Hunting for clues about pyroclastic surges in lonely desert landscapes

Thousands of years ago, at different points in time, clouds of ash, rock and hot gas rushed across the Mojave and Sonoran deserts as two volcanoes erupted.

These destructive events are long over. But their history is written in the lonely landscapes they ravaged. Volcanic dunes and other deposits hold debris from the ancient eruptions, as do craters marking the sites of the blasts — Ubehebe in Death Valley in the Mojave Desert in the U.S., and El Elegante in the Gran Desierto de Altar in the Sonoran Desert in Mexico.

In a $607,000 study funded by the National Science Foundation, researchers from UB, Arizona State University (ASU) and Boise State University are taking a close look at these two locations, with the hope of illuminating how violent currents of ash, rock and gas — called pyroclastic surges — move across complex terrain.

­“I grew up on the side of a supervolcano, if you want to use the term that you see on the Discovery Channel,” says Greg Valentine, professor of geology, College of Arts and Sciences, who spent most of his youth in New Mexico. “So even as a kid, I was walking across deposits from pyroclastic surges and flows with my dog. I loved wandering across the landscape and just noticing all the details, and the whole idea of volcanic eruptions was really cool — how the eruptions work, and how that’s recorded in the landscape.

“What I love to do is link volcanic deposits to the dynamics: What happened during the eruption? The deposits are just sitting there, but they record some very complicated processes,” Valentine says. “What I try to do is work backwards: Based on what we see in the deposits, what were the volcanic processes that occurred? It’s a weird hobby.”

Valentine is leading fieldwork at Ubehebe with a team that includes PhD student Meredith Cole and MS students Patrick Bobbitt, Brandon Keim and Anastasia Rashchupkina, all in UB’s geology department. The scientists have traveled to the crater. There, beneath a huge open sky, they study surrounding volcanic deposits, measuring the size of ash particles in layers of debris, for example, or documenting the shape and slope of volcanic dunes.

Amanda Clarke, professor in the ASU School of Earth and Space Exploration, along with Brittany Brand, associate professor of geoscience at Boise State, are directing fieldwork at El Elegante, as well as lab experiments that use a special tank called a flume to test how particles from fast-flowing currents may collect in dunes. The group from ASU includes PhD students Saira Hamid and Elisheva Sherman, and MS student Rupa Ragavan.

Using data from fieldwork and experiments, Mattia de’ Michieli Vitturi, UB assistant professor of geology, will develop computational models that simulate how pyroclastic surges move across complex terrain.

“We want to understand the dynamics and the energy of this kind of flow, which can potentially help to quantify the impact they could have on buildings and infrastructure,” de’ Michieli Vitturi says. “This will improve our knowledge for hazard assessments. Our project will also bring new capability into volcanic flow modeling. In fact, this modeling capability will be applicable also to more concentrated pyroclastic currents, whose behavior is similar to that of snow avalanches.”

“Volcanoes can cause hazards and significant damage to nearby settlements. In order to model the probabilistic behavior of future eruptions, volcanologists study volcanic processes and deposits,” says Rashchupkina, who traveled to Ubehebe to help collect samples of volcanic deposits. “At Ubehebe, we were studying volcanic deposits in different locations that will help us understand features and conditions of the eruption. I am grateful for the opportunity to see how scientists create science right in the field, and to make a contribution.”