An international group of scientists is researching the impact of climate change and glacier retreat on seismic activity and volcanic eruptions in Iceland. One hypothesis suggests that up to three times more magma is forming beneath the surface due to glacier retreat — and that this process is already underway, reports RÚV.

The study, part of the ongoing ISVOLC project, led by Michelle Parks from the Icelandic Meteorological Office alongside geophysicist Freysteinn Sigmundsson from the University of Iceland, is examining how Iceland’s changing glaciers could be linked to seismic activity and volcanic eruptions. The ISVOLC project, which began in April 2023 and will span three years, includes 20 scientists from 11 institutions worldwide. Its main goal is to assess how the melting of Iceland’s glaciers affects underground magma systems and to explore possible changes in volcanic and seismic activity. The project will also construct a comprehensive database of Iceland’s glacial changes since 1890, creating high-resolution, 3D time-based models that predict land uplift and magma production as glaciers continue to thin.

According to Freysteinn, modeling suggests that two to three times more magma is forming beneath Iceland now compared to before the glaciers started retreating. To examine this hypothesis, scientists are specifically studying the effects of glacial changes on four volcanic systems: Katla, Askja, Grímsvötn, and Bárðarbunga.

“There is a concerted effort to study the links between glacial changes and volcanic activity,” says Freysteinn, adding that these four volcanoes were chosen is that they are the most active ones lying beneath glaciers in Iceland.

How pressure reduction affects magma systems 

Freysteinn says that throughout geological history, increased volcanic activity has followed glacial periods. When the Ice Age glacier retreated from Iceland around ten thousand years ago, a period of intense volcanic activity began, which “in fact lasted for several thousand years until all glacial ice had disappeared and the crust reached equilibrium,” says Freysteinn.

It is known that major changes on the Earth’s surface can influence what happens beneath it. “And now we’re seeing significant glacial thinning, both in Iceland and globally,” says Freysteinn. This leads to a variety of conclusions.

“We know how much these glaciers have thinned in Iceland since 1890,” he says, “and we can try to assess how the pressure beneath the ground has changed as a result of this thinning.”

“We know how the glacial load has changed, and we expect that with such significant changes in the glaciers, there will be a response within the Earth, and the land will begin to lift,” he says.

Precise measurements of crustal movements over recent decades have revealed that widespread uplift is occurring in Iceland due to glacial thinning. A large portion of Iceland’s central highlands is rising by 20 to 30 millimeters per year due to glacier retreat.

This reduction in pressure beneath Iceland affects the magma systems under volcanoes and influences how magma forms.

“Magma generally forms beneath Iceland due to pressure relief because we have an upwelling zone in the Earth’s mantle. As pressure decreases when mantle material or deep-earth material moves towards the surface, new magma is created,” he explains.

However, as the glaciers are now retreating, the pressure is decreasing even further, resulting in additional magma production. Freysteinn says that according to the models used in this research project, it is estimated that two to three times more magma is forming under Iceland today compared to when the glaciers were stable.

Increased volcanic activity possible

When asked whether this could lead to increased volcanic activity in Iceland, Freysteinn acknowledges that it’s a definite possibility.

“We’re trying to better understand what happens to this magma being generated,” he says.

“This could indeed impact volcanic activity, and one potential outcome is that this additional magma reaches the surface. However, this could take some time, meaning that although magma is forming more rapidly beneath Iceland now, it’s uncertain if or when it will reach the surface,” Freysteinn explains.

At Askja, located in Iceland’s northern volcanic zone near Vatnajökull, there has been substantial uplift and an increase in pressure. In recent years, Askja has risen by over 80 centimeters, likely due to the flow of magma into shallow depths beneath it.

Freysteinn notes that this process has been ongoing for several years, prompting investigations into whether it’s connected to newly formed magma approaching the volcanic system. Askja has become a focal point for these studies because of significant changes in the area since 2021.

There are various signs that the effects of glacier retreat could be multifaceted. First, it leads to increased magma production, but it could also alter magma chambers and shallow reservoirs within the crust.

“This may occur at depths between three and fifteen kilometers,” Freysteinn says, adding that it might also lead to new areas of magma movement or volcanic activity.

While more magma is forming, Freysteinn emphasises that it’s still uncertain if or when it will reach the surface — one of the key questions this project aims to answer.

One of the possible consequences of increased magma formation is that eruptions could become more powerful due to the larger volumes of magma accumulating.

“When magma is stored at shallow depths within the crust, just a few kilometres down, the effects could manifest as either more frequent eruptions or increased accumulation. There are certain indications of a slightly altered eruption pattern at Katla compared to recent decades,” says Freysteinn.

Katla is Iceland’s fourth most active volcanic system, having erupted at least 21 times over the past 1,100 years. Its last eruption occurred in 1918. Scientists have long speculated about when Katla will erupt again, with the average interval between eruptions historically around 50 years. This year marks 106 years since Katla’s last eruption.

“It’s possible that more magma may accumulate, which could mean a more hazardous eruption if it eventually reaches the surface in a major Katla event,” Freysteinn adds.

“This project is ongoing, and we hope to significantly improve our understanding of these processes through the research being conducted,” he concludes.