Melting glaciers could make volcanic eruptions more explosive and frequent, worsening climate change in the process, scientists have warned.
Hundreds of volcanoes in Antarctica, Russia, New Zealand, and North America rest beneath glaciers. But as the planet warms and these ice sheets melt and retreat, these volcanoes are likely to become more active, according to the authors of a new study analyzing the activity of six volcanoes in southern Chile during the last ice age.
The researchers will present their findings Wednesday (July 8) at the 2025 Goldschmidt Conference in Prague.
“Glaciers tend to suppress the volume of eruptions from the volcanoes beneath them. But as glaciers retreat due to climate change, our findings suggest these volcanoes go on to erupt more frequently and more explosively,” study lead-author Pablo Moreno Yaeger, a graduate student at the University of Wisconsin-Madison, said in a statement.
Scientists first theorized that melting ice could impact volcanoes in the 1970s. The underlying process is a simple one — the weight of glaciers exerts a downward force on Earth’s crust and mantle, so when the ice retreats, subterranean gases and magma expand, leading to pressure buildups that fuel explosive eruptions.
Related: ‘Cryptic carbon’ may leak from volcanoes millions of years after eruptions end
This process is already known to have fundamentally reshaped Iceland, which is located above the diverging North American and Eurasian tectonic plates. In 2002, scientists calculated changes to Iceland’s volcanic activity as its glaciers retreated at the end of the last ice age, roughly 10,000 years ago. The island’s volcanoes responded with a surge of eruptions, blowing at a rate 30 to 50 times greater than they had before or since.
Yet the danger that could be lurking inside continental volcanic systems remains understudied. To investigate it, the geoscientists looked at six volcanoes located in southern Chile, including the now dormant Mocho-Choshuenco volcano, and how they responded to the melting of the Patagonian Ice Sheet thousands of years ago.
By using the radioactive decay of argon released by the region’s erupting volcanoes as an isotopic clock, and by studying crystals that began forming inside magmatic rocks spewed when the volcanoes erupted, the researchers were able to track the region’s volcanic activity and its relationship to its vanishing ice.
They found that between 26,000 to 18,000 years ago, during the peak of the last ice age, ice cover tamped down the volume of eruptions, causing a giant reservoir of magma to accumulate beneath the region’s surface. When the ice sheet melted, pressure grew inside this reservoir and was eventually released to form the Mocho-Choshuenco volcano.
This threat is planetary in scope: 245 of the world’s potentially active volcanoes lie underneath or within 3 miles (5 kilometers) of ice, according to a 2020 study.
“The key requirement for increased explosivity is initially having a very thick glacial coverage over a magma chamber, and the trigger point is when these glaciers start to retreat, releasing pressure — which is currently happening in places like Antarctica,” Moreno Yaeger said.
He added that other regions of concern include North America, New Zealand and Russia, saying these areas “warrant closer scientific attention.”
Over short time periods, eruptions typically release sulfate aerosols that reflect sunlight back into space. This has led to cooling events following past eruptions, some of which have triggered major famines. Yet over the long term, the greenhouse gases from these volcanoes will likely cause climate change to accelerate, the researchers said.
“Over time the cumulative effect of multiple eruptions can contribute to long-term global warming because of a buildup of greenhouse gases,” Moreno Yaeger said. “This creates a positive feedback loop, where melting glaciers trigger eruptions, and the eruptions in turn could contribute to further warming and melting.”