New view on erupting volcanoes

Researchers from the University of Illinois, USA, suggest in Nature this week that ‘volcanic mesocyclones’ cause large volcanic plumes — umbrella-shaped columns of hot gases and dust — to behave in a similar way to tornadic thunderstorms.

Pinaki Chakraborty and colleagues analyzed satellite images from six recent large volcanic eruptions — including Mount Pinatubo, Philippines (1991) and Mount Chaitén, Chile (2008). Based on their findings, they believe that waterspouts and lightning sheaths, the meteorological phenomena often observed with massive eruptions, stem from a mesocyclone within the eruption column. The mesocyclone, induced by the updraught of the rising column, causes the entire plume to rotate around its axis, which destabilizes the plume’s umbrella such that it develops an asymmetric lobe-shape when viewed from above.

Until now, scientists were unclear about the forces leading to these meteorological events. In classical eruption models, the plume is assumed to remain symmetric around the axis and not rotate.

This new model provides a unified explanation for the meteorological events associated with strong volcanic eruptions. The researchers hope that concept of a volcanic mesocyclone will enable better forecasts that will alleviate the impacts of volcanic eruptions.