Geology And Geophysics

What Happened the last Time the Eyjafjallajokull Volcano Erupted

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Because of its position over the Mid-Atlantic Ridge and between two fault plates, Iceland is a land of volcanoes. In fact, it has 130 volcanic mountains, and 18 of these have erupted since settlement began on the island in 874 AD. Over 1/3 of the world’s total lava output comes from Iceland. For 700 years, from 920, until 1612, Eyjafjallajokull, or “island-mountain glacier”, Iceland’s temperamental volcano, remained silent. We know it erupted in 1612, and then, again a little over 200 years later, in 1821.

, is one of Iceland’s relatively small ice caps, to the north of Skogar and west of Myrdalsjokull. The ice cap covers the volcano caldera at an elevation of 5, 466 ft., and the crater measures about 1.9-2.5 miles in diameter. In 1821, when the volcano erupted, it was considered a minor eruption. The real hazard during this episode was that the ash that resulted contained a high level of fluoride, which is harmful to humans and all other mammals. This eruption began on December 19th and 20th, with some explosive eruptions and lasted for several days, leaving a heavy ash layer to the south and west. During the period from August to December 1822, the volcano became less active, but it was noted that there were instances of deaths of cattle and sheep, that the farmers in Iceland attributed to the poisoning effects of the fluoride. Ash from these eruptions is found over southern Iceland, dark grey, and containing small and intermediate rock.

The most dangerous and frightening result of the current eruption is the fact that this could very well trigger an eruption from Eyjafjallajokull’s neighbor, Katla. This happened in 1821, and Katla is much larger and much more dangerous. Scientists are well aware of the fact that one volcano triggers another in an environment that is composed chiefly of volcanoes. And, where this first recent series of volcanic activity this year, in 2010, has caused inconvenience with its ash cloud over Europe, the fear is that if it causes Katla to erupt as in 1821, the effects will cause a world wide cool down in temperatures.

In 1783, a few decades before the 1821 eruptions, another Icelandic volcano, Laki, erupted. This event actually changed weather conditions world wide. It caused massive snow falls on the American east coast and brought excessive drought to the Middle East. It was also responsible for the deaths of over 1/3 of Iceland’s population.

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