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Magma Dynamics and Volcanic Processes within Active Craters and Basaltic Conduits Revealed by Textural and Compositional Features of Erupted Ash

Event Type: 
Event Date: 
17 Mar 2017
EOS Seminar Room - N2-01B-28
Massimo Pompilio
About the speaker: 

Massimo Pompilio is a Senior Scientist at Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Pisa. Massimo's research career focuses on the study of mechanisms of genesis, ascent, eruption and emplacement of basaltic magmas. These arguments have been studied on the basis of:

  • field observations and measurements and petrological monitoring carried during eruptions of last three decades of Stromboli and Etna volcanoes;
  • volcanological, petrological and geochemical investigations on products of Italian volcanoes (Mt.Etna , Hyblean plateau, Stromboli and Ustica islands and Sicily Channel seamounts, Phlegrean Fields, Capraia), El Hierro (Canary Island, Spain), Eyjafjallajokull (Iceland) e North Victoria Land  (Antartica).
  • laboratory experiments.
  • Beside the study of the active volcanism MP carried also volcanological and petrologic studies of volcanic detritus within drilled or gravity cores aimed at paleoenvironmental-paleoclimatic reconstructions.
About the event: 

Textural, compositional and morphological features of pyroclasts generated during explosive eruptions represent the first order source of information for deciphering magma dynamics, eruption and fragmentation mechanisms. The identification of the nature/origin of the products of an explosive eruption is thus the first and most critical step for defining and quantifying the processes that occur before, during and immediately after an eruption within active craters, conduits and sub-volcanic systems (i.e. magma evolution, degassing, ascent, crystallisation, fragmentation and alteration).

Volcanic ash is always present in the products of explosive activity, and it may be easily recovered during the eruption monitoring, from both proximal and distal sites, whatever the intensity of the activity. For this reason, in the recent years, studies on composition, morphology and texture of volcanic ash have been increasingly used to derive indirect information on eruption dynamics, from both past and on-going eruptions. In general, juvenile clasts, show a large variability of external properties and texture, reflecting alternatively the effects of primary processes related to magma storage or ascent, and/or of syn-eruptive modifications occurred during or immediately after their ejection. During the talk a set of characteristics associated with effects of intra-crater modification will be discussed using as example features observed in fine pyroclasts erupted during relevant basaltic eruptions (Stromboli, Etna, Vesuvius, Gaua-Vanuatu) and high temperature experiments. The talk also report results of a combined textural and compositional study carried out on three tephra deposits produced by four violent explosive episodes occurred on December 2015 at Mt. Etna. Ash fractions, which preserve the magma properties unmodified by post- emplacement processes, were used to identify processes occurring in the conduit during a single paroxysm and to understand how they evolve throughout the eruptive period.