Glaciers melting from climate change may reawaken the world’s most dangerous volcanoes
As the planet warms, humans could face a much more risky and explosive future.
Published December 30, 2025
A powerful swarm of earthquakes in January suggested one of Iceland’s giant “ice volcanoes” may be awakening after a decade of slumber. In the months that followed, more earthquakes have rocked the ground.
They are a sign that hot, viscous magma is flowing to the roots of Bardarbunga, which lies beneath Europe’s largest glacier Vatnajökull. It’s not a matter of if Bardarbunga erupts, but when — and it could be a big one.
The volcano’s 25 square-mile caldera is filled with ice, and when lava and ice meet, the consequences are explosive. When it last awoke in 2014, Bardarbunga produced Iceland’s biggest eruption in more than 200 years, spewing out fountains of lava hundreds of feet high.
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Scientists in Iceland have their eyes on this volcano, along with others nestled under the frozen landscape — roughly half of the country’s 34 active volcanic systems are covered in ice. They are trying to unravel whether a decades-old theory could be correct: that retreating ice, fueled by the climate crisis, is triggering more frequent and more explosive volcanic eruptions.
At the heart of this quest is an effort to understand how the planet functions at a fundamental level, and how what humans are doing at the surface — namely, warming the Earth — could be interacting with natural processes deep beneath the ground.
It’s “a connection that we haven’t always understood,” said Ben Edwards, a professor of geosciences at Dickinson College.
If the theory is proven correct, the consequences could be enormous, spelling a much more risky, explosive future, as global warming continues to eat away ice sheets and glaciers at a frenetic pace.
Fire under the ice
Iceland is a perfect natural laboratory for studying the intricacies of volcanoes and ice.
Perched astride two tectonic plates that are wrenching apart, and above a plume of superheated rock, it’s a hotspot of volcanic activity. It’s also icy, albeit much less so than in the past.
About 15,000 years ago, during the last Ice Age, the country was enveloped in a thick ice sheet. Over the course of just a few thousand years, much of it disappeared, forging a new landscape. Glaciers now cover only around 10% of Iceland.
When the ice vanished, something unusual followed. There was a pulse of volcanic activity, with eruption rates increasing an estimated 30- to 50-fold, said Michelle Parks, coordinator of volcano deformation monitoring at the Icelandic Meteorological Office. This increased volcanic activity lasted roughly 1,500 years.
Now the remaining ice is retreating rapidly, this time driven by human-caused climate change, and Parks and other scientists are trying to figure out if this effect might happen again.
What they find out will have consequences well beyond Iceland. There are approximately 245 volcanoes around the world fully or partly covered by ice, according to a 2020 mapping study, co-authored by Edwards.
These “glaciated volcanoes” are found in Alaska; down the west coast of North America, from British Columbia to northern California; along the west coast of South America; in eastern Russia’s Kamchatka Peninsula and even hidden beneath Antarctica’s vast ice sheet.
Around 160 million people live within 60 miles of an ice-covered volcano, and roughly 200,000 live within 3 miles, according to Edward’s study, meaning a more explosive future could have a profound impact on human lives.
Magma under pressure
Scientists are still unraveling the complex ways melting ice affects volcanic activity, but there is general agreement over how the relationship may unfold.
It works like this: Ice sheets and glaciers lie on top of volcanoes like thick, weighted blankets, exerting a downward pressure on the Earth.
If they melt rapidly, that pressure is reduced, allowing the ground to gradually inflate. In its simplest terms, the effect is similar to when you stand up from a couch and the cushions slowly rise back up — just with land, it happens over centuries rather than seconds.
Scientists believe the change in pressure does two things. First, it affects what’s happening deep beneath the ground in the mantle where magma is formed.
In places like Iceland, where the crust is pulling apart, hot rock moves toward the surface to fill the space. As it rises upward, the pressure drops, allowing it to melt and form magma.
Lava flows along a fissure of the Bardarbunga volcanic system during the volcano’s 2014 eruption. (Marco Nescher/Reuters) Water from melting ice runs off of Falljökull glacier, one of Vatnajökull’s glacier tongues, in 2021. (Sean Gallup/Getty Images) An aerial view of the Svínafellsjökull Glacier, part of the Vatnajökull ice cap, in 2021. (Sean Gallup/Getty Images)
A melting glacier is effectively relieving the pressure below, allowing more magma to be produced. And this additional magma “will cause more and/or larger volcanic eruptions,” said Allie Coonin, a geophysics researcher at Brown University.
In Iceland, Parks and her colleagues ran computer models that estimated at least twice as much magma is now being generated under Iceland because of the pressure release from melting glaciers. The big uncertainty is how long it may take to make its way to the surface.
Melting ice also affects existing magma bodies that lie just a few miles beneath volcanoes. Forces within the Earth, induced by the melting ice, can influence how the magma moves toward the surface and how much magma needs to accumulate before the next eruption is triggered.
Exactly how the magma chamber reacts will depend on its geometry, Parks said. For some, the impacts of melting ice may mean more eruptions; for others, it may delay them but allow more magma to collect close to the surface, meaning a larger eruption further down the line.
What’s happening underground
As a glacier’s weight pushes down on the Earth’s crust and mantle, it can reduce magma production.
When ice melts, pressure is released and more rock can melt forming magma. It can also affect forces within the Earth, changing the movement of magma.
Increased magma production
As a glacier’s weight pushes down on the Earth’s crust and mantle, it can reduce magma production.
When ice melts, pressure is released and more rock can melt forming magma. It can also affect forces within the Earth, changing the movement of magma.
Increased magma production
As a glacier’s weight pushes down on the Earth’s crust and mantle, it can reduce magma production.
When ice melts, pressure is released and more rock can melt forming magma. It can also affect forces within the Earth, changing the movement of magma.
Increased magma production
As a glacier’s weight pushes down on the Earth’s crust and mantle, it can reduce magma production.
When ice melts, pressure is released and more rock can melt forming magma. It can also affect forces within the Earth, changing the movement of magma.
Increased magma production
A hotter planet could mean a more fiery one
The strongest evidence for the theory comes from Iceland, but scientists are also looking at the west coast of South America, specifically the Chilean Andes.
Its geology is different and more complex than Iceland’s. This is a subduction zone, where tectonic plates meet, pushing the colder, denser plate slowly downward. “That kind of stirs up the inner part of the earth,” Dickinson College’s Edwards said. The crust here is thicker and magma is produced deeper underground.
These volcanoes are also closer to people, with hundreds of thousands potentially in the path of an eruption.
Pablo Moreno-Yaeger, a researcher at the University of Wisconsin-Madison, has been looking into the region’s deep past to better understand how its future may unfold.
He analyzed six volcanoes in southern Chile, including the now-dormant Mocho-Choshuenco, all of which were blanketed by the Patagonian ice sheet at the peak of the last Ice Age, around 26,000 to 18,000 years ago.
By analyzing crystals in erupted rocks, he was able to precisely date previous eruptions and track how the ice cap’s retreat affected volcanic activity thousands of years ago.
Chile’s Mocho-Choshuenco volcano in 2016. (Complete Photography/Alamy)
He found the thick ice had suppressed eruptions and allowed the formation of a huge magma chamber about 6 to 9 miles beneath the ground. The ice sheet melted rapidly at the end of the Ice Age, and the sudden loss of pressure caused the crust to relax and gases in the magma to expand, according to research co-authored by Moreno-Yaeger, which is awaiting peer review.
The result: explosive volcanic eruptions, emptying the chamber of all the magma that was pent up and unable to erupt when the glaciers were present, like opening the top of a jostled soda bottle.
It’s a window into a possible future. Mocho-Choshuenco is covered by an ice cap that could all but vanish by the end of the century if climate pollution continues to rise.
This phenomenon could also affect other continental regions, including Antarctica, where around 130 active and dormant volcanoes lie under the world’s largest ice sheet.
“There’s more ice in Antarctica by quite a large way than all of the rest of ice on Earth combined,” said Maximillian Van Wyk de Vries, assistant professor in natural hazards at the University of Cambridge, who co-authored a 2017 study identifying nearly 100 volcanoes underneath the ice along the continent’s west coast.
Antarctica is probably the place people wonder about most because so little is known about these volcanoes, Edwards said. “What kind of impact could happen if we really rapidly destabilize the West Antarctic Ice Sheet?” Edwards asked.
A flurry of volcanic eruptions could contribute to the melting of the ice sheet, which is already experiencing alarming changes, ramping up global sea levels. Its vastness may provide protection, however. Even if all the continent’s volcanoes erupted at once, “they’d melt an absolutely tiny fraction of it,” said Van Wyk de Vries.
The deadly mix of lava and ice
A huge uncertainty for ice-covered volcanoes across the world is how long it will take them to react to the loss of ice. Moreno-Yaeger’s work found a lag of a few thousand years in Chile, an instant in geological terms but very gradual on human timescales.
Today, scientists digging into the question say impacts could unfold in decades; or it could take centuries. Humans still have such a shallow understanding of the complex interactions between the atmosphere, water and the Earth’s crust, “we can’t be confident about everything that’s going to happen,” said David Pyle, a professor of Earth sciences at the University of Oxford.
It’s vital to keep learning though; ice-covered volcanoes are among the most dangerous on Earth.
The glacier-capped Nevado del Ruiz, about 80 miles west of Colombia’s capital city Bogotá, is a visceral example of how catastrophic the mix of fire and ice can be. The volcano was known as the “sleeping lion,” but in the evening of November 13, 1985, it woke up.
The eruption spewed out screaming-hot lava, which melted ice and sent rivers of mud roaring down the slopes toward the valley town of Armero, around 30 miles away. With few warnings and little time to flee, residents were trapped. The town was buried; at least 23,000 people lost their lives.
Nevado del Ruiz was the deadliest eruption of the last 100 years. It was a “very visible example of what happens with a relatively small eruption interacting with an ice cap,” Pyle said.
Mud and debris bury the town of Armero, Colombia, after the eruption of Nevado del Ruiz in November 1985. (Jacques Langevin/Sygma/Getty) A helicopter evacuates victims of the 1985 Nevado del Ruiz eruption while another is carried on a stretcher on November 16, 1985. (Oscar Sabetta/Reuters) People gather around the grave of Omaira Sanchez, one of the victims of the 1985 eruption, 10 years after her death on November 13, 1995. (Pedro Ugarte/AFP/Getty Images)
Ice-covered volcanoes can produce huge quantities of water very quickly, triggering volcanic mud flows and floods that can travel extremely fast and bring devastation. Even if melting has a small effect on volcanoes, “that can still be important because of how dangerous these areas are,” Van Wyk de Vries said.
But there is another possibility, too. Disappearing ice could make some eruptions less disastrous, because there is less ice to trigger devastating floods and mudflows. Whether some volcanoes could become safer as the world warms, however, is a question “for which we don’t have a particularly good answer still,” Van Wyk de Vries said.
What is certain is that global temperatures are ticking up and will alter landscapes dramatically. “These are environments that are going to change massively … a lot of these glaciated volcanoes are not going to be glaciated in 100 years’ time,” Van Wyk de Vries said.
The quest to truly understand volcanic responses to melting ice is likely to be a long one.
Volcanoes are hard to study. Many are in the planet’s most inaccessible regions — especially those under ice — and most of their activity happens over epic time periods, deep beneath the ground, hidden from human eyes.
The interactions between the climate crisis and volcanoes are also endlessly complicated, and work both ways: volcanoes can shape climate change as well as being affected by it. When Mount Tambora erupted in Indonesia in 1815, it sent plumes of sun-reflecting particles into the atmosphere, dimming the sun and ushering in a “year without summer,” where global temperatures plunged.
With multiple eruptions, however, the effects can reverse due to a buildup of planet-heating gases. “This creates a positive feedback loop, where melting glaciers trigger eruptions, and the eruptions in turn could contribute to further warming and melting,” said Moreno-Yaeger.
The problem is that we don’t yet have a good idea of what will happen, he said. “When we talk about climate change, we are always talking about chaos.”
