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Volcanic eruptions spew fine ash, sulfur, and crystal-poor magma into the atmosphere. New research suggests how light vapor bubbles migrating and accumulating in parts of shallow volcanic chambers contribute to the effects.
Volcanic chambers are a maze of crystal-rich and crystal-poor regions, especially where magma stalls and builds before eruption. The researchers used lab experiments and computer models to focus on how bubbles move to and through these shallow reservoirs, which are three to five miles below the surface.
“We know that bubbles control the style and power of eruptions, but we don’t fully understand how they behave,” said Christian Huber, an assistant professor in Georgia Tech’s School of Earth and Atmospheric Sciences. “It’s probably like opening a soda and watching the bubbles race to the top of the bottle.”
Huber and colleagues from Eidgenössische Technische Hochschule Zurich (ETH) believe these bubbles maneuver their way through crystal-filled magma until they settle in these open-spaced reservoirs — areas without many crystals — and build up the necessary energy for an impending eruption.
The team’s experiments indicate that bubbles squeeze through the narrow openings to create finger-like paths. These long paths allow the bubbles to merge and form connected pathways that transport low-density vapor efficiently through the crystal-rich parts of magma chambers.
“Once they reach the end of this crystal-rich area and get more space, the water vapor fingers transform back into their usual, spherical bubble shape,” said Andrea Parmigiani, who led the study during his postdoctoral work at Georgia Tech and ETH. “Once vapor forms these bubbles, the ascent of the light vapor bubbles is slow and bubbles accumulate.”
The findings were reported in the journal Nature. — Jason Maderer