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A car is seen driving through the ash from the volcano eruption under the Eyjafjallajokull glacier in Iceland, Friday April 16, 2010.

A car drives through ash fallen from the Eyjafjallajökull volcano plume on April 16, 2010.

Photograph by Omarr Oskarsson, AP

Brian Handwerk

for National Geographic News

Published April 16, 2010

Iceland's Eyjafjallajökull volcano continued to erupt on Friday, creating an enormous ash plume visible from space that's been causing major problems here on Earth. (See pictures of the Iceland volcano's ash plume.)

In addition to scores of canceled flights, the World Health Organization has warned people across Europe to stay indoors or use masks when the ash begins to fall.

Volcanic ash is made up of tiny pieces of glassy sand and dust produced when explosive eruptions demolish solid rock or spray lava into the sky, where it solidifies before falling.

Inhaling these particulates can cause irritation of the eyes, nose, and throat. Finer particles can penetrate deep into the lungs and cause breathing problems, particularly among those with respiratory issues like asthma or emphysema.

But other scientists believe that ash fall from Eyjafjallajökull will be too limited and scattered to have much impact outside of Iceland. (See pictures of the current Iceland volcano eruption.)

Instead, the drifting plume presents a golden opportunity to learn more about wind currents and chemical reactions in our atmosphere.

Major Ash Yet to Fall in Europe

To date, there has been noticeable ash fall just east of the volcano, with ash completely covering the ground out to about 38 miles (60 kilometers), said Icelandic volcanologist Thorvaldur Thordarson.

"Locally, close to the eruption, it can cause health problems. But I seriously doubt that it will have a significant effect beyond that area," said Thordarson, of the University of Edinburgh in Scotland.

In fact, major amounts of ash have yet to fall in the U.K. or on the European continent, and they may not do so at all. That's because the plume continues to be held aloft by air currents, and by the time particles fall, the cloud may have dispersed over a wider area.

In general, the size of the plume and how far ash gets hurled aloft play major roles in determining how much ash falls and where it lands, Thordarson said.

Daily wind and weather patterns also guide how far a plume goes and how long it stays aloft.

Heavier ash fall "probably should have happened by now, given that the cloud has been over Europe for about 24 hours," said Tina Neal, a volcanologist at the Alaska Volcano Observatory in Anchorage.

"The particles will eventually settle out, but it may take days or weeks, and at this point it doesn't seem like it's going to [accumulate] that much in continental Europe, in terms of the size of this eruption," Neal said.

"But we have to watch, because if the eruption intensifies, [so may] the ash fall."

Iceland Plume a Boon to Science

Meanwhile, the plume is being welcomed by scientists studying volcanoes and how their eruptions impact Earth.

During an eruption, remote sensing and satellite imagery can help identify a plume's composition and levels of volcanic gasses. That information could help to lessen airline troubles like the situation now impacting travel to and from Europe.

(See aerial pictures taken in March of the erupting Iceland volcano.)

"The vexing thing for aviation is that we can't tell them what's in the clouds, so they have to avoid all of them," Neal said. "If we can get better at characterizing the clouds, maybe we can get better at telling them what's safe and what isn't."

Ash plumes can also serve as ideal "tracers" for visualizing the movements of air currents. In that respect, an eruption can help scientists understand much more about the processes of atmospheric circulation that help determine Earth's weather.

"We don't know a lot about how air moves at these altitudes," Neal said, referring to the Eyjafjallajökull plume, which is now drifting at roughly 30,000 feet (9,144 meters).

Chemical analysis via satellite data can also reveal how ash and gas clouds interact with the atmosphere and whether the particles in the plume will linger, dimming the skies for extended periods.

The current eruption probably isn't big enough to cause global climate changes, at least not at this point, Neal said. (See "Volcanic Activity Triggered Deadly Prehistoric Warming.")

But observing how chemical changes work in the plume can help scientists model the ways in which truly massive eruptions might have impacted Earth's climate in the past—and how they could do so again.

Ash May Be Toxic to Iceland Animals

In Iceland itself, Eyjafjallajokull's impacts are being felt far more immediately. (See "Iceland Volcano Erupts Under Glacier, Triggers Floods.")

One danger is to livestock health: Depending on the different types of magma involved, some volcanic eruptions send out fluorine aerosols, which become attached to ash particles.

If animals feed on grasses covered with fluorine-filled ash, they can contract fluorosis, a fatal bone disease. (See a picture of a calf wearing a face mask after a Peruvian volcanic eruption.)

Fluorine levels in the current eruption's dry ash are high enough that they could prove toxic to grazing livestock in some areas, the University of Edinburgh's Thordarson reports.

Fortunately, most Icelandic livestock is quartered indoors for the season, and the animals are mostly eating dry hay. But farmers are being warned that the ash could cause problems should eruptions occur when warmer weather returns.

Based on historical eruptions of Eyjafjallajökull, experts say the volcano could erupt for months or even years.

While it's unlikely the plume will be disruptive during that entire time, some problems could persist or even increase if the eruption grows or is joined by another from the nearby volcano Katla.

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