Researchers Warn: Melting Glaciers and Ice Caps May Trigger Wave of Volcanic Eruptions

The accelerated melting of glaciers does not only threaten the oceans and polar regions. According to a study presented recently at the Goldschmidt international conference in Prague by researchers from the University of Wisconsin-Madison, the decline in ice could also wake up volcanoes so far asleep. By relaxing the pressure exerted on the earth's crust, the disappearance of the glaciers promotes the rise of the magma and increases the risk of explosive eruptions.

A domino effect between glaciers and magma

The relationship between glaciers and volcanic activity is based on a simple physical principle, but to formidable consequences. The glaciers, by their colossal mass, exert an enormous pressure on the earth's crust. This force acts as a giant cover that keeps magma under control. It prevents volcanic gases from expanding and escaping. When the climate warms up and the glaciers melt, this weight gradually disappears. The earthly crust, hitherto compressed, relaxes. This decompression leads to a drop in pressure on the magmatic chambers, sometimes located 10 or 15 kilometers deep.

Under these conditions, gases dissolved in magma – mainly water vapor, carbon dioxide and sulfur dioxide – expanded quickly. The magma becomes more mobile and its viscosity can increase if it mixes with melted rocks of the crust. This combination creates an environment conducive to explosive eruptions. Pablo Moreno-Yaeger, who led research at the University of Wisconsin-Madison, explains to the Guardian: ” The withdrawal of the glaciers releases the pressure that contained the magma. This triggers more frequent and often more violent volcanic activity».

This phenomenon was confirmed in Iceland after the last glacial period, where the decline in glacial caps coincided with a multiplication by 30 to 50 of eruptions. Today, the same conditions are taking shape in regions such as Patagonia, Alaska and Antarctica, which are home to hundreds of volcanoes under the ice.

The Chilean case: dormant volcanoes, but under pressure from glaciers

In the Andes in southern Chile, scientists have found an ideal ground to analyze the impact of glaciers on volcanic activity. The team studied six volcanoes, including Mocho-Choshuenco, a stratovolcancan currently inactive. To reassemble the thread of its eruptive history, the researchers combined two advanced techniques. Namely: isotopic dating at the Argon and the mineralogical analysis of crystals trapped in volcanic rocks. These methods make it possible to precisely estimate the age of the eruptions and the conditions of formation of the magma.

Their results reveal that between 26,000 and 18,000 years old, the region was covered by the Patagonian ice cap, almost 1,500 meters thick. This mass of ice exerted enormous pressure on the earth's crust, stabilizing the underlying magmatic system. The eruptions were rare and not very bulky. During this period, a gigantic magma tank rich in silica was able to accumulate at a depth of 10 to 15 kilometers.

But from the age of 13,000, the rapid melting of this cap released the pressure. This sudden relief allowed the gases contained in the magma of expanding. The rise of this more viscous magma has led to a succession of explosive eruptions, reshaping the Andean landscape. “”After the deglaciation, the volcano becomes much more active and its thicker magma increases the destructive potential of the eruptions“, Underlines Moreno-Yaeger. These observations provide a key to understanding the current risks in other glacial areas.

A global risk, from Antarctica glaciers to Russia

The team's work then highlights a largely underestimated vulnerability on a planetary scale. According to their analyzes, 245 potentially active volcanoes are buried under glaciers or in the immediate vicinity of glacial caps. This configuration creates a latent risk in regions long deemed stable. Western Antarctica alone concentrates more than 100 subglacial volcanic buildings. Their behavior is still little studied, for lack of direct access. However, the loss of several kilometers of ice could radically change the balance of the earth's crust.

The authors also point out that this phenomenon is not limited to the poles. Continental areas located in Alaska, Eastern Russia and New Zealand shelter volcanoes under glacial influence. These regions are exposed to an acceleration of the melting, likely to release the constraints on magmatic systems. “”Other parts of the globe, long ignored, could become households of increased volcanic activity“Warns Moreno-Yaeger. The geological precedents in Iceland, combined with current climatic projections, strengthen the hypothesis of a future marked by more diffuse and unpredictable volcanic instability.

Between temporary cooling and sustainable warming

Volcanoes, in eruption, are not content to upset the landscapes. They also influence the climate in a complex way. When a volcano projects millions of tonnes of ash and sulfated aerosols into the atmosphere, these particles form a screen that reflects part of the solar radiation. This mechanism can cause temporary cooling, as after the eruption of Mount Pinatubo in 1991. It had lowered the global temperature by 0.5 ° C for several months. But this regulation capacity remains short -lived and limited to isolated events.

Pablo Moreno-Yaeger and his colleagues warn against another dynamic, much more worrying. A succession of eruptions in glacial regions could release large quantities of greenhouse gases. And in particular carbon dioxide and methane, stored in magma. At the level of several decades, these emissions would help accelerate global warming. “”This creates a feedback loop: the melting of glaciers stimulates volcanic activity, which in turn intensifies the cast iron», Explains Moreno-Yaeger toLive science. This scenario, still little integrated into climate models, makes global forecasts more uncertain, even dramatic.

Researchers call to intensify surveillance efforts in all ice areas to anticipate the effects of this tilting. Especially since research on climate-volcanism interaction remains fragmentary, despite its major implications for infrastructure, ecosystems and population security. “”Understanding these processes remains essential to anticipate their consequences, local and global», Insists Moreno-Yaeger. Without alarmism, this observation underlines the need to better integrate these risks into resilience strategies in the face of the climate crisis.

Source: Abstract conference. Expansion and contraction of the Patagonian Ice Sheet and It's Influence on Magma Storage Beneath Mocho-Choshuenco Volcano. zenodo.org/records/15021753