NEW YORK and LONDON -- A volcano began erupting on Monday in Iceland, the country's meteorological office said, after weeks of anticipation during which tens of thousands of earthquakes rumbled the southwestern coast.
"An eruption has started north of Grindavík," the Icelandic Met Office said in an alert on its website. "It can be seen on webcams and seems to be located close to Hagafell, about 3 km [about 1.8 miles] north of Grindavík."
An "earthquake swarm" started around 9 p.m. local time and the eruption began at 10:17 p.m., the office said. The intensity of the eruption began to decrease within hours, officials said in an update about four hours after later.
"The fact that the activity is decreasing already is not an indication of how long the eruption will last, but rather that the eruption is reaching a state of equilibrium," the Met said.
The affected area near Grindavík remained closed off by the country's Civil Defense, President Guni Th. Jóhannesson said on social media early Tuesday.
"We now wait to see what the forces of nature have in store," he said. "We are prepared and remain vigilant."
Iceland's Meteorological Office said the eruption was located on "the dyke intrusion that formed in November." The eruption fissure, as the Met Office called it, began expanding southward, with the southern end of it near Sundhnúkur.
Icelandic weather officials scheduled a meeting with scientists on Tuesday morning to evaluate what had happened overnight, according to the Met.
It estimated the lava discharge from the fissure to be "hundreds of cubic metres per second," adding that the biggest lava fountains were on the northern end. The lava was spreading laterally, the office said.
Local weather officials had warned in November there was a "significant likelihood" of a volcanic eruption. More than 20,000 quakes have shaken the area since late October, officials have said.
At the time, officials declared a state of emergency near the Mount Fagradalsfjall volcano on the sparsely populated Reykjanes Peninsula.
About 3,700 residents of Grindavík, a nearby fishing town, began evacuating on Nov. 10, according to the Department of Civil Protection and Emergency Management. The evacuation was successful, Bjarni Benediktsson, the minister of foreign affairs, said at the time.