LONDON – Volcanoes in southwestern Iceland have been quiet for 800 years, but the period of rest may soon be over: More than 18,000 earthquakes have shaken the area in just over a week, leading scientists to believe that an eruption could be imminent.
Geophysicists and volcanologists say the quakes are the culmination of more than a year of intense seismic activity, and although most of the tremors have lasted a few seconds, with light shaking, they have rattled residents in the capital, Reykjavik, just 32 km north of the Reykjanes Peninsula where they have occurred.
“People in Reykjavik are waking up with an earthquake, others go to sleep with an earthquake,” said Thorvaldur Thordarson, a professor of volcanology at the University of Iceland. “There’s a lot of them, and that worries people, but there’s nothing to worry about, the world is not going to collapse.”
Earthquakes are common in Iceland because it straddles two of the Earth’s tectonic plates, the North American and Eurasian, which are divided by an undersea mountain chain, the Mid-Atlantic Ridge. The ridge oozes molten hot rock, or magma, from deeper in the Earth, forcing the plates to spread apart and causing quakes on the island.
Most of the quakes, however, are small and occur far from Reykjavik and the surrounding areas, where a majority of Iceland’s 368,000 residents live. Dr. Pall Einarsson, a professor emeritus of geophysics at the University of Iceland, said what usually fascinated scientists was now riveting the tiny nation.
“Never in my lifetime have I experienced so many earthquakes,” Einarsson said. “We’re talking about feeling several of them every day.”
The current earthquake swarm started Feb. 24 with a 5.7-magnitude quake, the largest to date, and thousands of others have since followed. On Wednesday, more than 2,500 tremors were measured by the Icelandic Meteorological Office, followed by 800 more in the first hours of Thursday.
Geophysicists and volcanologists say the seismic activity on the island has intensified since December 2019. In October 2020, Prime Minister Katrin Jakobsdottir had to briefly interrupt herself during a live interview as an earthquake was felt in the country. (“Well, this is Iceland,” Jakobsdottir said, before resuming.)
Similar tremors have been observed before volcanic eruptions in the past, and the Icelandic Meteorological Office said that magma movements were a likely cause for the continuing activity. The agency has warned that an eruption could occur within days or weeks.
“The two tectonic plates are moving away from each other, and that movement has created the conditions for magma to come to the surface,” said Freysteinn Sigmundsson, a research professor of geophysics at the University of Iceland.
Einarsson said that out of the five volcanoes in the Reykjanes area, magma movement had been observed near at least three of them since the seismic episode began in December 2019. “We may be entering a new active period in the peninsula,” he added. “There seems to be food for some eruption.”
Iceland has about 30 active volcanoes, but volcanologists say an eruption in Reykjanes won’t threaten inhabited areas on the peninsula. “We’re talking about an effusive eruption, rather than explosive,” said Sigmundsson, explaining that the lava would likely bubble out with little explosive force.
He added that any activity is unlikely to be as disruptive as the eruption that occurred in 2010, when another volcano in Iceland released a plume of ash so vast that it caused one of the most significant air-traffic interruptions in decades, stranding millions of passengers in Europe, some for weeks.
The meteorological office said the volcanic activity could occur near Fagradalsfjall, 32 km south of Reykjavik, or near the Keilir mountain close by. Hundreds of volcano enthusiasts have been riveted to live cameras in the area, and a website asking “Has there been an eruption yet?” has kept them up-to-date. (It still read “Nei” — No — as of Thursday afternoon, but a playlist on the website helped with the wait.)
The meteorological office said that among possible scenarios, the ongoing seismic activities could decrease in the coming days or weeks, but the peninsula could also face more earthquakes, up to magnitude 6.5.
Meanwhile, volcanologists are readying themselves for what could be decades of increased activity.
“Pulses of volcanic activity in the area come roughly every 800 years,” Thordarson said about the last eruptions in Reykjanes, which spanned from the 11th to the 13th century. “It looks like we are on time.”
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