‘Glacial Ice Produced Ash in Volcanic Eruption’

The Eyjafjallajokull volcano of Iceland, whose eruption caused all planes in Europe to be grounded, means a “glacier separated from an island” in Icelandic. The eruption occurred beneath a glacier. Volcano experts said, however, that without the glacier, the eruption would not have caused such huge damage, adding, the glacier made the volcano “furious.”

Magma from the volcano consists of low-viscosity basalt. If magma’s viscosity is low, it flows out from a volcano like water instead of spouting out. Since the explosive power is low, the eruption releases less volcanic ash in this case. Yoon Seong-hyo, a professor of earth science education at Pusan National University, said, “If basaltic magma meets glacial ice, however, the explosive power grows and a large volume of volcanic ash is created.”

Water is one factor affecting explosive power. If water is mixed with magma, the former evaporates due to high temperature. Vapor in magma drastically expands when exposed to air due to low pressure. Therefore, magma containing water pops out of a volcano simultaneously in an eruption.

Magma from the Eyjafjallajokull volcano contained a large amount of water since a glacier is beneath the volcano. Yoon said, “As soon as water met hot magma of more than 1,200 degrees Celsius, it turned into vapor,” adding, “This led to strong explosive power, sending volcanic ash into the sky more than 10 kilometers high.”

The glacier also contributed to generating a huge amount of volcanic ash enough to cover the whole sky in Europe. Basaltic magma flows down long distances and turns into black stones with small holes, which are commonly seen on Jeju lsland. When such magma meets glacial ice, however, it rapidly cools and hardens before its particles stick together. This generates massive volcanic ash less than two millimeters in diameter. Yoon said, “It’s like a huge rock able to cover a large swath of land being reduced to powder and going up to the sky.”

The volcano stopped spouting out ash Tuesday and began gushing out liquid-like basaltic magma. Hwang Jae-ha, chief researcher at the geological survey department of the Korea Institute of Geoscience and Mineral Resources, said, “This is because no water exists since the glacier near the crater turned into vapor.”

If volcanic activities begin in areas covered with glaciers near the volcano, ash will go up in the sky again. “Iceland is on an oceanic ridge where the earth’s crust cracks, so volcanic activities occur frequently,” Hwang said. “Affected by the eruption last week, the same volcano or others can erupt.”

The Korea Meteorological Administration said Monday, “Ash from the Eyjafjallajokull volcano is expected to pass the skies of Korea between Friday and next Monday,” adding, “The ash is spreading to all of Europe but no big impact on Korea is expected with air currents moving at a slow pace.”

jermes@donga.com