Insights from an eruption simulator may help predict future volcanic behavior.
Nearly 2,000 years ago in southern Italy, Mount Vesuvius erupted. An avalanche of ash, rock, and toxic gas rushed down the sides of the mountain, burying the bustling town of Pompeii.
Volcanic flows (aka pyroclastic flows), like the one that famously killed thousands of Pompeii citizens, are responsible for 50 percent of volcano-related fatalities and put half a billion lives at risk worldwide, according to a press release.
But what goes on inside of these deadly flows has been something of a mystery to scientists — measuring their internal dynamics is a major challenge due to their extreme heat and force.
"We decided that if they could not see inside one of these flows, then maybe we could replicate one," says Gert Lube, from Massey University’s Institute of Agriculture and Environment.
The research team used an eruption simulator, which dropped ash and pumice down a channel, along with high-speed cameras and sensors to conduct experiments on the natural behavior of volcanic flows.
Writing in the journal Nature Geoscience, the researchers discovered three distinct currents within the volcanic avalanche — a non-turbulent underflow that hugs the ground, a turbulent hot ash plume above it, and a previously unrecognized middle zone of intermediate turbulence, where the first two currents meet.
"Inside this middle zone, the gas-particle mixture behaved fundamentally different from the turbulent suspension cloud above and the particle-rich avalanche of pumice below,” says Lube.
The patterns formed by particles in this middle zone appear to control how the internal structure of the entire avalanche evolves over the course of a volcanic event, and ultimately, how much damage it could cause, the authors write.
"This opens a new path towards reliable predictions of their motion, and will be particularly topical for hazard scientists and decision makers, because they will lead to major revisions of volcanic hazard forecasts and ultimately more effective measures for keeping people safe," says Dr Lube.
Watch the study authors describe their research in this video: