‘Rapid’ Magma Rise, Radar Images, Eruption Latest

A “rapid, ongoing” rise in the Earth’s crust is occurring “considerably faster than before” underneath a part of Iceland that has seen heightened tectonic activity in recent weeks, the nation’s meteorological office has said, prompting concerns of an imminent volcanic eruption.

In an update on Monday, the Icelandic Met Office said there had been around 700 earthquakes between midnight and 1:20 p.m. UT that day (8 a.m. ET) around the site of a “magma intrusion,” the largest being a magnitude 2.7 tremor near the Hagafell mountain.

Between 1,500 and 1,800 earthquakes a day have occurred since November 10, prompting local authorities to evacuate the coastal fishing town of Grindavik. The tectonic activity has seen cracks appear in the ground and across roads in the area.

Experts suggested that a sudden shift in tectonic plates had prompted magma under the surface to push upwards, with the most likely location for an eruption to take place being above a weak point in the Earth’s crust, rather than the area where it is causing an uplift. However, they said there was disagreement among geologists about the nature of the eruption were it to occur.

Using radar imagery taken over the weekend, the Icelandic Met Office said there had been a “significant crustal uplift” near Svartsengi, a geothermal hotspot on a southwestern cape on the island, near the capital Reykjavik, which was “indicative of a deep inflation” taking place. The ground has moved upwards by as much as three centimeters.

“Initially, the uplift sign was influenced by the formation of the intrusion, but now the dominance of deep magma recharge is apparent,” it said.

According to Andrew Hooper, a geophysicist at the University of Leeds in the U.K., who specializes in radar imaging of ground deformations, a magma intrusion is molten rock which moves upwards from deep within the Earth’s mantle and pushes into the crust.

“At Svartsengi, there have been two types of intrusion—in the first type, the magma spread out horizontally at about three miles depth beneath Svartsengi,” he told Newsweek. “This happened several times in the last few years and caused the ground to uplift above it each time. This was happening up until Friday, November 10.”

However, he added: “In the other type of intrusion, magma moved very rapidly upwards and laterally, forming a vertical sheet. This is what commenced on Friday, November 10, and is continuing at a decreased rate until today.

“This lies to the east of Svartsengi and runs beneath the town of Grindavik, with magma probably having reached to within half a mile from the surface or less.”

While the uplift is occurring in an area on the cape with a diameter of approximately 10 kilometers (six miles) to the north of Grindavik, the vertical intrusion has appeared along a straight line running southwest to northeast immediately next to the town.

Haraldur Sigurdsson, an Icelandic volcanologist and an emeritus professor of geophysics at the University of Rhode Island, explained that at the start of November, the North American tectonic plate had shifted away from the Eurasian plate by four or five centimeters, compared to its “rather slow” usual movement of around a centimeter a year.

“This sudden shift is large and reminds us that plate motions are episodic, sporadic, [that occur] in fits and jumps,” he told Newsweek, leading to what he described as an “important plate motion episode” in Iceland.

The rift between the North American and Eurasian plates sits underneath Iceland—which is thought to have been formed by volcanic activity 16-18 million years ago—with the two plates slowly moving apart from one another. A sudden shift would have created a wider gap and allowed magma to course upwards, creating the swell in the Earth’s crust.

Hooper said the magma causing the current uplift would be “building new pressure, which could eventually lead to a new rapid vertical intrusion, possibly one that breaches the surface and erupts.”

‘Voluminous’ Eruption or ‘Overreacting’?

“People in Iceland are hypersensitive to volcanic eruptions in the wake of plate motions, so the nation is nervously waiting for or expecting an eruption,” Sigurdsson said.

He argued that the authorities in Iceland had taken “rather draconian measures” by evacuating Grindavik’s 3,400 residents and closing roads to traffic nearby, but said: “I guess they work on the principle of better safe than sorry, but the restrictions have shut down the town’s flourishing fishing industry, and caused hardships.”

“Iceland is relatively wealthy and the nation can afford to support a dislocated population for a while,” he added. “The same thing happened in the Westman Islands, south of Iceland, in 1973, when an entire population evacuated an erupting island. Not everyone returned, but it is again a flourishing fishing town today.”

The Icelandic Met Office has said there was a “significant likelihood” of an eruption above the vertical magma intrusion. In its most recent update, it noted: “The clear sign of crustal uplift in Svartsengi region does not change the likelihood of an eruption from the magma intrusion,” as “the Earth’s crust over the magma intrusion is much weaker than the crust over the uplift region.”

The last time a major eruption occurred in Iceland was in 2010, when the Eyjafjallajokull volcano erupted several times causing a massive ash cloud to spread over Europe and North America, leading to severe disruption to air travel.

Hooper said the recent data showed the initial, horizonal form of magma intrusion had restarted, but at a faster rate than before. “This does not indicate that an eruption is more imminent,” he said. “But as before, an eruption is still possible with little warning.”

The volcanologist agreed with the Icelandic Met Office that “an eruption is not likely to happen from the uplifting region, however, but is more likely from the area above the vertical sheet that has intruded to a shallow depth.”

He added: “This would likely cause an eruption similar in style to those seen in recent years from Fagrdalsfjall, but possibly more voluminous.” Fagrdalsfjall is a volcano that sits in the same region of Iceland as Grindavik, and has erupted several times since March 2021 after being dormant for over 800 years, causing significant lava flows.

“I personally am not of the opinion that an important volcanic eruption is about to take place, and I think that the authorities are overreacting,” Sigurdsson said. “But if the authorities can carry out and maintain a successful evacuation for several months, then they are playing it safe and that is important.”