Unrest at dormant Uturuncu volcano driven by gas and fluid movement, not magma
A new study published in PNAS provides the most detailed view to date of the dormant Uturuncu volcano in southwestern Bolivia, revealing that its long-standing ground deformation and seismic unrest are driven by the movement of hot fluids and gases, not by magma ascent. Researchers conclude there is no immediate eruption risk, but confirm that a deep magmatic system remains active beneath the surface.
Satellite image of Uturuncu volcano, Bolivia on April 19, 2025. Credit: CopernicusEU/Sentinel-2, The Watchers
- After conducting seismology and rock analysis, the study has identified a likely source of the activity: molten rock releasing gas that pushes against Uturuncu’s upper crust.
- The combination of techniques used in the study presents a new way to capture a three-dimensional, CAT scan-like image of subsurface volcanic activity that could help predict eruptions and also potentially identify the location of highly sought-after mineral deposits.
A study published on April 28, 2025, by the University of Oxford, the University of Science and Technology of China, and Cornell University analyzed the subsurface activity of Bolivia’s dormant Uturuncu volcano, which last erupted approximately 250 000 years ago. Using data from more than 1 700 local earthquakes, the researchers mapped the volcano’s internal structure and identified fluid and gas migration as the cause of its current unrest.
Uturuncu is a 6 008 m (19 700 feet) high andesitic-dacitic stratovolcano located in southwestern Bolivia, southeast of the town of Quetena (population 1 200). It is the highest peak in the region and part of the Altiplano-Puna Volcanic Complex (APVC), one of the most geophysically active zones in the Central Andes.
Its edifice is primarily composed of lava flows with no observed pyroclastic deposits. Although some lava flows appear relatively youthful and retain well-preserved flow features, recent field investigations found signs of glaciation on summit flows. Earlier fieldwork by Kussmaul et al. (1977) suggested the presence of postglacial lava flows, but later satellite image analyses by de Silva and Francis (1991) did not confirm evidence of activity following the last glacial period.
Despite the lack of confirmed Holocene eruptions, Uturuncu shows persistent geothermal activity, including two active fumarolic fields near the summit emitting sulfur-rich gases, a sign of underlying heat and volatile release. Large-scale ground deformation, first detected in May 1992 using satellite radar interferometry (Pritchard and Simons, 2002), has been interpreted as a signal of pressure changes at depth, possibly linked to fluid or magma movement.
Between 2009 and 2010, local seismic swarms were recorded (Jay et al., 2012), further suggesting the existence of an active magmatic-hydrothermal system beneath the volcano.
The most recent study combined seismology with petrophysical analysis to examine rock properties and fluid interactions.
Researchers used high-resolution isotropic and anisotropic seismic velocity structures to image the upper crust. This approach provided a three-dimensional view of the volcanic system.
The analysis identified a shallow gas accumulation zone beneath Uturuncu’s crater, explaining its “zombie” activity. Despite earthquakes and gas plumes, the study found no immediate eruption risk. The unrest is attributed to liquid and gas movements, not magma ascent.
Previous studies detailed Uturuncu’s deformation, with uplift rates up to 1 cm (0.4 inches) per year. The new research clarifies that these changes result from fluid dynamics in the hydrothermal system. This system facilitates the upward migration of fluids from the deep magma body.
The research team applied rock physics modeling to understand how fluids interact with the volcanic structure. Their findings suggest that the methods used could apply to other volcanic systems. This could improve hazard assessments for over 1 400 potentially active volcanoes worldwide.
Uturuncu is part of the Central Volcanic Zone (CVZ) of the Andes, a tectonically active belt that extends through southern Peru, western Bolivia, northern Chile, and northwestern Argentina.
Although the country has fewer historically active volcanoes than its neighbors, it hosts several large volcanic complexes with evidence of Holocene activity, including Cerro Nuevo Mundo, Cerro Chascon-Runtu Jarita, and the potentially active Cerro Luxsar and Irruputuncu near the Chilean border.
While no major explosive eruptions have been recorded in Bolivia during the historical period, deposits from large past events are preserved across the Altiplano, particularly within the Altiplano-Puna Volcanic Complex.
This complex has produced some of the largest ignimbrite-forming eruptions in the last 10 million years. Ignimbrites are the result of violent eruptions that release hot, ground-hugging flows of ash and gas, capable of blanketing vast areas in volcanic rock.
These eruptions shaped much of the region’s current volcanic topography and buried older landscapes under thick volcanic deposits.
References:
1 Anatomy of the magmatic–hydrothermal system beneath Uturuncu volcano, Bolivia, by joint seismological and petrophysical analysis – Ying Liu, John Michael Kendall, Haijiang Zhang, et al. – PNAS – April 28, 2025 – https://doi.org/10.1073/pnas.2420996122
2 New study reveals the anatomy of Uturuncu, the “zombie” volcano – University of Oxford – April 25, 2025
3 Uturuncu geological summary – GVP – Accessed May 6, 2025
I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.
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