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Pre- and syn-eruptive conditions of the 1631 and 1944 eruptions of Vesuvius volcano: implications for eruptive style transition

Rebecca Cavallera1 , Carlo Pelullo2, Domenico Sparice2, Ilenia Arienzo2, Michael Robert Carroll1, Fabio Arzilli1

  • Affiliations:  1Università di Camerino, Scuola di Scienze e Tecnologie, sezione Geologia, Camerino, Italy, 2Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 212

  • Programme No: 3.2.35

  • Theme 3 > Session 2

Abstract

Intermediate to evolved alkaline magmas have relatively low viscosities compared to similar calc-alkaline magmas. Despite this, they can give rise to a wide range of eruptive styles, from effusive lava flows to highly explosive, catastrophic eruptions. The processes and the pre- and syn-eruptive conditions driving the transitions between the different eruptive styles remain poorly understood and investigated in alkaline volcanic systems. This study aims to identify the leading causes of these transitions at Mt. Vesuvius, selecting as case studies the 1631 and 1944 eruptions. During the 1631 eruption, the intensity gradually decreased, shifting from a Plinian to Vulcanian phase, whereas the 1944 eruption was characterized by increasing intensity, producing lava flows, followed by vigorous lava fountains and finally a Vulcanian phase. The eruptive style transitions have been investigated through detailed textural, chemical analyses and modelling. The preliminary results indicate that temperature, pressure and crystal content variations could have been parameters controlling the eruptive style during the two eruptions: during the 1631 eruption, the Plinian phase erupted at 900-950 °C, whereas the Vulcanian phases erupted at 1000-1050°C, starting at a pressure of 100 MPa. The Plinian phase shows a lower crystal content than the Vulcanian phase. For the 1944 eruption, pre-eruptive temperatures are relatively consistent from the initial effusive phase to the last Vulcanian phase, ranging from 1030 °C to 1090°C. These products recorded different pressures: up to 300 MPa in melt inclusions hosted in clinopyroxenes, 50 MPa in melt inclusions hosted in leucite. These differences are currently being investigated.