Uturuncu, a prominent peak in Bolivia’s Central Andes, is often referred to as a "zombie volcano" since it has remained dormant for over 250,000 years. Despite its inactivity, the volcano exhibits signs of life, including gas releases and seismic events. Satellite data has revealed significant deformation of a 150-kilometre-wide area near its summit, resembling the shape of a sombrero.
Recent scientific investigations have aimed to determine if these signals indicate a potential resurgence of volcanic activity. Researchers combined satellite imaging with seismic analysis and rock pressure models, leading to enhanced insights into Uturuncu’s internal structure. Their findings were published in the Proceedings of the National Academy of Sciences.
Eruptions primarily occur when magma rises and accumulates in subterranean pockets, leading to explosive releases of pressure. However, the study found that beneath Uturuncu, a vast magma reservoir known as the Altiplano-Puna Magma Body is situated at depths of 10 to 20 kilometres. This reservoir is the largest known active magma body on Earth. The research established that interactions between magma, gases, and hydrothermal fluids—rather than a straightforward accumulation of magma—are responsible for the observed unrest.
The study involved analysing data from over 1,700 seismic events, which produced intricate images of the underground crust. Additionally, researchers monitored electrical and gravitational changes, alongside shifts in rock chemistry, to elucidate the hydrothermal systems at play. They discovered that as the magma heated underground fluids, these gases and liquids moved upward, leading to a gradual surface rise of about one centimetre annually.
According to Dr Mike Kendall, a co-author of the study, the current seismic activity does not indicate an imminent eruption. Instead, it suggests a calming phase where the volcano is primarily venting gases. Kendall emphasised that there is no increasing seismicity or signs of magma movement closer to the surface, essential indicators of potential eruptions.
The findings also contribute to broader volcanology research, as many volcanoes can exhibit activity without being on the brink of eruption. Fuelling ongoing monitoring, the Global Volcanism Program has identified around 50 such "zombie" volcanoes globally. Some display geothermal features indicative of potential energy resources, while others may be cooling down after previous active periods.
The detailed analysis of Uturuncu’s subsurface structure could inform strategies for harnessing geothermal energy and accessing valuable minerals, such as copper and platinum. Geologist Dr Benjamin Andrews highlighted the importance of using multiple research methods to gain a comprehensive understanding of volcanoes, which is crucial for risk assessment related to their activity.
Overall, the study of Uturuncu sheds light on the complexity of undying volcanoes and underlines the necessity for ongoing research to distinguish between those cooling down and those that may eventually become active again.