Bursting the bubble: volcanic secrets revealed
The EU's MULTIMO project set out to develop new ways of modelling volcanic activity and thus forecasting its inherent hazard. The Institute of Earth Sciences at the Hebrew University, developed a series of analytical models relating to volcanic events. Specifically, the Institute concentrated on bubble growth in magma and tried to model their formation under different sets of circumstances. The formation of bubbles, as gases go out of solution when magma rises to the surface and the pressure decreases, is characteristic of volcanic eruptions. Researchers initially modelled bubble formation during decompression of magma. Magma decompression occurs during its rise to the surface. The new model presents bubble growth as a function of the diffusive as well as the viscous time scales over the duration of the decompression event. The model provides further details on the state of the erupting magma in terms of gas overpressure, supersaturation and gals volume fraction. Further models were developed to express the bulk viscosity of suspension of gas bubbles in incompressible Newtonian liquid. Decompressing such suspensions results in their expansion. The motion and the pressure affect the bulk viscosity and thus serve to model the overall behaviour. The research team also tried to model fragmented magmatic flows observed during explosive eruptions. This type of magma acts as an elastic substance and not a fluid, thus altering its profile. Preliminary models, describing bubble growth, were developed taking into account the conditions under which magma would take on visco-elastic characteristics. Although often challenging to quantify accurately, bubble growth in magma is an extremely important determinant of volcanic hazard assessment and a fundamental aspect of any volcanic system. The work carried out during the MULTIMO project could signify a new approach towards the accurate prediction of volcanic events and their risks.
