Abstract Tsunami catalogues provide important datasets in assessing the risk from infrequent but potentially high-impact events. Although the UK is located away from subduction zones (the most common origin of tsunamis), tsunamis have struck its shores, most notably those triggered by the prehistoric Storegga submarine landslide and the 1755 Lisbon earthquake. Since the major events of 2004 (Indian Ocean) and 2011 (Japan) tsunamis are in the public psyche, even if the risks to UK coasts are not. Due to this heightened awareness, many reported events are claimed to be tsunamis and the potential for tsunamis is increasingly included in risk planning; understanding the true frequency of tsunamis is therefore important. Within the UK, the evidence for tsunamis includes tide gauge readings, reported visual observations and interpretation of sedimentological features. Catalogues need to consider whether the event is a true tsunami in order to avoid a plethora of claims that confound risk assessments; for example, recent well-documented events generated by weather systems (meteotsunamis) provide a possible explanation for some historical events. A detailed examination of the impact of tsunamis upon the UK coast is provided, including examples of events triggered by the three primary causes of tsunamis: seismicity, submarine landslides and coastal landslides.

Abstract The cliffs along the Potomac River at Stratford Hall display extensive exposures of Miocene marine strata that belong successively to the Calvert, Choptank, St. Marys, and Eastover Formations. Within the lower part of this sequence, in the Calvert and Choptank Formations, there is well-developed cyclic stratigraphy. Above the Miocene units lies the marginal marine to deltaic Pleistocene Bacons Castle Formation, which is the highest and youngest formation exposed in the cliffs. The goals of this field trip guide are to (1) show the Miocene formations exposed in the cliffs and discuss the paleoenvironments within which they formed, (2) demonstrate the cyclicity in the Miocene marine formations and discuss its origin, (3) compare and contrast the section exposed at the Stratford and Nomini Cliffs with the classic Miocene Calvert Cliffs sequence exposed to the northeast in Calvert County, Maryland, and the Miocene sequence recovered in the Haynesville cores to the southeast in Richmond County, Virginia, (4) discuss and explain why a detailed correlation among these three places has been so difficult to attain, and (5) show typical lithologies of the Bacons Castle Formation and discuss the paleoenvironments in which they formed.

Estimating postglacial coastal sediment budgets is difficult as erosion has removed the landscape drowned by marine transgression and coastal positions through time are rarely known. In the Natural Environment Research Council (NERC)–funded Land Ocean Interaction Study, a model was built, based on detailed characterization of onshore-offshore bathymetric profiles (created by Holocene wave-base migration). Modeling of the pre-Holocene western North Sea land surface (west of 1°E and south of 54°N) and sea-level curves allow determination of the likely position of wave base and coast at any time during the late Holocene. The volumes of materials eroded from cliffs, wave action on the shoreface, and tidal scour associated with erosion of pits (e.g., Inner Silver Pit) from different coastal areas have been estimated. The average annual contribution of sediment per meter length of coast is higher than some recent erosion rates would suggest, but appears consistent with the volumetric difference between the modeled end-Pleistocene surface and the present topographic-bathymetric surface. With other models, outputs would suggest that less than 5% of the Humber Holocene is likely to be of fluvial origin—a percentage corroborated by detailed geochemical and mineralogical provenance studies of the estuarine fill. The model suggests that more sediment has been released from the shoreface than from cliffs per unit length of coastline throughout the Holocene; this is an important finding for coastal managers, as this pattern is likely to continue and because the shore-face cannot be effectively protected from erosion.

The high carbonate island of Niue has attracted the attention of scientists since the early European exploration of the South Pacific, but its extensive karst and numerous caves have so far received little attention. Our investigation recognizes two main types of caves on Niue: (1) steeply inclined, terraced, flank-margin caves that formed at the seaward edge of a migrating freshwater lens and that breach the vertical cliffs on the leeward side of the island, and (2) flat-roofed, water-table caves consisting of interconnected passages that developed at the paleo–water table and contain dissolution features caused by alternating vadose and phreatic conditions. The Niuean caves contain a large variety of both active and fossil speleothems, the forms and styles of which are controlled by the hydrodynamics of vadose and phreatic waters, the physical properties of the carbonate cap, and the tectono-eustatic history of the island. The stalagmites are composed exclusively of calcite and show pronounced laminations consisting of alternating light and dark couplets, likely representing austral summer and winter growth, respectively. The mean growth rate of stalagmites from coastal flank-margin caves (∼0.34 mm/yr) is faster by about a factor of 1.5 relative to stalagmites from inland water-table caves. In general, vadose and phreatic waters fall on the regional δ 18 O-δD meteoric water line, and their dissolved carbon is primarily derived from soil CO 2 . A material balance suggests that cave deposits act as sinks for Mg, Sr, Na, and CO 2 during the recharge of the aquifer. The Niuean caves and their speleothems offer exceptional opportunities for investigating problems bearing on the regional tectono-eustatic history and paleoseismicity of the neighboring Tonga Trench, and answer questions concerning the prehistoric rhythms and irregularities of El Niño–Southern Oscillation.

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.