The volcanic cloud of ash drifting in from Iceland has caused the longest closure of European airspace since World War II. Some scientists say the current event could be a warning sign of even bigger volcanic disruptions to come. As of Sunday afternoon, there was some indication that the eruptions from the Eyjafjallajokull volcano in Iceland may be abating. While cloud cover prevented scientists from getting a good view of the eruption, radar measurements suggested that the ash plume wasn't above 10,000 feet on Sunday, after rising to 30,000 earlier. "That's fairly good news," said Dave McGarvie, a volcanologist at the Open University in the U.K. "If [the eruption] stops for a day, it may be dying down."
Eyjafjallajokull has erupted three times in recent history: in 920, 1612 and 1821-1823. Because volcanic activity can occur in fits and starts, it is hard to make reliable predictions. Dr. McGarvie noted that when the volcano erupted in 1821, it stopped for months and then restarted. When a typical volcano erupts, it spews ash and a variety of gases into the air. However, when a volcano sitting under a thick ice sheet blows its top, as in Iceland, it can give rise to a larger and higher-rising ash plume. In such a case, the plume results from an explosive mix of molten rock, erupting magma and ice. When the magma hits the glacial ice, it cools extremely rapidly and in the process, shatters into fine, flour-like material, which is light enough to be carried miles into the sky.
At the same time, the emerging magma melts the ice. As more magma is ejected, it encounters larger amounts of meltwater, which generates more steam. These enormous steam plumes rise skyward, carrying with them volcanic gases and the magma-produced fine ash, which makes up the ash cloud floating above Europe. This interaction can last until all the ice near the volcanic vent has disappeared. Then the ash plume will only consist of the usual magma and volcanic gases emitted, the same as any typical volcano where ice isn't involved. Scientists at the U.K.'s National Environment Research Council recently got a close look at the ash cloud. Flying in a specially outfitted research aircraft, they tracked the edge of the plume on Britain's eastern coast, the North Sea and near the Dutch coastline.
Flying at just below 10,000 feet, the researchers aboard the Dornier 228 aircraft measured the height, density and position of the plume. They identified three distinct layers of volcanic residue. "Heavy, gritty particles seem to be sitting at around 8,000 feet, whilst lower down in the atmosphere there are sulfurous chemicals and finer dust particles," the research council said. The data are being analyzed and the results are expected to be used to help with forecasting models and by the aviation industry. Over the weekend, the U.K.'s Met Office said it had detected dust in the atmosphere and on the ground, a sign the material in the ash cloud is dispersing. "It's currently in the lower atmosphere but it will eventually fall to earth," said Dr. McGarvie. He says he was in Scotland on Saturday and saw the evidence first-hand. "My car was coated with fine ash," he noted.
Some researchers worry that the latest eruption could trigger similar explosions at a much-larger neighboring volcano, called Katla. The last three times that Eyjafjallajokull exploded, there has been an eruption at Katla within two or three years, and sometimes within a month or two. Katla is one of the most intensely watched volcanoes in Iceland, and its peak is just 15 miles from the peak of Eyjafjallajokull. Volcano experts say the magma chamber under Katla sits quite high above the earth's crust. Since Katla last erupted in 1918, enough time has gone by for a large amount of magma to collect. Magma doesn't only shoot up vertically from a volcano; it also moves laterally in the crust. The concern is that the recent eruption in Iceland may create subterranean magma flows that could disturb the magma chamber under Katla.
Since the ice over Katla is a much-thicker 2,300 feet, a big, sustained eruption there could potentially create an ash cloud that would easily dwarf the one hovering over Europe today. "We don't know the subterranean connection between the two volcanoes," says Dr. McGarvie. But the past eruption history "suggests a close link between the two." A handful of other scientists are studying a longer-term problem: the effect of climate change on volcanic eruptions. Some recent, early stage studies suggest that as the climate in Iceland warms and the ice cap melts, volcanic eruptions there could happen more frequently.
Imagine a floating cork, topped with a piece of lead; it will pop upward when the lead is taken off. Similarly, a shrinking ice cap will reduce the pressure on the earth's mantle, causing it to melt and creating magma. Mathematical models suggest that such processes may potentially lead to more volcanic eruptions in places like Iceland.
Author: Gautam Naik
