In the remote reaches of the Central Andes, the dormant yet restless volcano Uturuncu has long puzzled volcanologists. Though its last eruption occurred roughly 250,000 years ago, this so-called “zombie” volcano continues to exhibit signs of subterranean activity that belie its dormant classification. Recent collaborative research involving scientists from China, the United Kingdom, and the United States has shed new light on the enigmatic processes driving Uturuncu’s persistent unrest. By blending seismological data, advanced physical modeling, and comprehensive rock compositional analyses, the team has reconstructed a high-resolution image of the volcano’s underground plumbing system, offering unprecedented insight into its inner workings and effectively quelling fears of an impending eruption.
Uturuncu’s persistent activity is manifested through a distinct geological phenomenon known as the “sombrero” deformation pattern, where the central volcanic edifice is uplifting while the surrounding terrain subsides. This pattern is a clear indicator of complex fluid and gas dynamics occurring beneath the surface, yet until now, the underlying mechanisms remained elusive. The nature of Uturuncu’s unrest has important ramifications for local communities and regional hazard assessment, as any volcanic eruption could potentially threaten lives and infrastructure. Understanding how magma and volcanic gases are mobilized beneath the volcano is therefore critical to evaluating eruption risk and preparing adequate mitigation strategies.
To unravel these processes, the scientific collaboration employed seismic tomography, an imaging method analogous to medical CT scans, which interprets the velocity variations of seismic waves traversing diverse materials. Using data from over 1,700 seismic events recorded beneath Uturuncu, the researchers created a three-dimensional model revealing the complex architecture of magmatic and hydrothermal reservoirs within the shallow crust. This approach allowed them to map zones where liquids and gases accumulate, characterize migration pathways for geothermal fluids, and distinguish between different rock types based on their seismic properties. Their findings demonstrate that the ongoing unrest is predominantly driven by the movement of hydrothermal fluids rather than direct magma intrusion, substantially reducing the likelihood of an imminent volcanic eruption.
The Altiplano-Puna Volcanic Complex (APVC), one of the largest known magmatic bodies in the Earth’s crust, lies beneath Uturuncu and plays a critical role in its subsurface dynamics. Previous research established that Uturuncu is underlain by this extensive molten reservoir, but how fluids permeate from these deep magmatic sources to the surface remained unclear. The new study elucidates that an active hydrothermal system links the magmatic body with the overlying volcanic edifice, facilitating the upward migration of geothermally heated fluids through interconnected conduits. This underground plumbing operates as a dynamic system where fluids and gases accumulate in pressurized reservoirs situated directly below the volcano’s crater, causing the characteristic surface deformation detected at Uturuncu.
By integrating seismic imaging with petrophysical analysis — which examines rock properties and their interaction with fluids — the research team forged a detailed understanding of the volcanic system’s anatomy. This comprehensive approach allowed for the differentiation between fluid-filled fractures, solidified magma, and porous rock formations. Notably, seismic velocities in areas saturated with liquid and gas phases differ significantly from solid rock, enabling the delineation of fluid pathways critical to the system’s pressurization and deformation. Such intricate assessments of the volcanic plumbing provide vital clues about ongoing subsurface processes, highlighting regions where gas accumulation responds to the geological stress regimes influencing the volcano’s behavior.
The use of seismic tomography to image a volcano’s inner structure represents a significant methodological advance in volcanology. Seismic waves, generated naturally by earthquakes or artificially, travel at speeds that depend on the medium’s density, elasticity, and temperature. In regions where fluids or partially molten materials dominate, these waves slow down, creating distinctive pockets of low seismic velocities that act as proxies for subsurface reservoirs. Combining these geophysical signals with models of rock mechanics and fluid dynamics enables researchers to construct a coherent picture of how volcanic systems evolve over time, shedding light on the delicate interplay between magmatism, hydrothermal circulation, and surface deformation.
Central to the study’s success was the international collaboration harnessing diverse expertise, ranging from seismological analysis and geological mapping to advanced computational modeling. Professor Mike Kendall from the University of Oxford emphasized the importance of integrating complementary geophysical and geological methodologies to decipher the complexities of volcanic systems. The multidisciplinary approach allowed researchers to juxtapose empirical seismic data with theoretical rock-fluid interactions, offering a paradigm for studying volcanoes worldwide. This model serves not only to understand Uturuncu’s behavior but also to inform hazard assessments for thousands of other volcanoes exhibiting prolonged unrest without eruptive activity.
The implications of this research extend far beyond Uturuncu. Many volcanoes globally — approximately 1,400 are classified as potentially active, with dozens resembling Uturuncu’s “zombie” behavior — show signs of life despite long periods of dormancy. Co-author Professor Matthew Pritchard from Cornell University highlighted how the methodologies refined in this study could unlock mysteries in other volcanic systems exhibiting delayed or suppressed eruptive activity. The ability to discern fluid migration and reservoir dynamics beneath such volcanoes is vital for refining eruption forecasting models and reducing uncertainty in volcanic hazard predictions, ultimately providing more effective early warning systems for vulnerable populations.
Moreover, understanding the magmatic-hydrothermal systems beneath volcanoes has wider implications for geothermal energy exploration. The detection of heated fluids migrating through the crust can pinpoint potential reservoirs suitable for sustainable geothermal power extraction. This dual scientific and practical insight represents a compelling synergy between volcanology and renewable energy resource management. As geothermal energy gains prominence in global efforts to combat climate change, studies like this exemplify how fundamental earth science can contribute to societal resilience and sustainable development.
In addition to providing clarity on Uturuncu’s current state, the study sets a precedent for the integrated analysis of seismological and petrological data to unravel complex subterranean environments. The combination of high-fidelity seismic tomography with detailed rock property characterization enhances the resolution and interpretative power of volcanic imaging techniques. This approach can be adopted in diverse volcanic settings to distinguish between magmatic activity and hydrothermal processes, two phenomena that have vastly different eruption probabilities and hazard profiles. As a result, volcanologists can better pinpoint signs of magmatic intrusion that may precede eruptions, thereby improving risk mitigation strategies.
Importantly, the research contributes to a broader understanding of the interactions between tectonics, magmatism, and surface processes in the Central Andes, a region characterized by intense geological activity. Uturuncu sits along active crustal faults and deformation zones, where the interplay between deep magma bodies and shallower hydrothermal systems modulates the volcano’s surface expression. By elucidating these interactions, the study not only enhances volcanic hazard assessment but also informs fundamental geodynamic theories regarding crustal deformation and fluid-rock interactions in convergent plate boundary environments.
While the study offers reassuring conclusions about the low risk of an imminent eruption, it simultaneously underscores the need for continuous monitoring and detailed investigations into supposedly inactive volcanoes showing signs of unrest. Volcanic systems are inherently complex and dynamic, with processes unfolding over timescales that often exceed human observation windows. The persistence of deformation and seismicity at Uturuncu challenges static categorizations of volcanic status and compels a reevaluation of how volcanic activity is understood and communicated to the public and policymakers.
Future research building upon this foundational work is poised to expand the capabilities of volcanic imaging and hazard assessment. By deploying denser seismic networks, incorporating complementary geophysical techniques such as magnetotellurics and gravity surveys, and advancing computational modeling, scientists can refine the anatomical maps of volcanoes even further. Such integrated studies will be instrumental in developing predictive models that can anticipate changes in volcanic activity with greater lead times, ultimately safeguarding communities living in volcanic regions worldwide.
In conclusion, the collaborative research on Uturuncu volcano exemplifies the power of cutting-edge seismological imaging combined with petrophysical analysis to demystify the workings of a complex magmatic-hydrothermal system. The findings reveal that the volcano’s unrest stems not from magma forcing its way to the surface, but from the cryptic movement of fluids within interconnected reservoirs beneath the crater. This breakthrough not only alleviates concerns over an imminent eruption but also provides a roadmap for studying and mitigating risks from similarly restless or “zombie” volcanoes erupting unpredictably across the globe.
Subject of Research: Anatomy of magmatic hydrothermal system beneath Uturuncu volcano, Bolivia, via joint seismological and petrophysical analysis
Article Title: Anatomy of the magmatic hydrothermal system beneath Uturuncu volcano, Bolivia, by joint seismological and petrophysical analysis
News Publication Date: 28-Apr-2025
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DOI link to article
Image Credits: Duncan Muir, Cardiff University
Keywords
Volcanoes, Magma, Volcanic eruptions, Scientific collaboration, Rocks, Geology, Geophysics, Seismology, Subsidence, Seismic tomography
