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Abstract

The rhyodacitic 172 ka Lower Pumice 2 (LP2) eruption terminated the first magmatic cycle at Santorini (Greece), producing a proximal −1, and the development of a 36 km high Plinian eruption column (LP2-A2, A3). The progressive increase in maximum vesicle number density (NVF) in rhyodacitic pumice, from 3.2 × 109 cm−3 in the basal fall unit of LP2-A2-1 to 9.2 × 109 cm−3 in LP2-A3, translates to an increase in magma decompression rate from 18 to 29 MPa s−1 over the course of the initial Plinian phase. This is interpreted to be a consequence of progressive vent widening and a deepening of the fragmentation surface. Such interpretations are supported by the increase in lithic clast abundance vertically through LP2-A, and the occurrence of basement-derived (deep) lithic components in LP2-A3. The increasing lithic clast content and the inability to effectively entrain air into the eruption column, due to vent widening, resulted in column collapse and the development of pyroclastic density currents (PDCs; LP2-B). A major vent excavation event or the opening of new vents, possibly associated with incipient caldera collapse, facilitated the ingress of water into the magmatic system, the development of widespread PDCs and the deposition of a <20 m thick massive phreatomagmatic tuff (LP2-C). The eruption cumulated in catastrophic caldera collapse, the enlargement of a pre-existing flooded caldera and the discharge of lithic-rich PDCs, depositing proximal <9 m thick lithic lag breccias (LP2-D).

Item Type:	Article
Authors/Creators:	Simmons, JM and Cas, RAF and Druitt, TH and Carey, RJ
Keywords:	volcano, eruption, magma, Lower Pumice 2, Santorini, precursor, Plinian, caldera, magma decompression
Journal or Publication Title:	Journal of Volcanology and Geothermal Research
Publisher:	Elsevier Science Bv
ISSN:	0377-0273
DOI / ID Number:	https://doi.org/10.1016/j.jvolgeores.2017.05.034
Copyright Information:	Copyright 2017 Elsevier B.V.
Related URLs:	Google Scholar: Carey, RJ UTAS Profile: Carey, RJ
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