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A photographer approaches the craters of the active Sundhnúkur volcano on the Reykjanes peninsula near Grindavik, Iceland on June 2, 2024. John Moore / Getty Images

Ice loss from melting glaciers around the world due to global heating could cause pressure to be released from volcanic magma chambers located deep underground.

The process — already seen in Iceland — makes volcanic eruptions more frequent and powerful, according to new research conducted in the Chilean Andes.

“As glaciers retreat due to climate change, our findings suggest these volcanoes go on to erupt more frequently and more explosively,” said lead author of the research Pablo Moreno-Yaeger, a graduate student at the University of Wisconsin-Madison, as The Guardian reported. “We found that following deglaciation, the volcano starts to erupt way more, and also changes composition.”

While eruptions are suppressed, magma melts crustal rocks, making the molten rock more viscous and setting the stage for it to be more explosive when it erupts.

Melting glaciers and ice caps could unleash wave of volcanic eruptions, study says

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— The Guardian (@theguardian.com) July 7, 2025 at 7:18 PM

“Glacial loading and unloading can impact eruptive outputs at mid- to high-latitude arc volcanoes, yet the influence on magma storage conditions remains poorly understood. Mocho-Choshuenco volcano in the Andean Southern Volcanic Zone has been impacted by the advance and retreat of the Patagonian ice sheet,” the authors of the study wrote.

The findings of the study were presented on July 8 at the Goldschmidt Conference in Prague. The research suggests that hundreds of subglacial volcanoes that have been dormant — especially in Antarctica — have the potential to become active as glacial retreat accelerates under climate change, a press release from the Goldschmidt Conference said.

Since the 1970s, scientists have been aware of the link between increased volcanic activity and retreating glaciers in Iceland. However, this is among the first studies to examine this type of event in continental volcanic systems.

The findings could help scientists better comprehend, as well as predict, volcanic activity in glacial regions.

To study how past volcanic behavior was influenced by the retreat and advance of the Patagonian Ice Sheet, the researchers used crystal analysis and argon dating across six Chilean volcanoes, including now-dormant Mocho-Choshuenco.

Melting glaciers may increase the frequency and explosiveness of volcanic eruptions, potentially impacting global climate as retreating ice reduces pressure on magma chambers beneath volcanoes.

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— Science X / Phys.org (@sciencex.bsky.social) July 7, 2025 at 7:02 PM

Through the analysis of erupted rock crystals and precisely dated earlier eruptions, the research team was able to track how the pressure and weight of glacial ice altered the characteristics of underground magma.

They discovered that thick ice cover at the peak of the last Ice Age roughly 26,000 to 18,000 years ago suppressed eruption volume, allowing a large silica-rich magma reservoir to accumulate 10 to 15 kilometers underground.

The sudden loss of weight from the rapidly melting ice sheet as the last Ice Age ended caused a relaxation of the crust and an expansion of gases in the magma. The pressure led to explosive volcanic eruptions deep within the reservoir, causing formation of the volcano.

“Glaciers tend to suppress the volume of eruptions from the volcanoes beneath them,” Moreno-Yaeger said. “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 the findings suggested the phenomenon wasn’t limited to Iceland, but could happen all over the world.

“Other continental regions, like parts of North America, New Zealand and Russia, also now warrant closer scientific attention,” Moreno-Yaeger said.

Although in geological terms the volcanoes’ response to glacial melt is almost instant, changes to the magma system are gradual, occurring over centuries, which provides some time for monitoring and warnings to be issued.

The team noted that an increase in volcanic activity could impact the whole planet. Eruptions release aerosols that can provide temporary cooling in the short-term. This was the case following the eruption of Mount Pinatubo in the Philippines in 1991. The explosion reduced global temperatures by roughly 0.5 degrees Celsius.

However, multiple eruptions have a reverse effect.

“Over time the cumulative effect of multiple eruptions can contribute to long-term global warming because of a buildup of greenhouse gases,” Moreno-Yaeger explained. “This creates a positive feedback loop, where melting glaciers trigger eruptions, and the eruptions in turn could contribute to further warming and melting.”

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Ever been late because you misread a clock? Sometimes, the “clocks” geologists use to date events can also be misread. Unravelling Earth’s 4.5-billion-year history with rocks is tricky business.

Case in point: the discovery of an ancient meteorite impact crater was recently reported in the remote Pilbara region of Western Australia. The original study, by a different group, made headlines with the claim the crater formed 3.5 billion years ago. If true, it would be Earth’s oldest by far.

As it turns out, we’d also been investigating the same site. Our results are published in Science Advances today. While we agree that this is the site of an ancient meteorite impact, we have reached different conclusions about its age, size and significance.

Related: Record Discovery: Impact Crater in Australia’s Outback Oldest by a Billion Years

Let’s consider the claims made about this fascinating crater.

One impact crater, two versions of events

Planetary scientists search for ancient impacts to learn about Earth’s early formation. So far, nobody has found an impact crater older than the 2.23-billion-year-old Yarrabubba structure, also in Australia. (Some of the authors from both 2025 Pilbara studies were coauthors on the 2020 Yarrabubba study.)

The new contender is located in an area called North Pole Dome. Despite the name, this isn’t where Santa lives. It’s an arid, hot, ochre-stained landscape.

The first report on the new crater claimed it formed 3.5 billion years ago, and was more than 100 kilometres in diameter. It was proposed that such a large impact might have played a role in forming continental crust in the Pilbara. More speculatively, the researchers also suggested it may have influenced early life.

Our study concludes the impact actually happened much later, sometime after 2.7 billion years ago. This is at least 800 million years younger than the earlier estimate (and we think it’s probably even younger; more on that in a moment).

We also determined the crater was much smaller – about 16 km in diameter. In our view, this impact was too young and too small to have influenced continent formation or early life.

So how could two studies arrive at such different findings?

Subtle clues of an impact

The originally circular crater is deeply eroded, leaving only subtle clues on the landscape. However, among the rust-coloured basalts are unique telltale signs of meteorite impact: shatter cones.

Shatter cones are distinctive fossilised imprints of shock waves that have passed through rocks. Their unique conical shapes form under brief but immense pressure where a meteorite strikes Earth.

Both studies found shatter cones, and agree the site is an ancient impact.

This new crater also needed a name. We consulted the local Aboriginal people, the Nyamal, who shared the traditional name for this place and its people: Miralga. The “Miralga impact structure” name recognises this heritage.

Determining the timing of the impact

The impact age was estimated by field observations, as neither study found material likely to yield an impact age by radiometric dating – a method that uses measurements of radioactive isotopes.

Both studies applied a geological principle called the law of superposition. This states that rock layers get deposited one on top of another over time, so rocks on top are younger than those below.

The first group found shatter cones within and below a sedimentary layer known to have been deposited 3.47 billion years ago, but no shatter cones in younger rocks above this layer. This meant the impact occurred during deposition of the sedimentary layer.

Their observation seemed to be a “smoking gun” for an impact 3.47 billion years ago.

As it turns out, there was more to the story.

Our investigation found shatter cones in the same 3.47 billion-year-old rocks, but also in younger overlying rocks, including lavas known to have erupted 2.77 billion years ago.

The impact had to occur after the formation of the youngest rocks that contained shatter cones, meaning sometime after the 2.77-billion-year-old lavas.

At the moment, we don’t know precisely how young the crater is. We can only constrain the impact to have occurred between 2.7 billion and 400 million years ago. We’re working on dating the impact by isotopic methods, but these results aren’t yet in.

Smaller than originally thought

We made the first map showing where shatter cones are found. There are many hundreds over an area 6km across. From this map and their orientations, we calculate the original crater was about 16km in diameter.

A 16km crater is a far cry from the original estimate of more than 100km. It’s too small to have influenced the formation of continents or life. By the time of the impact, the Pilbara was already quite old.

A new connection to Mars

Science is a self-policing sport. Claims of discovery are based on data available at the time, but they often require modification based on new data or observations.

While it’s not the world’s oldest, the Miralga impact is scientifically unique, as craters formed in basalt are rare. Most basalts there formed 3.47 billion years ago, making them the oldest shocked target rocks known.

Prior to impact, these ancient basalts had been chemically altered by seawater. Sedimentary rocks nearby also contain the earliest well-established fossils on Earth. Such rocks likely covered much of early Earth and Mars.

This makes the Miralga impact structure a playground for planetary scientists studying the cratered surface (and maybe early life) of Mars. It’s an easily accessible proving ground for Mars exploration instruments and imagery, right here on Earth.

Aaron J. Cavosie, Senior Lecturer, School of Earth and Planetary Sciences, Curtin University and Alec Brenner, Postdoc, Earth and Planetary Sciences, Yale University

This article is republished from The Conversation under a Creative Commons license. Read the original article.