In 2010, ash spewed into the atmosphere by the volcano beneath Iceland's Eyjafjallajökull glacier grounded European air traffic for days (and, partially, for weeks). As reported by The Guardian, a series of similarly situated earthquakes may herald a similar ash-ejecting erruption, and the country has raised its volcano risk to its second-most-severe rating (orange). From the article: Iceland met office seismologist Martin Hensch said the risk of any disruptive ash cloud similar to the one in 2010 would depend on how high any ash would be thrown, how much there would be and how fine-grained it would be. Bardarbunga is Iceland's largest volcanic system, located under the ice cap of the Vatnajokull glacier in the southeast of Iceland. It is in a different range to Eyjafjallajokull. The met office said in a statement it measured the strongest earthquake in the region since 1996 early on Monday and it now had strong indications of ongoing magma movement. "As evidence of magma movement shallower than 10km implies increased potential of a volcanic eruption, the Bardarbunga aviation colour code has been changed to orange," it said. "Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood and ash emission." ... Hensch said the biggest risk in Iceland itself was from flood waves from any eruption under the glacier. He said the area of Iceland mainly at risk of flooding was mostly uninhabited but that roads in the area had been closed.