mineralogisk Museum
,
København
, p.
25
36
.
Hancock
,
J.M.
,
1986
,
Cretaceous
, in
Glennie
,
K.W.
, ed.,
Introduction to the petroleum geology of the North Sea
 :
Oxford
,
Blackwell
, p.
161
178
.
Harris
,
E.
,
1943
,
Submerged and reclaimed coastal Sussex
:
Sussex County Magazine
 , v.
17
, p.
260
262
.
Heim
,
A.
,
1932
,
Bergsturz und menschenleben
:
Beiblatt zur Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich
 , no.
20
,
Jahrgang 77
, p.
1
218
.
Herrig
,
E.
,
1995
,
Die Kreide und das Pleistozän von Jasmund, Insel Rügen (Ostsee)
, in
Katzung
,
G.
Hüneke
,
H.
Obst
,
K.
, eds.,
Geologie des südlichen Ostseeraumes—Umwelt und Untergrund, 147
 .
Haupt-ver-sammlung der Deutschen Geologischen Gesellschaft Exkursionsführer
,
4–6
Oktober
,
Greifswald
, p.
91
113
.
Higginbottom
,
I.E.
Fookes
,
P.G.
,
1970
,
Engineering aspects of periglacial features in Britain
:
Quarterly Journal of Engineering Geology
 , v.
3
, p.
85
117
.
Hintze
,
V.
,
1937
,
Møens Klints Geologi
 :
København
,
C.A. Reitzels Forlag
,
410
p.
Hobbs
,
N.B.
Healy
,
P.R.
,
1979
,
Piling in chalk
 :
London
,
Construction Industry Research and Information Association
,
DoE and CIRIA Piling Development Group, Report PG6
,
126
p.
Howell
,
J.
,
1874
,
On the geology of Brighton
:
Proceedings of the Geologists’ Association
 , v.
3
, p.
168
188
.
Hsü
,
K.J.
,
1975
,
On Sturzstroms: Catastrophic debris streams generated by rockfalls
:
Geological Society of America Bulletin
 , v.
86
, p.
129
140
.
Hungr
,
O.
,
1995
,
A model for the runout analysis of rapid flow slides, debris flows, and avalanches
:
Canadian Geotechnical Journal
 , v.
32
, p.
610
623
.
Hurtig
,
T.
,
1959a
,
Der grosse Kreideausbruch auf Rügen im Jahre 1958
:
Natur und Heimat
 , Jahrgang
8
, Heft
9
, p.
460
463
.
Hurtig
,
T.
,
1959b
,
Über die Uferzerstörungen an der Steilküste von Rügen (NSG Jasmund) im Jahre 1958
:
Naturschutzarbeit und naturkundliche Heimatforschung
 , Heft
2
, p.
2
6
.
Hurtig
,
T.
,
1961
,
Der grosse Bergrutsch 1958 am dem Kreidesteilufer nördlich Sassnitz auf Rügen
:
Geographische Berichte, Mitteilungen der Geographischen Gesellschaft der Deutschen Demokratischen Republik
 , Heft
18
, p.
1
8
.
Hurtig
,
T.
,
1964
,
Eine Naturkatastrophe am Kreidsteilufer von Rügen
:
Natur und Museum
 , Bd.
94
, Heft
9
, p.
331
342
.
Hutchinson
,
G.R.
,
1843
,
Account of the demolition and removal by blasting of a portion of the Round Down Cliff, near Dover, in January, 1843
:
Professional Papers of Royal Engineers, Quarto Series
 , v.
6
, p.
188
203
.
Hutchinson
,
J.N.
,
1965
,
A survey of the coastal landslides of Kent
 :
Watford
,
Building Research Station
,
Note No. EN 11/65
,
117
p.
Hutchinson
,
J.N.
,
1969
,
A reconsideration of the coastal landslides at Folkestone Warren, Kent
:
Geotechnique
 , v.
19
, p.
6
38
.
Hutchinson
,
J.N.
,
1972
,
Field and laboratory studies of a fall in Upper Chalk cliffs at Joss Bay, Isle of Thanet
, in
Stress-strain behaviour of soils, Proceedings of the Roscoe Memorial Symposium, Cambridge
:
Henley-on-Thames, G.T. Foulis & Co. Ltd
, p.
692
706
.
Hutchinson
,
J.N.
,
1980
,
Various forms of cliff instability arising from coastal erosion in the U.K.
:
Fjellsprengningsteknikk-Bergmekanikk-Geoteknikk 1979, 19.1–19.3. Trondheim, Tapir, for Norsk Jord-og-Fjellteknisk Forbund tillknyttet NIF
 
Hutchinson
,
J.N.
,
1983
,
Engineering in a landscape: Inaugural Lecture
 ,
9th
October
,
1979
:
London
,
Imperial College, University of London
,
12
p.
Hutchinson
,
J.N.
,
1984
,
Landslides in Britain and their countermeasures
:
Journal of Japan Landslide Society
 , v.
21-1
, p.
1
24
.
Hutchinson
,
J.N.
,
1986
,
A sliding-consolidation model for flow slides
:
Canadian Geotechnical Journal
 , v.
23
, p.
115
126
.
Hutchinson
,
J.N.
,
1988
,
General report: Morphological and geotechnical parameters of landslides in relation to geology and hydrogeology
, in
Bonnard
,
C.
, ed.,
Landslides, Proceedings, 5th International Symposium on Landslides, Lausanne
:
Rotterdam
/
Brookfield, A.A. Balkema
, p.
3
35
.
Hutchinson
,
J.N.
,
1991
,
Lower Shakespeare Site: Cliff stability and run-out study
:
Report to Engineering and Power Development Consultants Limited
 ,
October
,
33
p.
plus 16 figures (unpublished)
.
Hutchinson
,
J.N.
,
1995
,
Keynote Paper: Landslide hazard assessment
, in
Bell
,
D.H.
, ed.,
Landslides, Proceedings, 6th International Symposium on Landslides, Christchurch
:
Rotterdam
/
Brookfield, A.A. Balkema
, v.
3
, p.
1805
1841
.
Hutchinson
,
J.N.
Bhandari
,
R.K.
,
1971
,
Undrained loading, a fundamental mechanism of mudflows and other mass movements
:
Geotechnique
 , v.
21
, p.
353
358
.
Hutchinson
,
J.N.
Kojan
,
E.
,
1975
,
The Mayunmarca landslide of 25th April 1974, Peru: Serial No. 3124
 ,
Paris
,
UNESCO
,
49
p.
Hutchinson
,
J.N.
Bromhead
,
E.N.
Lupini
,
J.F.
,
1980
,
Additional observations on the landslides at Folkestone Warren
:
Quarterly Journal of Engineering Geology
 , v.
13
, p.
1
31
.
Jaekel
,
O.
,
1917
,
Neue Beiträge zur Tektonik des Rügener Steilufers
:
Zeitschrift der Deutschen Geologischen Gesellschaft
 , Bd.
69
, Heft
1
, p.
81
176
.
Jaekel
,
O.
,
1930
,
Das Kreideufer Rügens als tektonisches und glaciales problem
:
Abhandlungen aus dem geologisches-palaeontologischen Institut der Universität Greifswald
 , Bd.
8
, p.
3
24
plus 26 figures
.
Jenner
,
H.N.
Burfitt
,
R.H.
,
1974
,
Chalk: An engineering material
 :
Paper read at meeting of the Southern Area of the Institution of Civil Engineers
,
Brighton
, on
6th March, 1974
(unpublished)
.
Johnstrup
,
F.
,
1874
,
Om haevningsfaenomener i Møens Klint
:
Tidsskrift for populaere Fremstillinger af Naturvidenskaben, V raekke
 ,
42
p.
Jones
,
M.E.
,
1990
,
Hydrocarbon production from the North Sea Chalk: Geotechnical considerations
 :
Chalk, London
,
Thomas Telford
, p.
641
647
.
Jones
,
M.E.
Bedford
,
J.
Clayton
,
C.
,
1984
,
On deformation mechanisms in the Chalk
:
Journal of the Geological Society of London
 , v.
141
, p.
675
683
.
Jones
,
M.E.
Leddra
,
M.J.
Potts
,
D.
,
1990
,
Ground motions due to hydrocarbon production from the chalk
 :
Chalk, London
,
Thomas Telford
, p.
675
681
.
“K.B.,”
1828
,
Dover pig
:
Hone's table-book
 , v.
2
, p.
731
732
.
Keilhack
,
K.
,
1914
,
Geologische Wirkungen der Sturmflut der Jahrswende 1913/1914 auf die Küsten der Ostsee. 2. Rügen, Usedom und Wollin
:
Jahrbuch der Königlich Preussischen Geologischen Landesanstalt
 , Bd.
35
, Heft
2
, p.
115
124
.
Kennedy
,
W.J.
,
1985
,
Sedimentology of the Late Cretaceous and Early Paleocene Chalk Group, North Sea Central Graben
:
2nd North Sea Chalk Symposium
,
May 1985
,
Stavanger
,
Book 1
, p.
1
77
plus 18 figures and 35 plates
.
Lee
,
C.E.
,
1940
,
Chalk falls between Folkestone and Dover
:
The Railway Magazine
 , v.
2
, p.
531
534
.
Lennier
,
G.
,
1885
,
L'Estuaire de la Seine: Mémoire, notes et documents pour servir à l'étude de “L'Estuaire de la Seine”
:
Havre, Imprimerie du Journal Le Havre
 , v.
1
, p.
27
47
, 178–181.
Lesueur
,
C.-A.
,
1842
,
Courrier Français, Paris
 ,
17
septembre
.
Libert
,
L.
,
1906
,
L'éboulement des falaises de la Hève
:
La Nature
 , no.
1704
,
20
janvier
, p.
113
114
.
Liestøl
,
O.
,
1974
,
Avalanche plunge-pool effect
:
Norsk Polarinstitutt, Arbok 1972
 , p.
179
181
.
Longworth
,
T.I.
,
1970
,
A survey of falls in the Chalk cliffs of Ramsgate
 
[M.S. Thesis]
:
London
,
University of London, Imperial College, Soil Mechanics Section
,
41
p.
Lord
,
J.A.
Twine
,
D.
Yeow
,
H.
,
1993
,
Foundations in chalk: Funders Report /CP/13, CIRIA Project Report 11
 :
London
,
Construction Industry Research and Information Association
,
190
p.
Lower
,
M.A.
,
1855
,
Memorials of the town, parish and cinque-port of Seaford
 :
London
,
J.R. Smith; Lewes, R.W. Lower
,
78
p.
Lyell
,
C.
,
1875
,
Principles of geology
  (12th edition):
London
,
John Murray
,
2
vols.,
1004
p.
Mantell
,
G.A.
,
1833
,
The geology of the south-east of England
 :
London
,
Longman, Rees, Orme, Brown, Green and Longman
,
415
p.
plus 20 plates
.
Marshall
,
C.F.D.
,
1936
,
A history of the Southern Railway
 :
London
,
The Southern Railway Company
,
708
p.
Matthews
,
E.R.
,
1918
,
Coast erosion and protection
  (2nd edition, enlarged):
London
,
Charles Griffin & Company, Limited
,
195
p.
Matthews
,
E.R.
,
1934
,
Coast erosion and protection
  (3rd edition, revised):
London
,
Charles Griffin & Company, Limited
,
228
p.
May
,
V.J.
,
1971
,
The retreat of chalk cliffs
:
Geographical Journal
 , v.
137
, p.
203
206
.
McDakin
,
J.G.
,
1894
,
Coast erosion and landslips in the neighbourhood of Dover
:
South-eastern Naturalist
 , v.
1
, p.
132
136
.
McDakin
,
J.G.
,
1897
,
Report of Committee on coast erosion, 1896–97
:
Southeastern Naturalist
 , v.
2
, p.
5
6
.
McDakin
,
J.G.
,
1899
,
Coast erosion—Dover cliffs
:
British Association for the Advancement of Science
 , Reprinted
Dover
,
The Standard Office
.
McDakin
,
J.G.
,
1900
,
Coast erosion—Dover cliffs
 :
Dover
.
McDakin
,
J.G.
,
1910
,
Geological notes: Coast erosion
:
East Kent Scientific and Natural History Society
 , v.
9
, ser.
2
, p.
27
.
McDakin
,
J.G.
,
1911
,
Geological notes
:
East Kent Scientific and Natural History Society
 , v.
10
, ser.
2
, p.
13
.
McDakin
,
J.G.
,
1912
,
Geological notes
:
East Kent Scientific and Natural History Society
 , v.
11
, ser.
2
, p.
15
.
Mennessier
,
G.
Modret
,
D.
Lefebvre
,
P.
et al
1981
,
Carte Géologique au 1:50 000: Rue (Feuille XXI-6)
:
Orléans-la-Source, Bureau de Recherches Géologiques et Minières
 .
Meunier
,
S.
,
1897
,
Les éboulements de falaise en 1896
:
Connaissance de Dieppe et de sa region, no. 37, 4me année, déc, Éditions Bertout-Luneray
 , p.
19
20
.
Minikin
,
R.C.R.
,
1952
,
Coast erosion and protection
 :
London
,
Chapman and Hall, Dock and Harbour Authority
,
240
p.
Mortimore
,
R.N.
,
1986
,
Stratigraphy of the Upper Cretaceous White Chalk of Sussex
:
Proceedings of the Geologists’ Association
 , v.
97
, p.
97
139
.
Mortimore
,
R.N.
,
1987
,
Upper Cretaceous Chalk in the North and South Downs, England, a correlation
:
Proceedings of the Geologists’ Association
 , v.
98
, p.
77
86
.
Mortimore
,
R.N.
,
1990
,
Chalk or chalk?
 :
Chalk, London
,
Thomas Telford
, p.
15
45
.
Mortimore
,
R.N.
Fielding
,
P.M.
,
1990
,
The relationship between texture, density and strength of chalk
 :
Chalk, London
,
Thomas Telford
, p.
109
132
.
Mortimore
,
R.N.
Pomerol
,
B.
Foord
,
R.J.
,
1990a
,
Engineering stratigraphy and palaeogeography for the Chalk of the Anglo-Paris basin
 :
Chalk, London
,
Thomas Telford
, p.
47
62
.
Mortimore
,
R.N.
Roberts
,
L.D.
Jones
,
D.L.
,
1990b
,
Logging of chalk for engineering purposes
 :
Chalk, London
,
Thomas Telford
, p.
133
152
.
Neumayr
,
M.
Suess
,
F.E.
,
1920
,
Erdegeschichte. 1. Dynamische geologie
  (3rd edition):
Leipzig und Wien
,
543
p. plus 32 plates.
Nygaard
,
E.
,
1993
,
Denmark
, in
Downing
,
R.A.
Price
,
M.
Jones
,
G.P.
, eds.,
The hydrogeology of the Chalk of North-West Europe
 :
Oxford
,
Clarendon Press
, p.
186
207
.
Osman
,
C.W.
,
1917
,
The landslips of Folkestone Warren and the thickness of the Lower Chalk and Gault near Dover
:
Proceedings of the Geologists’ Association
 , v.
28
, p.
59