|
||||||||||||||
Eruptions before
A.D. 79 |
||||||||||||||
Vesuvio's eruptive history prior to the AD 79 eruption is not historically documented, and only the major explosive (Plinian) events have been reconstructed fairly well in recent years. It is known that during the past ~25,000 years, the volcano has had eight Plinian eruptions, three of them during the Holocene: "Ottaviano", or "Mercato" (~8000 BP), "Avellino" (~3750 BP) and "Pompei" (AD 79). The intervening activity is relatively poorly constrained but there appear to have been periods of prolonged or intermittent, small to moderate scale activity similar to that after the AD 79 and 1631 eruptions, as well as several sub-Plinian (A.D. 472 or 1631 size) events. Much still has to be learned. A forthcoming issue of the Journal of Volcanology and Geothermal Research will be dedicated to Somma-Vesuvio, with an emphasis on the earlier (pre-AD 79) history of the volcano. The Plinian events before AD 79 will be described in short summaries in the following, based mainly on Santacroce (1987), Rolandi et al. (1993b, 1993c), and going stratigraphically upwards. 1) 25,000 BP "Codola" Plinian eruption 2) 22,500 BP "Sarno" Plinian eruption 3) 17,000 BP "Basal" Plinian eruption 4) 15,500 BP "Greenish" ("Verdoline") Plinian eruption 5) 11,400 BP "Lagno Amendolare" Plinian (?) eruption 6) 8000 BP "Mercato" or "Ottaviano" Plinian eruption 7) 3750 BP "Avellino" Plinian eruption The "Avellino" eruption was
very similar to the AD 79 "Pompei" eruption,
regarding erupted volumes and the course of eruptive phases. The initial
activity was violently phreatomagmatic and produced pyroclastic surge
and phreatoplinian deposits. A Plinian phase ensued, ejecting almost 3
km^3 of pumice, initially more evolved white and grading upwards into
more mafic gray pumice. Fallout occurred in a sector ENE of the volcano,
leaving a deposit more than 50 cm thick at Avellino, about 35 km from
Vesuvio. Close to the volcano, on its NE slope, the fall deposits are
up to 3 m thick. |
||||||||||||||
Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology" |
||||||||||||||
Page
set up in January 1996, last modified on 3 February 2000
|