Schematic drawing of a volcanic system, with magma chamber and conduit, whose magma rises to the surface forming a cone. During its history, a volcano can alternate periods of open conduit, characterized by almost continuous activity, and periods of quiescence with no eruptive activity and obstructed conduit. Then, the activity can resume with a transition period necessary for new magma to rise, fracture the rocks and create (new) passageways. This dynamics of the ascent of a melt more or less rich in gas, magma, until it comes out, generates innumerable physical and chemical processes both in the earth's crust and on the surface.
The thematic area includes the study of magma dynamics within the volcanic system; analysis of the rising process of magma to the surface and of the interactions between magma, wall rock and hydrothermal system; monitoring of geophysical and geochemical signals associated with magma movements and ascents and analysis of their evolution; development of conceptual, analogical, statistical and theoretical-computational models capable of describing the processes that control the ascent of magmas and their relationship with the signals recorded on the surface.
Schematic drawing illustrating the range of processes that can influence the eruptive style of a volcanic apparatus from the magma reservoir to the surface, before or during volcanic eruptions. Inset a) shows how fragmentation is a function of magma viscosity and strain rate: high strain rates (i.e. high decompression rates) favor brittle fragmentation when passing the glass transition for a given viscosity. With a slow strain rate, magma generally behaves like a liquid. Figure from Gonnermann and Manga, 2003, modified. Inset b) shows the cycle of vesicularity and permeability variation of the outgassing magma - from nucleation, to vesicle coalescence and densification - obtained from permeability and porosity data (in Rust and Cashman, 2004).