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Satellite images reveal magma chambers beneath Bali's Agung volcano

"Because Sentinel-1 satellite radar images are freely available all around the world, we can actually use the same approach to analyze volcanic unrest on other active stratovolcanoes," geophysicist Fabien Albino said.

By
Brooks Hays
One of NASA's satellites imaged Agung shortly after it began erupting in 2017. Photo by NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team
One of NASA's satellites imaged Agung shortly after it began erupting in 2017. Photo by NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team

Feb. 18 (UPI) -- Scientists have developed an improved technique for mapping the magmatic plumbing systems beneath volcanoes using only satellite imagery.

To track the movement of magma beneath Bali's deadly Agung volcano, geologists relied on images collected by the European Space Agency's Sentinel-1 satellites. Their analysis showed the plumbing systems of Agung and the nearby Batur volcano are likely connected.

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In 1963, Agung erupted violently, killing nearly 2,000 people. In 2017, Agung erupted again, after 50 years of dormancy. The most recent eruption was proceeded by hundreds of small earthquakes. Fearing another violent eruption was eminent, authorities evacuated 100,000 people in the wake of the local tremors.

Agung has been slowly erupting, on and off, over the last year-and-a-half. As Agung rumbled, scientists around the world worked to understand Agung's re-awakening.

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One group of researchers, led by geophysicists at the University of Bristol, realized satellite images could reveal the volcanic ground deformation that occurred prior to the 2017 eruption.

"The surface deformation on volcanoes are usually related to the storage or the propagation of magma below the volcanoes," Bristol geophysicist Fabien Albino told UPI in an email. "By the modeling of the ground deformation signals, we can provide constraints on the geometry and the depth of the magmatic system."

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The model developed by Albino and his colleagues showed magma moved horizontally, as well as vertically, in the lead up to the 2017 eruption, and that the maximum displacement was concentrated some three miles from Agung's summit, not far from Batur.

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"Because the plumbing system is not centered on Agung but located between the two volcanoes, we suggest that these two volcanoes could be connected, which might explain the simultaneous eruptions in 1963," Albino said.

In addition to helping scientists understand why Agung and Batur erupted simultaneously more than a half-century ago, the latest research -- detailed in the journal Nature Communications -- could aid future forecasting models and help keep the people living next to Agung and Batur safe.

"Statistically, ground deformation is a precursor of volcanic eruptions," Albino said. "So, the detection and the interpretation of ground deformation signals on active volcanoes such as Agung is crucial to improving our understanding of the dynamics of magmatic systems -- and is valuable information for eruption forecasting and risk assessment."

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According to Albino, the same techniques he and his colleagues used to study Agung can be used to understand volcanic systems all over the world.

"Because Sentinel-1 satellite radar images are freely available all around the world, we can actually use the same approach to analyze volcanic unrest on other active stratovolcanoes and compare to the case of Agung," he said. "For future studies, we would like to investigate if other pairs of volcanoes with connected magmatic systems."

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