A widely anticipated eruption on Iceland's Reykjanes Peninsula occurred after more than a month of seismic activity, with one volcanologist saying that lava fountains pouring out of the ground reached 656 feet into the air.
A vertical intrusion of magma that had been building since November 10 reached the surface of the Earth's crust at 10:17 p.m. local time (5:17 p.m. ET) on Monday, about 1.7 miles to the northeast of the coastal fishing town of Grindavik. The town was evacuated earlier and has been surrounded by earth walls to divert lava flows.
The Icelandic Meteorological Office said that the fissure appeared between the Hagafell and Stóra Skógfell mountains, where it had previously predicted an eruption was most likely, and that it was around 2.5 miles long. The eruption was preceded by a swarm of earthquakes that began at 9 p.m. the same evening.
Officials said the discharge rate in the first two hours of the eruption was between 100 and 200 cubic meters per second, which was "many times more than in previous eruptions on the Reykjanes Peninsula in recent years." They noted that the largest lava fountains were toward the northern end of the fissure.
Haraldur Sigurdsson, an Icelandic volcanologist and emeritus professor of geophysics at the University of Rhode Island, told Newsweek: "The fountains of magma were truly spectacular, reaching heights of 100 to 200 meters."
He said he thought the population of Grindavik "should be allowed to return to their homes now," as the eruption has slowed down from the initial burst and could be over by the end of the month.
"There are a thousand reasons for allowing the population to return quickly, both economical, social and emotional," Sigurdsson said. "They should be allowed home for Christmas."
However, Andrew Hooper, a geophysicist at the U.K.'s University of Leeds who specializes in ground deformations, told Newsweek it was "too soon to say how long it might last."
The Icelandic Meteorological Office confirmed that the intensity of the eruption was decreasing as of 3 a.m. local time. But it said that this "is not an indication of how long the eruption will last but rather that the eruption is reaching a state of equilibrium," and had been "observed at the beginning of all eruptions on the Reykjanes Peninsula in recent years."
It is believed that the vertical intrusion is connected to and being fed by a horizontal reservoir of magma around 6 miles in diameter that has been pushing the ground up by around a centimeter (nearly half an inch) a day under Svartsengi, a nearby geothermal power plant.
The area surrounding Svartsengi has been the site of several horizontal magma intrusions in recent years, but the Icelandic Meteorological Office said that since a burst of seismic activity on November 10, there has been "significant crustal uplift" in the region.
The office previously expressed uncertainty as to when and where an eruption may occur after a decline in the number and severity of earthquakes around the vertical magma dike—estimated to be around 9.3 miles long under the surface.
The area of eruption runs close to Svartsengi, and the Icelandic office said lava was spreading from the fissure laterally. However, there is elevated ground between the power plant and the fissure, and Icelandic authorities have constructed protective walls and channels around the power plant.
Hooper said the vertical intrusion "is currently no longer propagating and, as things stand, lava is not flowing towards Grindavik or the Svartsengi power plant, which is obviously great news."
He added: "How far the lava travels depends on many factors, but [it is] likely to be up to a few kilometers."
"The lava is spreading over an uninhabited region and does not threaten lives or property at this time," Sigurdsson said. "The eruption has much diminished and the flow rate has decreased from over 100 cubic meters per second initially to less than 10 cubic meters per second." He sees this as a sign that "the eruption will be over soon."
Gudni Thorlacius Johannesson, the president of Iceland, confirmed in a social media post that authorities had closed off the area of the eruption and were prioritizing the protection of lives and infrastructure. "We now wait to see what the forces of nature have in store," he said.
A sudden shift in the North American tectonic plate away from the Eurasian plate is thought to have allowed magma to suddenly push upward through a rift that runs between them under Iceland, creating the swell in the Earth's crust.
Sigurdsson previously told Newsweek that after a dormant period, the volcanic activity could mark the start of a new episode of "rifting and volcanism" on the Reykjanes Peninsula. Much of Iceland's infrastructure—including the capital, Reykjavík—is located in the region, he said.
On Tuesday, he described the eruption as "a surprise for many" but said that "it may signal the beginning of a more quiet period in this part of Iceland, for a while at least," as "the pressure is off and the magma found its way to the surface."
Update 12/19/23, 1:40 p.m. ET: This article was updated to include comments from Icelandic volcanologist Haraldur Sigurdsson.
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