Syneruptive textural mingling as trigger of a Subplinian basaltic monogenetic eruption
Lisa Corrotti1 , Lucia Gurioli1, Etienne Médard1, Karoline Brückel1, Carole Berthod2
Affiliations: 1Laboratoire Magmas et Volcans, Université Clermont Auvergne, Clermont Ferrand, France; 2Observatoire Volcanologique et Sismologique de Guadeloupe, Institut de Physique du Globe de Paris, Paris, France
Presentation type: Poster
Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 97
Programme No: 3.16.24
Abstract
Scoria cones are commonly associated with monogenetic, weakly-explosive eruptions emitting small volumes of magma. However, recent research has shown that these eruptions can be violent as was the case at La Vache and Lassolas. These two monogenetic cones located in the south of the Chaîne des Puys (France) were formed by a complex trachybasaltic eruption 8600 years ago. This eruption consisted of 5 phases: (i) an opening phase, (ii) a Subplinian phase, (iii) a violent Strombolian, main cone forming phase with simultaneous emission of a lava flow, (iv) a last Strombolian activity marked by the arrival of a fresh, gas-rich magma, (v) and a final phase purely effusive. This study combines textural and petrological analysis of the explosive products throughout the entire eruptive sequence and highlights four main results. The feeding system was composed of two reservoirs located at 30 km (near the MOHO) and 12 km, the lowest one being injected by pulses of basaltic magma. A partially degassed and crystallized magma batch close to the surface acted as a plug for the ascent of fresh magma. The explosivity of the eruption was caused by the overpressure in the system when fresh magma met this degassed magma body. Preliminary estimates of the time elapsed between the first magma recharge event and the eruption varies from a few hours to a few days. If such durations prove to be robust, then this type of eruption represents a non-negligible hazard for the surrounding populations.