Syneruptive features and sedimentary processes associated with pyroclastic currents entering the sea: the ad 79 eruption of Vesuvius, Bay of Naples, Italy

Abstract

The ad 79 Plinian eruption of Vesuvius that buried Pompeii and Herculaneum began with pumice falls deposited towards the SE of the volcano followed by pyroclastic currents directed towards the SW. These currents reached Herculaneum and rapidly entered the sea, forming a fan. The interpretation of seismic reflection profiles and gravity cores collected off Herculaneum documents a submarine fan-shaped pyroclastic body at 10–140 m water depth that we interpret as the submarine counterpart of the onshore pyroclastic current deposits. This fan, c . 0.3 km 3 in volume, displays a chaotic seismic facies that changes seaward to parallel reflectors and then to wavy reflectors. Gravity cores reveal a succession consisting of centimetre-thick sand- or silt-sized ash couplets followed by a graded gravelly sand-sized bed up to 180 cm thick, containing shell fragments and beach-derived pebbles, overlain by centimetre-thick graded and laminated sandy ash layers. The depositional textures and sedimentary structures of the submarine pyroclastic fan have been interpreted as the product of the interactions between pyroclasts, water waves and tsunamis induced by the ad 79 pyroclastic density currents into the Bay of Naples.

Fluid Vents, Flank Instability, and Seafloor Processes along the Submarine Slopes of the Somma-Vesuvius Volcano, Eastern Tyrrhenian Margin

“…19 ka). The post-LGM (PLMG) succession is characterized by frequent tephra layers (dark reflectors) intercalated with reworked deposits deriving from lateral collapses ("whitened" reflectors) [9,15,30]. Main bedrock contacts located below the PLGM show indented or sharp margins, thus allowing discrimination of volcanic/volcaniclastic deposits from the sedimentary basement.…”

“…The second deposit is emplaced between the Sebeto River Plain and Somma-Vesuvius, and it is dated about 3.5 ka BP. In the central sector, the occurrence of a series of pyroclastic flow units generated by the Plinian eruption that destroyed Pompei and Ercolano (79 AD) has been documented [9]. It was also proposed that the pyroclastic flow deposits entering the seawater during the 79 AD eruption generated a tsunami in Naples Bay [9].…”

“…Integrated multibeam echosounder (MBES) bathymetry, magnetometric profiles, high-resolution seismic reflection data, and Remote Operated Vehicle (ROV) inspections help to establish a better A focus of our research is also the recognition of shallow sub-seafloor structures and seafloor morphologies linked to the underwater dynamics of the peripheral sector of the volcanic complex. Documented features include distal magnetized bodies occurring on the outer submarine slopes of the volcano, seafloor doming coupled with diapir-like morphostructures (pagodas) associated with soft sediment deformation by active degassing, and wavy bedforms [9] resulting from extensive seafloor instability along the submerged slopes. Particularly, we discuss the origin of the "Bocca dei Pescatori" (Fisherman's hole), a sharp, relatively deep semicircular depression located in the proximity of the Somma-Vesuvius coast.…”

Seismic Stratigraphy and Marine Magnetics of the Naples Bay (Southern Tyrrhenian Sea, Italy): The Onset of New Technologies in Marine Data Acquisition, Processing and Interpretation

“…The AD 79 Plinian eruption of Vesuvius that buried Pompei and Herculaneum began with pumice falls followed by pyroclastic currents (Milia et al, 2008). These currents reached Herculaneum and entered the sea, forming a fan.…”

Gravity instabilities in the Dohrn Canyon (Bay of Naples, Southern Tyrrhenian Sea): potential wave and run-up (tsunami) reconstruction from a fossil submarine landslide

“…This segment of the Italian continental margin displays evidence of the latest Neogene-Quaternary interplay between tectonics and volcanism, as well as of the depositional processes largely developing as a consequence of frequent and large volcano-sedimentary supply. The major morphological features revealed by the 3D digital maps are: i) the system of marine canyons (Dohrn and Magnaghi) that cut the continental slope at a depth between 250 m and 1100 m; ii) the continental slope system of the Ischia volcanic structure (Chiocci & de Alteriis 2006;Aiello et al 2009a); iii) the onshore and offshore volcanoes of the Campi Flegrei; iv) the rugged seafloor area of the outer shelf of the city of Naples (Banco della Montagna - Sacchi et al 2000;D'Argenio et al 2004); v) the debris flow/avalanche deposits on the inner continental shelf off Mt Vesuvius (Milia et al 1998(Milia et al , 2008, laterally grading into the "Torre del Greco" volcanic structure (Aiello et al 2010).…”