The last time Iceland's Eyjafjallajokull volcano blew, the eruption lasted more than a year, from December 1821 until January 1823, reports Sally Sennert, a geologist at the Smithsonian Institution.

"This seems similar to what's happening now," she says.

The volcano is erupting small, jagged pieces of rocks, minerals and volcanic glass the size of sand and silt into the atmosphere, according to the U.S. Geological Survey. This volcanic ash can even be as small as 1/25,000th of an inch across.

Volcanic ash is formed during explosive volcanic eruptions. Once in the air, the wind can blow these tiny ash particles tens to thousands of miles away from the volcano. Life-threatening and costly damages can occur to aircraft that fly through an eruption cloud, reports the geological survey.

"Silica in the ash gets into the engine and heats up and melts, which causes the engines to stop," says Sennert.

Based on reported damages from ash encounters, the hazard posed to aircraft can extend more than 3,000 miles from an erupting volcano. (Click here for a map of the ash zone over Europe).

Fortunately for the USA, Sennert says the wind direction is such that the ash cloud is traveling east-southeast, toward Europe and away from the USA.

However, as Science Fair noted previously, the Eyjafjallajokull volcano isn't necessarily the main problem. It's Katla, Iceland's noisier neighbor, that's the concern. If lava flowing from Eyjafjallajokull melts the glaciers that hold down the top of Katla, then Katla could blow its top, pumping gigantic amounts of ash into the atmosphere.

The potential eruption of Iceland's volcano Katla could send the world, including the USA, into an extended deep freeze.

"There's no telling how long the eruptions could last," says Sennert about the Eyjafjallajokull volcano."These explosions could go on for some time."

By Doyle Rice