Magma is on the move in Iceland. But is it moving up?

This is the question facing geologists as they contemplate a potential eruption of a massive volcano under the island nation’s largest glacier—a volcano that dwarfs Eyjafjallajokull, whose 2010 eruption famously disrupted air travel for days, stranding millions of travelers.

Iceland is not nicknamed the Land of Fire and Ice for nothing. Bárðarbunga, or Bardarbunga as it’s spelled in English, is a massive volcano located under Iceland’s Vatnajökull glacier near the center of the country. The entire volcanic system is 120 miles long and 16 miles wide, and the mountain itself is 6,591 feet above sea level.

For the past several days the region has been rocked by more than 1,000 earthquakes, an indication that magma is restless below the Earth’s surface, experts say. This could very well be the prelude to a full-scale eruption, and an area to the north of the glacier has been evacuated as a precaution in case of flooding.

The earthquake swarm began on Saturday August 16 and rocked the region with more than 1,000 temblors that first weekend. With a 4.7 magnitude earthquake hitting 2.5 miles southeast of Bárðarbunga early on August 22, the activity seems to be escalating.

“It’s the biggest earthquake to have hit in the area since the current seismic activity began there last Saturday,” reported the Iceland Review. “More than 2,100 earthquakes have been picked up by sensors in Vatnajökull in the past 48 hours. The seismic activity continues, although the area is rather quiet at the moment.”

For now, relative calm prevails.

“Intense earthquake swarm continues at Barðarbunga,” said the Icelandic Met Office on its website on August 22. “Presently there are no signs of magma moving to the surface.”

That could change quickly, however, and the alert level has been upgraded to orange, the second one below full-scale eruption. Many experts are speculating about what an eruption could mean, ranging from spewed poisonous gas to disrupted air travel.

The Daily Kos compared its potential to the eruption of the massive Laki in the 1700s, which changed weather worldwide.

“Laki emitted 8 million tons of hydrogen fluoride—normally a trace volcanic gas,” the Daily Kos reported. “These gasses created the ‘Laki Haze’ across Europe. In Iceland, the consequences were most severe—a quarter of the population starved or died of fluoride poisoning, and most of the livestock died. Denmark considered evacuating the entire island.”

Even the Daily Kos said, though, that such a stark outcome is not necessarily probable. Just because magma is on the move does not mean it will reach the surface and explode out of the ice. But it could. And that could cause glacial flooding in Iceland, catastrophic level unknown. Laki was but Barðárbunga’s “little sister,” the Daily Kos said, though Slate noted that it was not situated under a glacier as Bardarbunga is.

At the very least it could disrupt air travel, as CNN reported. When Eyjafjallajokull erupted in 2010 it sent “glasslike fragments high into European airspace,” the news network reported. Flights were grounded for six days, stranding millions of passengers, who then had to wait even longer for carriers to deploy crews and planes once they were back in the air. But many aviation experts said European authorities overreacted, and changes made since then could reduce disruption in the case of a Bardarbunga incident, CNN said. That includes better monitoring of ash clouds, more coordination between countries, and a recognition that airlines, not governments or countries, should decide whether to fly.

As it happens, more than 200 geologists and geochemical engineers are on hand this weekend attending the International Carbon Capture conference in Reykjavik.

“The timing is unintentional,” said conference press officer Thomas Parkhill in a note to reporters, while acknowledging that it is fortuitous. “Of course, the timing of the conference means that there will be a concentration of geological expertise in Reykjavik, in advance of the possible eruption of the Bardarbunga volcano. Some of those attending will have relevant experience of Icelandic geology.”

The one thing that experts can agree on is that the situation bears monitoring, and that what happens will be anybody’s guess.

“It is impossible to predict how the processes will develop,” wrote geologist and onetime Iceland presidential candidate Ari Trausti Guðmundsson in a blog post, as reported by Slate.