Iceland’s second-largest volcano may be about to wake up after a near-decade-long slumber, following a “swarm” of seismic activity in the area this week.

Approximately 130 earthquakes were recorded at Bárðarbunga, Iceland’s second-largest volcano, on Tuesday, according to the Icelandic Met Office (IMO). The swarm is the most significant since the sleeping giant last erupted back in 2014.

In response to the swarm, the aviation color code was raised to Yellow, meaning the volcano is experiencing signs of elevated unrest above known background levels. However, this is still two levels lower than the maximum, Red level.

Newsweek contacted the IMO via its website for further comment.

Why This Matters

Bárðarbunga is Iceland’s second-tallest volcano and is “unusually large,” the IMO said in its update.

If an eruption is imminent, it could impact air quality in Iceland and beyond, as well as air travel.

What to Know

Approximately 130 earthquakes were reported on Tuesday, marking the most significant uptick in activity since Bárðarbunga last erupted in 2014.

Of those, the largest earthquake had a magnitude of 5.1, while 17 measured in at 3 or higher.

According to the IMO, the activity is consistent with increased pressure caused by magma accumulation beneath the layer of ice that blankets the volcano. This accumulation has been ongoing since the last eruption ended in 2015.

Geodetic positioning data adds to the evidence that an eruption could be on its way, with an increased level of inflation being recorded at the volcano.

However, it is difficult to predict exactly what may happen—volcanic eruptions are notoriously hard to forecast.

“Bárðarbunga is unique in that it is an unusually large volcanic system, partly covered by a glacier, and several scenarios are possible,” the IMO said.

One possible scenario is an eruption outside of the volcano’s caldera—the circular depression that forms a crater at a volcanic summit—as happened in the 2014 eruption. An eruption such as this might cause extensive lava flows but is unlikely to send significant volumes of ash into the air.

If the eruption occurs in the caldera itself, it could be more explosive. Glacial material could be vaporised in such a scenario, leading to ash emissions that could disrupt air travel. A glacial outburst flood could also result from such an eruption.

Bárðarbunga is located in a remote part of Iceland, meaning any eruption scenario is unlikely to pose a significant threat to large communities in the country.

What People Are Saying

David Pyle, a professor of Earth sciences at the University of Oxford, U.K., told Newsweek: “The earthquakes are clearly associated at depth with the ring-shaped fracture system that forms the large crater, or caldera, of Bárðarbunga volcano.

“While the pulse of seismic activity was the largest seen here since the last eruption in 2014, the event lasted just a few hours. It is a reminder that the Bardarbunga volcanic system is active, and there are several possible explanations for the earthquakes—most likely that there is some magma moving at depth.”

Tamsin Mather, a professor of Earth sciences at the University of Oxford, U.K., told Newsweek: “This probably means that magma is building up again and has been doing so since 2015.

“I don’t think anyone is suggesting at the moment that there is a risk of something happening like Eyjafjallajökull in 2010, which wasn’t a particularly large-scale eruption—it just produced a lot of fine ash and the weather pattern was such that it blew in a most inconvenient direction for air traffic.

“We would say that is unlikely until we start to see more about what type of magma is down there and where it’s going to erupt, but I don’t think it’s the most likely scenario.”

What Happens Next

The IMO is continuing to monitor the situation closely. However, it is too early to determine when and if a significant eruption may occur.

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