Icelandic authorities declared a state of emergency and evacuated a town of about 4,000 people Saturday after hundreds of earthquakes were detected overnight, signaling an increased likelihood of a volcano erupting in the country’s southwestern Reykjanes Peninsula.
The Icelandic Meteorological Office, the country’s weather service, said it was not possible to say when and where magma would reach the surface of the town of Grindavik, but it warned that “the likelihood of a volcanic eruption occurring in the near future is deemed considerable.”
Residents of Grindavik were warned that they would probably not be able to return home for days.
Authorities also raised the aviation alert to orange with the increased chance of eruption, which could pose a risk to aviation if ash spewed into the sky, affecting aircraft.
The enhanced seismic activity measured near Sundhnjukagigar, north of Grindavik, came two days after thousands of other earthquakes rattled the region, prompting officials to close the Blue Lagoon, a popular tourist destination known for its geothermal spas.
That spell of seismic activity led scientists to believe that an eruption might be imminent.
While the evacuation orders were not an “emergency evacuation,” which would require leaving the area within 30 minutes, officials at a news conference Saturday said that residents should still leave within two or three hours, The Reykavik Grapevine, a local news outlet, reported.
The weather service said that “scientists are meeting regularly to interpret the data and update the latest models and hazard assessments.”
Local news outlets and writers have posted images of roads cracked by the seismic activity as residents fled the area and contended with waves of shocks.
Alda Sigmundsdottir, a writer in Iceland, said on Facebook that while she was writing a post, she was “shaken by an earthquake.”
Magma under the area has grown much closer to the surface in recent days, officials said.
On Wednesday, it was a little more than 3 miles underground, but Saturday, the shallowest depth was roughly 1 mile.
There is a long history of volcanic activity in Iceland, a country of fewer than 400,000 people and home to about 130 volcanoes, most of which are active.
The country straddles two tectonic plates, which are themselves divided by an undersea mountain chain that oozes molten hot rock, or magma. Earthquakes occur when the magma pushes through the plates.
Iceland is also above a “hot spot,” a place with “abnormally high magma activity,” according to the country’s tourism website, which notes that other such places include Yellowstone National Park and Hawaii.
Volcano eruptions in Iceland have at times had devastating effects.
In 2010, the eruption of the Eyjafjallajokull volcano spewed so much ash that it grounded flights across parts of Europe for weeks.
This article originally appeared in The New York Times.