Forecasting magma movement through the crust

magma
The Valle del Bove at the flank of the Etna volcanoe on Sicily (photo: E. Rivalta, GFZ).

Assessing the hazard of volcanic eruptions requires knowledge on where exactly eruptive fissure will be located. Scientists from the Institut des Sciences de la Terre, France, and the GFZ have developed a method to forecast how fast a volcanic dike propagates through the crust and in which direction it will grow. Their study, published in the Journal of Geophysical Research: Solid Earth, was now distinguished as a “research spotlight” by the news platform EOS of the American Geophysical Union AGU. Like this, EOS honors “the best accepted articles” that were published in an AGU journal.

Some volcanoes erupt through established conduits but many eruptions occur from fissures or vents that open on the volcano flank. This results from the propagation of magma-filled cracks, called “dikes”, that are released from magma chambers at depth. These dikes force their way through the Earth’s crust, eventually opening a new surface fissure. Thus, in order to assess the volcanic hazard, it is necessary to forecast whether a propagating dike will make it to the surface and end in an eruption, and if so, where and when that eruption will occur. In addition, the explosivity of an eruption may depend on the location of the vent, due to interaction of magma with ice or water.

Two alternative modelling approaches were so far developed to simulate magma propagation: The viscous-dominated approach provides the possibility to obtain how fast a dike propagates, but only for those propagating rectilinearly. The fracturing-dominated approach on the other hand provides information on the trajectory of a dike.

The scientists, with the participation of Eleonora Rivalta and Francesco Maccaferri from the GFZ section Physics of Earthquakes and Volcanoes, now integrated the two approaches within their new study. They developed a hybrid method where the “speed” of propagation is calculated with the viscous-dominated approach, and then the fracturing-dominated approach gives information on the direction of the trajectory. This resulted in the first model jointly addressing the trajectory as well as the velocity of a dike and therewith also providing information on the time of eruption. (jz)

Original study: Pinel, V., Carrara, A., Maccaferri, F., Rivalta, E., Corbi, F., 2017. A two-step model for dynamical dike propagation in two dimensions: Application to the July 2001 Etna eruption. Journal of Geophysical Research: Solid Earth 122 (2). DOI: 10.1002/2016JB013630