Lab experiment reveals potential volcano trigger

The Guardian : An international team of researchers led by geologist Sandy Cruden of Monash University in Melbourne, Australia, has identified a new mechanism by which ascending magma could trigger volcanic eruptions. The team made the discovery by simulating Earth’s crust with a tank filled with two layers of pigskin gelatin of differing viscosity. Colored water was injected from below to mimic upwelling magma. When passing through the lower-viscosity layer at the bottom, the water flowed in a vertical column. But when it reached the high-viscosity layer, it spread horizontally to form what geologists call a sill. By suffusing the gelatin with fluorescent particles and illuminating it with a laser, the researchers found that the horizontal spreading lowered the pressure in the upper layer, causing the layer to sag. Some volcanic eruptions occur when a reduction in pressure causes one side of a volcano to collapse. Sill formation could be the trigger.