Residents in southwestern Iceland left their homes on the weekend after increasing concern about a potential volcanic eruption caused civil defense authorities to declare a state of emergency in the region. Earlier, the Blue Lagoon geothermal spa – one of Iceland’s biggest tourist attractions – closed temporarily as a swarm of earthquakes put the island nation’s most populated region on alert.

Guests rushed to leave the spa’s hotels in the early hours of Thursday, after they were rattled awake shortly before 1 a.m. by a magnitude 4.8 quake, the strongest to hit the region since the recent wave of seismic activity began on Oct. 25.

On Saturday, police decided to evacuate Grindavik after recent seismic activity in the area moved south toward the town and monitoring indicated that a corridor of magma, or semi-molten rock, now extends under the community, Iceland’s Meteorological Office said. The town of 3,400 is on the Reykjanes Peninsula, about 50 km southwest of the capital, Reykjavik.

“At this stage, it is not possible to determine exactly whether and where magma might reach the surface,” the Meteorological Office said.

Authorities also raised their aviation alert to orange, indicating an increased risk of a volcanic eruption. Volcanic eruptions pose a serious hazard to aviation because they can spew highly abrasive ash high into the atmosphere, where it can cause jet engines to fail, damage flight control systems and reduce visibility.

Iceland, which sits above a volcanic hotspot in the North Atlantic, averages an eruption every four to five years. The most disruptive in recent times was the 2010 eruption of the Eyjafjallajokull volcano, which spewed huge clouds of ash into the atmosphere and led to widespread airspace closures over Europe. The eruption caused widespread disruption to air travel between Europe and North America, costing airlines an estimated $3 billion as they canceled more than 100,000 flights.

The present evacuation comes after the region was shaken by hundreds of small earthquakes every day for more than two weeks as scientists monitor a buildup of magma some 5 km. underground.

The Reykjanes Peninsula on Iceland’s southwestern coast includes a volcanic system that has erupted three times since 2021, after being dormant for 800 years.
Previous eruptions occurred in remote valleys, without causing damage. While scientists say that is the likely outcome of the current activity, the magma storage chamber currently building up again could erupt less than 3 km. from the Blue Lagoon.
In the worst-case scenario, lava would threaten the town of Grindavík and the Blue Lagoon, along with the pipelines channeling hot water to thousands of homes that are heated with geothermal energy.

“We need to be prepared for the worst,” volcanologist Thorvaldur Thordarson said. “Magnitude 5 earthquakes, such as the one last night, are known to precede eruptions.”

The Blue Lagoon, where tourists bask in pools of seawater naturally heated deep underground, said it will remain closed until Nov. 16.