The study connects the depth at which magma is stored to water, which is significant because water largely initiates and fuels eruptions. When magma is stored beneath a volcano, a sudden decrease in pressure can cause gas bubbles to form, leading to the magma rising and jetting out of the volcano. More water content in magma means more gas bubbles and potentially a more violent eruption.
Rasmussen’s research began in 2015 while completing his doctorate at Columbia University’s Lamont-Doherty Earth Observatory. He went into the field to collect volcanic material from eight volcanoes located in the rugged and remote Aleutian Islands, focusing on a particular geological setting when selecting volcanoes for this study: so-called arc volcanoes that occur at the intersection of two converging tectonic plates.
Volcanic Ash and Olivine Crystals
Volcanic ash was the primary target of the expedition because it can contain green crystals made of olivine, each one with a thickness of a plastic ID card. Underground, these olivine crystals sometimes trap tiny bits of magma when they form. After an eruption sends these special olivine crystals to Earth’s surface, the magma inside them cools and becomes glass. By analyzing the chemical composition of these minuscule pieces of cooled magma from the inside of a volcano, the researchers were able to estimate the magma’s water content.