Publication Date:
2021-12-16
Description:
Ash samples from tephra layers correlated with the Pomici di Avellino (Avellino Pumice) eruption
of Somma-Vesuvius were collected in distal archives and their composition and particle
morphology investigated in order to infer their behaviour of transportation and deposition.
Differences in composition and particle morphologies were recognised for ash particles belonging
to the magmatic Plinian and final phreatomagmatic phases of the eruption. The ash particles were
dispersed in opposite directions during the two different phases of the eruption, and these directions
are also different from that of coarse-grained fallout deposits. In particular, ash generated during
magmatic phase and injected in the atmosphere to form a sustained column shows a prevailing SE
dispersion, while ash particles generated during the final phreatomagmatic phase and carried by
pyroclastic density currents show a general NW dispersion. These opposite dispersions indicate an
ash dispersal influenced by both high and low atmosphere dynamics. In particular, the magmatic
ash dispersal was first driven by stratospheric wind towards NE and then the falling particles
encountered a variable wind field during their settling, which produced the observed preferential SE
dispersal. The wind field encountered by the rising ash clouds that accompanied the pyroclastic
density currents of the final phreatomagmatic phase was different with respect to that encountered
by the magmatic ash, and produced a NW dispersal. These data demonstrate how ash transportation
and deposition are greatly influenced by both high and low atmosphere dynamics. In particular,
fine-grained particles transported in ash clouds of small-scale pyroclastic density currents may be
dispersed over distances and cover areas comparable with those injected into the stratosphere by
Plinian, sustained columns. This is a point not completely addressed by present day mitigation plans
in case of renewal of activity at Somma-Vesuvius, and can yield important information also for
other volcanoes potentially characterised by explosive activity.
Description:
Published
Description:
On line First
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
3.5. Geologia e storia dei sistemi vulcanici
Description:
3.6. Fisica del vulcanismo
Description:
JCR Journal
Description:
open
Keywords:
Pomici di Avellino eruption
;
ash dispersal
;
atmosphere dynamics
;
volcanic hazard
;
04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
;
04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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