Dan Rasmussen and Terry Plank collect samples of volcanic ash

Dan Rasmussen, Peter Buck Fellow at the Smithsonian’s National Museum of Natural History, and Terry Plank, volcanologist at Columbia University’s Lamont-Doherty Earth Observatory, collect samples of volcanic ash from a narrow ravine created by a small stream on the flank of Cleveland Volcano in 2016. Layers on the ravine wall are the products of Cleveland’s individual eruptions. The layers are brown because they are breaking down to form dirt. Still, with enough effort, scientists can find some fresh volcanic material in these layers. The layers must be sampled individually, which is a tricky process. First, a flat surface at the interface between two layers is carved out; then, the layer that is exposed is scraped into a sample collection bag, exposing the next layer down and enabling its collection. These samples helped researchers to understand the water contents of Cleveland’s magmas.

A new study, published today, March 10, in the journal Science, finds that, for the world’s most common type of volcano, magma with higher water content tends to be stored deeper in the Earth’s crust. The finding identifies what some scientists expect is the most important factor controlling the depth at which magma is stored and may bring experts one step closer to accurately forecasting volcanic eruptions.

SI-98-2022