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    'Explosive' Katla Could Affect Global Temperature, Devastate Iceland

    By Story by AccuWeather.com's Jon Auciello
    April 28, 2010, 5:33:34 AM EDT

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    The recent volcanic activity of Iceland's Eyjafjallajokull has shed a spotlight upon the consequences of large-scale volcanic eruptions.

    Katla is a much larger Icelandic volcano system located approximately 17 miles (27 km) to the east Eyjafjallajokull. Geoscientists are wary not only for the damage an eruption could cause Iceland, but also the international implications that could follow, including global temperature change.

    "There's been a concern because the last two eruptions of Eyjafjallajokull have corresponded with eruptions from Katla," explained Peter La Femina, Assistant Professor of Geoscience at the Pennsylvania State University.

    Volcanic activity has occurred twice thus far in 2010 at Eyjafjallajokull, on March 20 and April 14. The second eruption created the giant ash cloud over Europe.

    Additional eruptions there have also been documented in the years 920 and 1612, and from 1821 to 1823. Katla has followed suit with its own eruptions after each of those periods.

    "Katla is due to erupt," said Barry Voight, Professor of Geology and Geological Engineering at the Pennsylvania State University. "It's quite unusual for it not to erupt, considering it had erupted every 40 years since its last major eruption in 1918."

    While more recent activity of Katla has occurred in 1955 and 1999, neither instance was strong enough to break the layer of ice covering the volcano.

    Much like Eyjafjallajokull, Katla is covered by a glacier called Myrdalsjokull. This ice cap is 230 square miles (595 square km), nearly six times the size of Eyjafjallajokull.

    The far-larger glacier situated on top of the volcano has potential to devastate the local community's highways, bridges and farmland with flooding as the magma pushes through to the surface and melts the glacial ice above it. This glacier outburst flooding, or jokulhlaup, is notorious throughout Iceland's history for causing destruction.

    According to La Femina, Katla's last major eruption in 1918 was "very, very explosive."

    In addition to creating havoc upon the local community in Iceland, the ramifications of this volcano could again extend far beyond the island nation.

    In June 1991, the massive eruption of Mount Pinatubo in the Philippines rocked the Pacific region and led to a global drop in temperature.

    "That volcano produced enough ash and aerosols that were injected into the atmosphere that cooled the globe for up to, I think, 2 degrees centigrade for several years," said La Femina.


    That eruption was categorized as a 6 on the Volcanic Explosivity Index (VEI). Eruptions on the VEI range from 0 to 8, with the 1980 Mount St. Helens event measured as a VEI 5.

    La Femina said that Katla historically erupts in the VEI 3 to 4 range. Eyjafjallajokull's most recent eruption was a VEI 2.

    However, the magmas of both Mount Pinatubo and Katla are similar, which raises the concern of this volcano becoming active again.

    "Eyjafjallajokull is what we call a basaltic or a basaltic-andesitic volcano," explained La Femina. "So it has magmas that are low in silica concentration. This usually leads to very effusive eruptions."

    Meanwhile, Katla has the whole range of magmatic compositions from basalt to rhyolite, which are richer in silica.

    "So it has the ability to be much, much more explosive," he said.

    However, the effect of these gases in the years following their release into the atmosphere are much more complex than just straight cooling.

    "Not only did we have global cooling, but there was actually some warming during the Northern Hemisphere winters," said La Femina.

    While a historical connection between eruptions at Eyjafjallajokull triggering activity in Katla can be made, La Femina is not convinced the two are directly related. He said their relationship is not fully understood, citing the difference in magma composition at each volcano.

    "The trigger could be from below having magma intrude from one system to the other. It could be stress-triggering the eruption and migration of magma at Eyjafjallajokull or could trigger migration at Katla."


    So when will the current activity at Eyjafjallajokull end?

    "During the last eruption of Eyjafjallajokull in 1821, the eruption actually lasted from 1821 to 1823," La Femina said.

    "It could go on for a year, it could stop tomorrow. We just don't know."

    On April 20, La Femina told AccuWeather.com his colleagues at the Icelandic Meteorological Office had yet to see signs of any unusual seismic activity from Katla.

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