Bolivia’s long-dormant ‘zombie’ volcano coming back to life after 250,000 years

by Mrigakshi Dixit
April 28, 2025

High in the Central Andes, a geological enigma lies dormant.

Uturuncu volcano in Bolivia hasn't erupted in over 250,000 years. It is also known as a "zombie" volcano because it still exhibits unsettling signs of life, like earthquakes and gas emissions.

Previously, the ongoing activity of this seemingly inactive volcano was puzzling, leading scientists to believe the explanation lay in the subsurface movement of magma and gases.

An international collaboration of scientists from China, the UK, and the USA has delved deep into Uturuncu's inner workings.

The new study combines the power of seismology, sophisticated physics models, and detailed analysis of the volcano's rock composition.

“Our results show how linked geophysical and geological methods can be used to better understand volcanoes, and the hazards and potential resources they present,” said Professor Mike Kendall, co-author from the Department of Earth Sciences, University of Oxford.

Cerro Uturuncu, right, and Cerro San Antonio, left, volcanoes above the small town of Quetena Chico on the Bolivian Altiplano. Photo Credit: Jon Blundy, University of Oxford.

Use of an advanced seismic imaging technique

The volcano's unrest results in a distinctive "sombrero"-shaped ground deformation. The land above the volcanic system bulges upwards, while the areas around it sink.

Understanding the potential for a real eruption is paramount for the communities living nearby. The stakes are high, with the threat of widespread devastation and loss of life looming.

By meticulously analyzing signals from over 1,700 earthquake events, the team has created high-resolution images of the shallow crust beneath Uturuncu. This technique is known as seismic tomography.

Seismic waves travel at varying speeds through different materials, allowing scientists to map the underground landscape precisely.

Combining this with an understanding of the physical properties of the rocks, the researchers have pieced together a clearer picture of Uturuncu.

Reason behind volcano's zombie-like behavior

The findings point to an explanation for Uturuncu's zombie-like behavior.

The unrest isn't necessarily a prelude to a major eruption. Instead, it appears to be driven by the movement of geothermally heated liquids and gases deposited in reservoirs just beneath the volcano's crater.

The research team concludes that the movement and accumulation of liquids and gases beneath the crater are the most probable cause of the ground deformation observed at the center of the volcanic system.

The research suggests a low likelihood of an imminent eruption.

"Understanding the anatomy of the Uturuncu volcanic system was only possible thanks to the expertise within the research team. This enabled us to combine various advanced geophysical imaging tools with modelling of the rock properties and their interactions with fluids," said Professor Haijiang Zhang, the co-author from the School of Earth and Space Sciences, University of Science and Technology of China, in the press release.

The team suggests that the study techniques be valuable for investigating over 1400 potentially active volcanoes and the many other seemingly inactive, zombie-like volcanoes.

The study involved researchers from the University of Science and Technology of China, the University of Oxford, and Cornell University.

The findings were published in the journal PNAS.