Thousands of earthquakes have been caused by a massive buildup of magma in a nine-mile fissure.

The fissure is located about 3.5 kilometers northwest of Grindavik, a town of 4,000 people on the Reykjanes Peninsula that has been evacuated.

What are the chances of an eruption?

Iceland’s Meteorological Office said Wednesday that “the probability of an eruption is still considered high.”

Vidir Reynisson, head of Iceland’s Civil Protection and Emergency Management agency, said experts are “really worried about all the houses and infrastructure in the area.”

John Smellie, a volcanologist at the University of Leicester in the United Kingdom, said lava flows “relatively slowly, and people can usually at least move away or run away from it.”

He said this means deaths are unlikely.

The eruption could be more violent if it passes through ice or water.

If it occurs at the southern end of the fissure, which is underwater, it could cause ash clouds that would affect flights at Iceland’s international airport.

Different from the 2010 Eyjafjallajokull eruption?

No eruption is expected to have as much impact as that of the Eyjafjallajokull volcano in 2010.

That eruption spewed huge amounts of ash into the atmosphere, forcing the cancellation of some 100,000 flights and stranding more than 10 million travelers.

It exploded through 200 meters of ice, making it “very violent,” Smellie said.

The interaction with water created finer ash particles that would later move across Europe.

The latest eruption threat is a “completely different situation,” Smellie said.

Marc Reichow, a geochemist at Leicester, said: “It is unlikely to happen this time as there is not a substantial amount of ice in the area where an eruption is expected to occur.”