A Zombie Volcano Hasn’t Erupted in 250,000 Years—But Scientists Say It’s Still Alive

Although dormant volcanoes are usually quiet, “zombie volcanoes” like Bolivia’s Uturuncu display a surviving amount of activity for a volcano that hasn’t erupted in 250,000 years.
A new study uses seismic topography, combined with other data sets including rock composition, to create a 3D map of the magmatic and hydrothermal plumbing beneath Uturuncu.
The study shows that the Altiplano-Puna Magma Body, the largest in the world, is feeding hot fluids and gasses toward the surface and trapping CO2 and steam under the summit.

Although not a living, breathing thing like you and me, volcanoes experience their own “life cycles.” Filled with veins of magma and toxic gas rather than blood and plasma, these rumbling geologic formations first experience a calamitous active phase, a more sleepy dormant phase, until eventually going extinct.

Although technically not dead, dormant volcanoes usually show little activity unless they’re on the inevitable road to eruption. In a way, these volcanoes exist in a liminal space between active and extinct. However, some volcanoes defy this easy categorization, and chief among them is the long-dormant Uturuncu volcano in Bolivia. Meaning “jaguar” in the indigenous language Quechua, Uturuncu hasn’t erupted for 250,000 years—give or take 5,000 years or so.

However, that hasn’t stopped this volcano from showcasing extensive gas and earthquake activity, inspiring some toward the label of a “zombie volcano.” Now, a new study from scientists at the University of Science and Technology of China (USTC), Oxford University, and Cornell University have unraveled the mystery of Uturuncu’s undead activity. The results of the study were published this week in the journal Proceedings of the National Academy of Sciences (PNAS).

“When people look at volcanoes, they’re like, ‘Oh, if it’s not going to erupt, we’re not interested in it,’” Cornell University’s Matthew Pritchard, a co-author of the study, said in a press statement. “But actually volcanoes that look dead on the surface are not dead underneath. There are still processes going on. And the processes in Uturuncu are particularly interesting because they’re telling us about the liquids and the gasses that are moving through there that might become, or maybe even today are, a reservoir of minerals that could be useful for technology.”

Shaped sort of like a sombrero—with the volcano jutting upwards while the area surrounding it sinks below—Uturuncu rests on the largest magma body in the Earth’s crust in what’s known as the Altiplano-Puna Volcanic Complex. Scientists know that a hydrothermal system connects this body to the surface but has no idea how the internal fluid mechanics of that system work. To get a clearer picture, the research team used seismic tomography, which uses seismic waves from 1,700 earthquake events. Because these waves interact differently with varying materials in the Earth, scientists were able to construct a 3D model of Uturuncu’s interior. This model was then combined with other data, including rock composition, for an even higher-resolution snapshot of Uturuncu’s magmatic and hydrothermal plumbing.

What the scientists discovered is that the Altiplano-Puna Magma Body is likely sending gasses through a narrow pipe, which causes liquids and gasses to accumulate below the volcano’s crater and is what likely forms Uturuncu’s sombrero-like shape. Because this is caused by liquids and gasses, and not magma, an impending eruption is low, a sigh of relief for locals who live near the volcano. However, studying the internal layout of volcanoes like Uturuncu provides more valuable information than just its explosive probability.

“Fluids are flowing through molten rock and they pick up some minerals on their way, and then they take them somewhere and deposit them,” Pritchard said in a press statement, stating how volcanoes can be breeding grounds for important minerals. “Even though we’re not really worried about this particular volcano erupting in the next few years, we can sort of see in real time the processes of this happening. Clearly there is activity underground that may be even, at some point, economically useful.”

Uturuncu also isn’t the only “zombie volcano” of its kind, as many similar formations around the world that haven’t erupted for thousands of years though still show a surprising amount of activity. Understanding these signs of activity could help scientists sort through which volcanoes are an impending threat and which are simply blowing smoke.

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