FILE This is a Saturday May 8 2010 file image taken from video of a column of ash rising from Iceland's Eyjafjallajokul volcano. (Anonymous/AP)

Iceland’s Bardarbunga volcano began erupting Saturday under the ice of Europe’s largest glacier, prompting the country to close the airspace over the volcano.

Thousands of small earthquakes have rattled the volcano, deep beneath the Vatnajokull glacier, in the past week. Seismic data indicated that magma from it was melting ice beneath the glacier’s Dyngjujokull ice cap, Meteorological Office vulcanologist Melissa Pfeffer said.

The remote area, 200 miles east of the capital, Reykjavik, is uninhabited.

The Civil Protection Department said scientists flew over the ice cap Saturday afternoon but saw no visible signs of the eruption on the surface.

Still, authorities raised the country’s aviation alert to red — the highest level on a five-point scale — indicating the threat of “significant emission of ash into the atmosphere.”

A warning sign blocks the road to Bardarbunga volcano, some 20 kilometres (12.5 miles) away, in the north-west region of the Vatnajokull glacier August 19, 2014. (Stringer/Reuters)

Icelandic authorities declared a no-fly zone of 100 by 140 nautical miles around the eruption as a precaution but did not shut down airspace over most of the island nation in the North Atlantic.

“All airports are open, and flights are on schedule,” said spokeswoman Olof Baldursdottir.

An eruption of Iceland’s Eyjafjallajokul volcano in 2010 produced an ash cloud that caused a week of international aviation chaos, with about 100,000 flights canceled.

Pfeffer said it was not clear when, or whether, the eruption would melt through the 330-to-1,300-foot-thick ice and fling steam and ash into the air. She said it could take up to a day for the ice to melt — or the eruption might remain contained beneath the glacier.

Scientists were monitoring a hydrological station downstream from the volcano for flooding, a common result of volcanic eruptions in Iceland.

Pfeffer said the amount of ash produced by the new eruption will depend on the thickness of the ice.

“The thicker the ice, the more water there is, the more explosive it will be and the more ash-rich the eruption will be,” she said.

Iceland sits on a volcanic hot spot in the Atlantic’s mid-oceanic ridge. Eruptions occur frequently, triggered when Earth’s plates move and when magma from deep underground pushes its way to the surface.