Abstract

Since the 80’s, the monitoring of silicic volcanoes using geophysical techniques has largely been developed around the world. This has allowed important advances on our understanding of magmatic and volcanic processes.
First, the concept of magma chamber has radically changed. Indeed, geophysical surveys do not find large liquid magma bodies below active volcanoes, but only large, diffuse, partial melt zones. Magma chambers are now described as large mush zones located at different levels in the crust and constructed by accumulation of small magma batches over hundreds of millions of years. The two-phase dynamics of a crystal and magma mixture thus controls melt extraction during periods of unrest.
Second, the activity of silicic volcanoes has appeared cyclic and marked by different periods of cyclicity going from tens of years to the second. Some of them are clearly linked to the very different physical properties and behaviors of the different phases present in magmatic systems: crystal, melt and gas.
In the end, at arc-volcanoes, melts extracted from the mantle face a complex and vertically stratified filter: the crust. Understanding the dynamics of a three-phase mixture in a vertically stratified environment is thus crucial for the assessment of eruptive risk, in particular to describe the transfer function characteristic of this crustal filter.