Add to the long list of global warming concerns that melting ice caps could trigger more volcanic eruptions. 
Worse, researchers said Monday at a scientific conference in Prague, the increasing volcanic activity holds the potential for a range of long-term climate feedbacks, as some volcanoes in Antarctica could accelerate ice melt from below while others could be so explosive that they send climate-altering material into the upper layers of the atmosphere.

The research funded by the National Science Foundation studied the chemistry of rocks at six volcanoes in the Chilean Andes, where the scientists were able to detail changes in the magma below the ice or underground over the millennia of the most recent ice age, and to document how volcanic activity increased when the ice melted.

University of Wisconsin–Madison geoscientist Brad Singer, who led the research, said there are clear signs that thick ice caps act as lids on volcanoes, which can blow their tops when the icy cover melts or slides away.

“Right after the glaciers melted and the load of the ice came off, in the plumbing systems we studied, we see significant changes not only in eruptive rate, but in the compositions of the eruptive products,” he said.

There is at least circumstantial evidence that, during the peak of the last ice age, about 14,000 to 20,000 years ago, the magma suppressed by the ice pooled and partly crystallized with silica formations that trap gases. That can drive eruptions of fiery lava and ash flows, and send clouds of ash several miles high that can reach the stratosphere.

“When you take the load off, it’s just like opening a Coca-Cola bottle or a champagne bottle,” Singer said. “It’s under pressure, and the dissolved gasses in the melt come out as bubbles.”

Singer has been studying the geology and volcanic activity in the Andes for about 30 years. He said the idea to look closely at the effects of ice loading and unloading during the last glacial cycle has been simmering for a long time.

Most of the work focused on what happened after ice melted, rather than what was going on during the peak of glaciation, he said. The new research was partly inspired by other work that looked at the traces of eruptions left on the surface, like ash layers in pond sediments.

“When you take the load off, it’s just like opening a Coca-Cola bottle or a champagne bottle.”

— Brad Singer, University of Wisconsin–Madison geoscientist

Looking farther back in time helps present a clearer picture of what may be going on inside the many volcanoes currently buried beneath Antarctica’s vast ice sheets, he added.

Of particular concern are more than 100 volcanoes under the 760,000-square-mile West Antarctic Ice Sheet, one of the regions of the continent where warm ocean currents are already melting floating ice shelves from below.

“Many volcanoes have been detected geophysically beneath the ice sheet there,” Singer said. “There is probably a rifted area in the crust underneath the big, thick, West Antarctic Ice Sheet.”

The ice sheet overlying a zone of active volcanoes can magnify the volatility of both the glaciers and the fiery mountains. 

“What we’re finding in our work is that taking off the ice rapidly increases the frequency of eruptions,” he said. “Well, if those volcanoes are sitting at the base of the ice, and they start to be able to erupt more frequently, they’re going to start to melt the base of the ice.”

The pressure of the ice can also change how what’s inside the volcano cooks, said co-author Pablo Moreno-Yaeger.

The ice, like the lid on a cooking pot, changes the dynamics of what is happening in the volcano beneath it, which “could change the composition beneath the volcano,” Moreno-Yaeger said. “That will then generate more explosive eruptions when that lid is lifted.”

He said the scientists have been studying the relationship between ice caps and volcanic activity in Iceland since the 1970s. The island in the North Atlantic sits on a thin part of Earth’s crust. Previous research found that even volcanoes erupting beneath that ice release heat-trapping carbon dioxide into the atmosphere. Detailed measurements at the Katla volcano in 2016 and 2017 showed it releasing between 12,000 and 24,000 metric tons of CO2 per day, more than previous estimates for all of Iceland’s volcanoes combined.

And the weight of the water released by melting ice sheets could drive other geologic feedbacks.

In 2024, another team of researchers wrote in Seismological Research Letters that the increasing hydraulic pressure from seas rising with water from melting continental ice sheets could drive an increase in earthquakes. That process has been documented in earthquakes that occur around reservoirs when their water levels are high.

“This new work strengthens the evidence for the links between ice-loading (modulated by climate) and volcanism,” University of Oxford volcanologist David Pyle wrote in an email. Pyle was not involved in the new research but has done related studies.

In the case of the volcanoes in the Andes, the volcanic response lagged a few thousand years behind the melting of the ice age glacial cap, Moreno-Yaeger said.

“It’s not an immediate response,” he said. “In terms of this volcanic eruption, we really don’t know when they will happen.” The new paper focuses on the response of one type of volcano, he added, and other types of volcanoes with different minerals could respond on a different timescale.

Singer, the lead author, called it a “negative feedback loop” for the climate.

“If you start getting more eruptions underneath ice that is thinning, you could more rapidly cause the ice sheet to slide into the ocean and cause sea level rise,” he said. “That is not something we want to see, but maybe it’s in our future.”