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Iceland's eruptions could have global consequences

Blasts of lava and ash erupted from a volcano in southern Iceland on Monday and small tremors rocked the ground. This created fears of a larger explosion at the nearby Katla volcano.

History has shown that when the Eyjafjallajökull volcano erupts, Katla follows — the only question is how soon. And Katla, located under the massive Myrdalsjökull ice cap^(d), threatens disastrous floods and explosive blasts when it^(d) blows.

Saturday's eruption at Eyjafjallajökull (pronounced AYA-feeyapla-yurkul) — dormant for nearly 200 years — forced at least 500 people to evacuate. Most have returned to their homes, but authorities were waiting for scientific assessments to determine whether they were safe to stay. Residents of 14 farms nearest to the eruption site were told to stay away.

Several small tremors were felt early Monday, followed by lava and steam rocketing into the air.

Iceland sits on a large volcanic hot spot just between the Eurasian plate and the North American plate. Eruptions, common throughout Iceland's history, are often caused by seismic activity when the Earth's plates move and when magma^(a) from deep underground pushes its^(a) way to the surface.

Like earthquakes, predicting the timing of volcanic eruptions is an imprecise science. An eruption at the Katla volcano could be disastrous, however — both for Iceland and other nations.

Iceland's Laki volcano erupted in 1783, freeing gases that turned into smog. The smog made dramatic changes to the weather. Many died from gas poisoning in the British Isles. Crop production fell in Western Europe, and this caused famine. This is why some even linked the eruption to the French Revolution. Painters^(b) in the 18th century illustrated bright red sunsets in their^(b) works.

The winter of 1784 was also one of the longest and coldest on record in North America. New England reported a record stretch of below-zero temperatures and New Jersey reported record amounts of snow. The Mississippi River also reportedly froze in New Orleans.

Unlike the powerful volcanoes along the Pacific Ocean, Iceland's volcanoes^(c) occur in an area where two of the earth's plates are moving apart from each other. They^(c) are also unique in that many erupt under ice sheets with little warning. It is one of the few places in the world where volcanic eruptions often go undetected because they can't be easily seen.

Magnus Tumi Gudmundsson, a geologist at the University of Iceland who flew over the site on Monday, said the beginning of Saturday's eruption was so indistinct that it initially went undetected by geological instruments. Many of the tremors were below magnitude 2.6.

Using thermal cameras and radar to map the lava flow, Gudmundsson and other scientists were able to determine that the lava from Eyjafjallajökull was not moving toward the ice caps, reducing any threat of floods. He said he and other scientists were watching Katla but Monday's trip was meant to assess immediate risk.

Andy Russell from Newcastle University went with a team to Iceland before the eruption. "From records, we know that every time Eyjafjallajökull erupts, Katla has also erupted". Russell said past Katla eruptions have caused floods the size of the Amazon and sent rocks as big as houses tumbling down valleys and roads. The last major eruption took place in 1918. Floods followed in as little as an hour.

Those eruptions have posed risks to residents nearby, but most of Iceland's current population of 320,000 live in the capital of Reykjavik on the western part of the island.

Southern Iceland is not very populated but has both glaciers and unstable volcanoes — a destructive combination. (…)

Adapted from: http://usatoday30.usatoday.com/tech/science/2010-03-22-iceland-volcano_N.htm.