Abstractions

摘要

The hot gases and dust that erupt from a volcano form a plume with a vertical column topped by a horizontal cloud, or umbrella. The umbrella is known to change shape over time from a circle to a wavy, tabular form, but no one knew why. Postdoc Pinaki Chakraborty of the University of Illinois at Urbana-Champaign and his colleagues set out to learn what caused the change. Using satellite images of recent eruptions and an obscure 1811 paper that describes a volcanic plume erupting from the sea, the team concludes that the volcanic plume actually spins about its axis, a phenomenon they have dubbed a volcanic mesocyclone. This rotation model explains the umbrella's changed shape and unravels other mysteries, including why lightning and waterspouts or dust devils usually accompany volcanic eruptions (see page 497). Chakraborty tells Nature more.