Abstract The Lattari Mountains (a limestone ridge about 20 km south of Vesuvius) received 1–2.5 m of fallout from the famous Plinian eruption of ad 79. As demonstrated by many residual outcrops of thick volcanoclastic debris-flow and alluvial deposits (referred to here as the Durece unit), the pyroclastic fall was soon followed by rapid erosion and landsliding that produced (1) decametre-scale aggradation of some narrow valley floors; (2) reactivation of alluvial fans; and (3) growth of new fan-deltas (extending as far as 500 m) at the coast. This response was primarily due to the steep topography of the area and the high erodability of the pyroclastic materials (light and cohesionless pumice fragments). Several geo-archaeological data indicate that the accelerated sedimentation had a duration of the order of decades and was followed by rapid dissection of the Durece unit deposits and fast dismantling by wave action of the newly created fan-deltas. This case highlights the need to consider the possibly catastrophic reaction of fluvial and coastal systems to large explosive eruptions, even in non-volcanic terrains at some distance from the volcano.

The destruction of the cities of Pompeii and Herculaneum and the villas in the surrounding area by the eruption of Vesuvius in A.D. 79 preserved a unique body of information about flora and fauna, such as is available at no other ancient site. Root cavities can be emptied of lapilli and casts made of roots that were growing at the time of the eruption. Planting patterns also help to identify the plants raised. Soil contours, which vary according to the crop, are preserved by the lapilli just as they were in A.D. 79. Carbonized, or partially carbonized fruit, nuts, vegetables, root material, branches, and twigs are at times preserved. Ancient pollen also furnishes valuable evidence. The bones of mammals and the shells of mollusks and echinoderms are often found, as well as a few bird bones. Paintings preserve the actual appearance of the ancient plants, mammals, birds, and marine animals. Unfortunately, much of this evidence has been lost, for until recently excavators have not been interested in such finds. Today scientific garden archaeology carefully salvages all such evidence. The excavated evidence is then studied, together with the comments of the ancient writers and in the light of modern practices, which strikingly continue those of antiquity. Many scientists, in diverse disciplines, have cooperated in identifying and interpreting this valuable evidence. This chapter briefly reports the excavation of six different types of sites, three at Pompeii and three at nearby villas, and discusses specific examples of the various types of evidence of flora and fauna preserved by Vesuvius at these sites.

Abstract Volcanological studies in the Bronze Age settlement of Akrotiri (Santorini, Greece) and in the Roman towns of Pompeii and Herculaneum (Vesuvius, Italy) have provided information about the precursory phenomena preceding the Minoan and AD 79 Plinian eruptions and the impact of the eruptive products on the human settlements. The Akrotiri settlement was badly damaged by earthquakes before the onset of the eruption. A building debris layer, related to these earthquakes, covers the Minoan soil. The fallout pumice bed, mantling the ruins, freezes a state of partial destruction of the settlement. The deposition of the following pyroclastic flows completed the covering of the site. Strong seismicity also occurred during the opening and the Plinian phases. At the Herculaneum and Pompeii excavations clear evidence of strong pre- and syn-eruptive earthquakes is absent. Herculaneum, just 7 km west of the crater of Vesuvius, was destroyed by several pyroclastic flows, which buried the town under 20 m of deposits. Pompeii was covered by a 3 m thick blanket of pumice fall deposit. Distal dilute and turbulent ash clouds reached the town toward the end of the Plinian phase, killing all remaining inhabitants. The following turbulent cloud related to the onset of the caldera collapse completely destroyed the town, which was successively covered by the final phreatomagmatic products of the eruption.

Abstract A high-resolution (IKB-Seistec) seismic survey calibrated with gravity-core data, off the Amalfi coast, a rocky coastal area on the southern side of the Sorrento Peninsula (Italy), documents the internal stratigraphic architecture of a series of small fan-deltas that develop at the mouth of major bedrock streams. The fan-delta system mostly postdates the Plinian eruption of Vesuvius of ad 79 and displays various phases of development associated with periods of high sediment supply from the adjacent river basins. During these periods landscape-mantling loose pyroclastic deposits (mostly air-fall tephra from Vesuvius) were quickly eroded and delivered to the continental shelf by sheet wash and flash flood events. Depositional processes on the foresets were dominated by sediment gravity flows originating from hyperpycnal river flow and pyroclastic fall deposits. This in turn created favourable conditions for sea-floor instability, soft sediment failure, slumping and sliding, which characterize the deltaic stratigraphic architecture. The intermittently increased sediment yield during the various phases of the evolution of the fan-delta system was probably influenced also by the morphoclimatic regime. This may have resulted in varying rates of progradation of the delta foresets, tentatively correlated with the main climatic oscillations of the last 2000 years. The Amalfi fan-delta system represents a small-scale analogue for larger flood-dominated fan-deltas of the world and may be regarded as a useful example for a better understanding of inner-shelf, mixed siliciclastic–volcaniclastic fan-delta systems in the stratigraphic record.

Volcaniclastic debris flows generated in drainage basins of the Apennine mountains of southern Campania in response to pyroclastic fall deposition from four Holocene eruptions of Somma-Vesuvius: Avellino (3.8 ka), A.D. 79, A.D. 472, and A.D. 1631. These syneruptive debris flows are lithologically homogeneous and contain more than 90% of material from the parental eruption. They differ from inter-eruptive debris flows recognized in the area, which contain mixed lithologies of juvenile material (i.e., volcanic material from different eruptions). Diffuse rill erosion generated fines-rich volcaniclastic flows (mudflows), whereas partial saturation of coarse ash and lapilli generated coarser-grained debris flows. Lithofacies analysis shows that debris flows predominate versus hyperconcentrated flows and normal stream-flow deposits. Debris-flow deposits are massive, matrix supported, and have a gravelly-sandy texture. Large blocks are scarce due to their absence in the pyroclastic source material. Lithofacies association indicates that volcaniclastic debris-flow deposits aggraded rapidly by superimposition of different surges that spontaneously developed within the flow. Bulk-flow density ranges from 1840 to 2260 kg/m 3 (mean 2035 ± 207 kg/m 3 ). Geological data supported some considerations of hazard assessment in the study area and indicate that the syneruptive volcaniclastic flows stopped distally on active alluvial fans.

Abstract The temperature of the deposits ( T dep ) emplaced by the pyroclastic density current (PDC) generated by the seven major explosive eruptions from Somma–Vesuvius during the last 22 kyr were investigated using the thermal remanent magnetization (TRM) of lithic clasts embedded within the deposits. New data are presented for the Pomici di Base, Greenish Pumice, Mercato and 1631 AD deposits and compared to the literature data from the Avellino, 79 AD-Pompeii and 472 AD-Pollena eruptions. The T dep mainly fall in the range 270–370 °C and no significant correlation is evidenced between sedimentological features, eruptive and depositional processes and the final T dep . The admixture of ambient air during the run-out appears the most effective process to cool the temperature of the ash and gases of the PDC, and is therefore the main factor affecting the deposit temperature.

Abstract Depending on their magnitude and location, volcanic eruptions have the potential to become major social and economic disasters (e.g. Tambora, Indonesia, 1815; Vesuvius, Italy, AD 79; Soufriere Hills Volcano, Montserrat, 1995-present).One of the challenges for the volcanology community is to improve our understanding of volcanic processes so as to achieve successful assessments and mitigation of volcanic hazards, which are traditionally based on volcano monitoring and geological records. Geological records are crucial to our understanding of eruptive activity and history of a volcano, but often do not provide a comprehensive picture of the variation of volcanic processes and their effects on the surrounding area. The geological record is also typically biased towards the largest events, as deposits from smaller eruptions are often removed by erosion. Numerical modelling and probability analysis can be used to complement direct observations and to explore a much wider range of possible scenarios. As a result, numerical modelling and probabilistic analysis have become increasingly important in hazard assessment of volcanic hazards (e.g. Barberi et al. 1990 ; Heffter & Stunder 1993 ; Wadge et al. 1994 , 1998 ; Hill et al. 1998 ; Iverson et al. 1998 ; Searcy et al. 1998 ; Canuti et al. 2002 ). Reliable and comprehensive hazard assessments of volcanic This paper offers a detailed review of common approaches for hazard assessments of tephra dispersion. First, the main characteristics of tephra dispersion and tephra hazards are recounted. A critical use of field data for a