Avellino Eruption

Avellino Eruption
Thousands of footprints in the surge ash deposit of the Avellino Eruption testify to an en masse exodus from the devastated zone
Volcano	Mount Vesuvius
Date	2nd millennium B.C.
Type	Plinian
Location	Naples, Italy 40°49′N 14°26′E / 40.817°N 14.433°E / 40.817; 14.433Coordinates: 40°49′N 14°26′E / 40.817°N 14.433°E / 40.817; 14.433
VEI	6
Impact	Disturbed and preserved Bronze Age settlements in the area
Hut at the site of the village

The Avellino eruption of Mount Vesuvius refers to a Plinian-type eruption that occurred in the 2nd millennium BC and is estimated to have had a VEI of 6. It is the source of the Avellino Pumice (Italian: Pomici di Avellino) deposits named from the comune of Avellino in Campania where they have been found extensively.

"Assessment of volcanological factors" in one scientific study reconstruct a minimum eruption time of 3 hours in which an initial explosion raised a column of 23 km (75,000 ft) and deposited about 0.32 km³ of white pumice ("the white pumice phase"), while a second, more intense explosion raised a column of 31 km (102,000 ft) depositing 1.25 km³ of grey pumice ("the grey pumice phase"). These pumices appearing in Apulian pottery can be used to establish relative chronology of pottery phases.

A 2008 study of the lithofacies (deposits from the eruption) distinguishes three phases. Pyroclastic flows (PDC's) of Phases 1 and 2 were generated by "magmatic fragmentation" and had "small dispersal areas" mainly on the slopes of Vesuvius. Phase 3 was created by "phreatomagmatic fragmentation," in which clastic fragments are driven by superheated steam from ground water mixed with the other gases released from the magma. The authors characterize Phase 3 as "the most voluminous and widespread in the whole of Somma-Vesuvius' eruptive history." Some facies a few cm thick were found 25 km (16 mi) from the source. The vent was 2 km (1.2 mi) west of today's center.

The overall results of the Avellino Eruption were catastrophic and widespread. The deposit thickness of ash and other eruptive material ranges from 15m close to the vent to 50 cm around Avellino, as well as creating a subaquaeous debris-flow in the bay of Naples.

The date of the Avellino Eruption remains to be determined with a precision greater than about 500 years within the framework of the Early/Middle Bronze Age. A range of 2000 BC — 1500 BC includes the great majority of estimates. Ample opportunity to obtain Carbon-14 dates from charcoal and soil buried under the deposits has existed and still exists. Sporadic radiocarbon dating continues, with each scientist claiming to have obtained "the latest." Consistency with previous and subsequent work remains elusive. Since a real and very precise calendar date of the eruption must have existed, variation in estimations can only be the result of limitations to the carbon-dating method, which, given a plenitude of reliably emplaced samples, can only produce a date within a window of roughly 500 years in a maximum elapsed time of roughly 4000 years or 1/8 (12.5%).