Good and bad news about new Iceland volcano eruption

Reuters reported a couple hours ago that the eruption, which happened yesterday, is intensifying and showing no signs of abating. The New York Times reported a half hour ago that the eruption isn't all that powerful (when compared to something like the 1991 eruption in the Philippines.) But there is also bad news:

Eruption Wasn’t That Powerful, but Effects May Linger
By HENRY FOUNTAIN, April 15, 2010

The Icelandic volcanic eruption that disrupted air travel in Europe on Thursday was not a particularly powerful one, experts said, but they cautioned that its effects — both on travel and the regional climate — may linger.

Bill Burton, associate director of the U.S. Geological Survey’s volcano hazards program, said the current eruption under the Eyjafjallajokull glacier bore similarities to the last eruption there, in 1821. “We seem to be reprising that episode again,” he said.

That eruption continued, on and off, until 1823. While no one can predict how long this one may last, Dr. Burton said, in vulcanology, “The past is the key to the present.”

He added, “So if the other eruption lasted for two years, this one might as well.” While an on-again, off-again eruption probably would not have much effect on air travel over the long term, it could affect the weather in Northern Europe, said Richard Wunderman, a vulcanologist with the Smithsonian Institution in Washington. The volcanic plume contains a lot of sulfur, he said, “that can become an aerosol up there that hangs around a long time reflecting sunlight.”

“It’s not enough that it’s probably going to be cooling the whole climate,” he added. But on a regional basis it could create what is called volcano weather, with smoglike conditions.

Unlike huge volcanic blasts like that at Mount Pinatubo in the Philippines in 1991, the eruption in southern Iceland began slowly about a month ago, with a series of fissures on the side of the volcano and what vulcanologists call fire fountaining, the spewing of hot magma through vents. Dr. Burton said that it was only when the magma found a new route through the volcano earlier this week — shifting to the summit, directly under the glacial ice — that the ash-rich eruption began.

That eruption late Wednesday created a plume of ash that spread out across Northern Europe at high altitudes, forcing aviation authorities to ground flights and close airports because of the risk of damage to aircraft, particularly the engines, from abrasive silicate particles.

Dr. Burton said that when the eruption shifted to the summit, there were indications that the silica content of the ash increased. “Theoretically, the more silica-rich the ash, the more risky or greater threat there is,” he said. But any volcanic plume is dangerous. “The plane is effectively sandblasted,” he said. “Even the windows can become frosted.”

Dr. Burton said the eruption was low on a measure of power called the volcanic explosivity index — certainly nowhere near Pinatubo, which rated a 6 on the 1 to 8 scale, or the 1980 explosive eruption of Mount St. Helens in Washington State, which rated a 5.

Pinatubo spewed so much ash, dust and aerosol particles into the atmosphere that it lowered average air temperatures worldwide for several years, as the particles blocked some sunlight from reaching the Earth. So far the Icelandic eruption has spewed far less material, and its location, in the high latitudes, also reduces its global impact. “The closer to the poles, the less effect it is likely to have,” Dr. Burton said.