The volcano that erupted under the Eyjafjallajökull glacier in Iceland Thursday blasted ash miles into the air, disrupting air traffic across Northern Europe and beyond.

Here is information on volcanic ash:

What produced the ash?

Volcanic activity and earthquakes are common in Iceland, which sits on the mid-Atlantic Ridge - a 10,000-mile seam across the floor of the Atlantic where the North American and Eurasian tectonic plates are moving apart.

This volcano last erupted in 1821.

What is the ash made of?

Volcanic ash is hard and abrasive, tiny particles of exploded rock and glass. As magma rises inside the earth, bubbles of gas produce explosive pressure that shatters the molten material into fragments, said Bill Burton of the U.S. Geological Survey's Volcano Hazards Program.

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Where is the ash cloud?

The plume as of late Thursday was between 15,000 and 33,000 feet above sea level, at least 50 miles wide and heading south and east with the prevailing winds. It took about nine hours for the plume to reach Norway, Burton said.

 

How are volcanic plumes tracked?

Nine volcanic ash advisory centers scattered across the globe follow ash clouds' progress, using satellite images and reports from pilots and seismologists. Researchers use wind models and look at altitude and velocity to predict where the ash may go.

 

Will the cloud travel here?

Unlikely, Burton said. It would have to travel east around the globe. Such global impact is typically only seen in major eruptions, such as Krakatau.