‘Singing’ lava lakes could help predict when volcanoes will erupt

In 2007, lava began to build up in one of the craters of Hawaii’s Kilauea volcano, a gentle eruption that would culminate more than a decade later in a spectacular display of spitting ash and massive lava flows. Until this latest explosion, the lava lake was a tourist sight, a quiet surface that hid churning magma deeper within the volcano. Now researchers have found a new way to identify key signs of Kilauea’s eruptive potential by listening to the vibrations of these lava lakes. Eventually, they hope to use these lava “songs” to predict when a volcano will start and stop erupting.

“It’s great that they’ve found this other way to understand what’s going on at Kilauea,” says Philippe Jousset, a geophysicist at the German Geoscience Research Center who was not involved in the study. “[This] can help us understand… the most dramatic changes in volcano behavior.

When chunks of rock from the volcano’s crater rim fall into the lake, the lapping lava generates distinct seismic waves that last for tens of seconds. For years, researchers have suspected these long seismic signals may contain information about the magma below– in the same way that the noise you get from tapping a spoon on a glass of water can reveal the amount of liquid present. The pitch and duration of this sound would change more if you dissolved gases in water or replaced water with milk. Likewise, scientists believed that the resonant waves of the lava lake could encode details about its magma reserve.

After Kilauea’s 10-year eruption ended, scientists had “this incredible record” to work with, says Leif Karlstrom, a volcanologist at the University of Oregon and the study’s lead author. Him and his then doctorate. Student Josh Crozier has collected data on thousands of events from seismic sensors, GPS stations and lake level observations. Then they built a computer model that showed what happened when rockfall disrupted the lava lake and produced the signals. By adjusting different variables in the simulation, such as temperature and gas bubble content, they were able to determine which combination of magma properties best matched the real data.

A compilation of very long-period seismic recordings used to study Kilauea’s lava lake from 2015 to 2018, sped up about 8,000 times so it can be heard by humans. The subtle changes in tone reflect variations in magma properties, such as temperature and bubble content.Leif Karlstrom

The model unveiled magma temperature was strongly linked to the duration of seismic signals, they report today in Scientists progress. The signals also gave clues to the amount and composition of bubbles embedded in the magma — information that is usually only available after an eruption, Karlstrom says. Gas content is an important variable to track, he adds, because eruptions are caused by “bubbles in the magma that want to come out.” Changes in lava song have mirrored individual explosions throughout Kilauea’s long episode, including the big one in 2018. The hope is that one day these volcanic tunes will help scientists monitor magma and predict eruptions, although accurate predictions require models with more detailed physics. . His team works to assemble different types of data and integrate machine learning algorithms to improve the recognition of eruptive events.

Although Kilauea provides an excellent laboratory for predicting eruptions, not all volcanoes have lava lakes that produce such long, clear seismic signals, Jousset says. Still, the new work, with its many years of observations, opens “a new perspective” on how volcanic eruptions evolve, Karlstrom says.

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