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    Saturday, January 19, 2008


    Icelanders Battle Volcano - Save Port

    The people of Iceland must repeatedly battle one of the most violent forces of nature - volcanic eruptions. The same forces that created Iceland threaten to destroy Man's intrusions.


    Formation of Iceland

    Iceland plume

    The Iceland Plume is an upwelling of anomalously hot rock in the Earth's mantle beneath Iceland whose origin probably lies at the boundary between the core and the mantle at ca. 2880 km depth. It is generally thought to be the cause of the formation of Iceland and its volcanism, which characterizes the island to the present day, according to the plume theory of W. Jason Morgan.

    Geological history

    The plume, which bears the name of Iceland and lies roughly beneath the center of the island, is considerably older than Iceland. Volcanic rocks related to it are found to both sides of the coast of southern Greenland and had their ages determined to lie between 58 and 64 million years; this coincides with the opening of the north Atlantic in the late Paleocene and early Eocene. It is generally thought that the volcanism was caused by the flow of hot material from the plume head into regions beneath the lithosphere which had previously been thinned by rifting and produced large amounts of melt there. The exact position of the plume at that time is controversial, but was probably beneath central Greenland; it is also not entirely clear whether the plume had ascended from the deep mantle only at that time or whether it is much older and also responsible for the old volcanism in northern Greenland, the Ellesmere Island Volcanics on Ellesmere Island, and in the Arctic Ocean (Alpha Ridge). All of these volcanics are part of the High Arctic Large Igneous Province. (see url for remainder of article)


    Excerpt: (for complete article, access url)

    Geological activity

    A geologically old land, Iceland is located on both a geological hot spot, thought to be caused by a mantle plume, and the Mid-Atlantic Ridge, which runs right through it. This combined location means that geologically the island is extremely active, having many volcanoes, notably Hekla, Eldgjá, and Eldfell. The volcanic eruption of Laki in 1783–1784 caused a famine that killed nearly a quarter of the island's population;[7] the eruption caused dust clouds and haze to appear over most of Europe and parts of Asia and Africa for several months after the eruption.

    There are also many geysers in Iceland, including Geysir, from which the English name is derived. With this widespread availability of geothermal power, and also because of the numerous rivers and waterfalls that are harnessed for hydroelectricity, most residents have hot water and home heat for a low price. The island itself is composed primarily of basalt, a low-silica lava associated with effusive volcanism like Hawaii. There is, however, a variety of different kinds of volcanoes in Iceland, many of which produce more evolved lavas such as rhyolite and andesite.

    Dettifoss, the most powerful waterfall in Europe, is located in north-eastern Iceland.
    Dettifoss, the most powerful waterfall in Europe, is located in north-eastern Iceland.

    Iceland controls Surtsey, two of the youngest islands in the world. It rose above the ocean in a series of volcanic eruptions between November 8, 1963 and June 5, 1968.[6]


    Because of its volcanic activity, Iceland's inhabitants must deal with eruptions quite often. To save their port, vital to the existence of the town, the residents of a threarened town fight back - and win.

    Eldfell, Heimaey, Iceland Location: 63.4N, 20.3W
    Elevation: 915 feet (279 m)
    Last Updated: 10 April 2001


    The 1973 eruption on the island of Heimaey is a classic example of the struggle between man and volcanoes. With a heroic effort the people of Iceland saved the town of Vestmannaeyjar and the country's most important fishing port.

    Except where noted, all photographs are by the late Svienn Eirikksen, fire marshal of the town of Vestmannaeyjar. Photographs courtesy of the U.S. Geological Survey.

    The island of Heimaey with the growth of the island in 1973, the location of the eruptive fissure, and the location of Eldfell, the 1973 cone. Modified from Williams and Moore, 1983.

    View of Heimaey before the eruption. The town of Vestmannaeyjar and the harbor are in the foreground. Helgafell, a prehistoric cone, is in the background on the right. From Williams and Moore, 1983.

    Eldfell ("fire mountain" in Icelandic) is a volcano on the island of Heimaey in the Vestmannaeyjar archipelago 15 miles (25 km) south of Iceland. In January of 1973, an eruption began along a 1.5 mile (2 km) long fissure not far from the center of the town of Vestmannaeyjar. The fissure extended across the entire island, producing a spectacular curtain of fire. Nearly all of the island's 5,300 residents were evacuated to the mainland.

    Within two days, activity became localized to a central vent and fire fountains constructed a cinder and spatter cone 350 feet (100 m) above sea level.

    Strong winds blew tephra from the eruption and buried homes in the town Vestmannaeyjar.

    Massive block lava flows threatened the town and the fishing port.

    A submarine eruption cut the cable that supplied power from the mainland. The initial eruption rate was close to 130 cubic yards (100 cubic meters) per second. By the middle of April, the eruption rate had dropped to 7 cubic yards (5 cubic meters) per second. The eruption stopped in early July.

    About 70 homes and farms were buried under tephra and 300 buildings were burned by fires or buried under lava flows.

    This eruption is famous because the Icelanders sprayed sea water on the lava to slow and stop its movement. It was the largest effort ever exerted to control volcanic activity. More than 19 miles (30 km) of pipe and 43 pumps were used to deliver sea water at rate up to 1.3 cubic yards (1 cubic meters) per second. By the end of the eruption 8 million cubic yards (6 million cubic meters) of water had been pumped onto the flows.

    View in July 1974 of the same scene as above after removal of the lava. The building were restored. From Williams and Moore, 1983.

    The town of Vestmannaeyjar and the harbor after the eruption. Eldfell and the 1973 lava flows are just beyond the town. Photograph by Robin Holcomb, U.S. Geological Survey.

    Not only did the tremendous efforts save the port they actually improved it. The residents returned to rebuild their town and even used the heat from the cooling lava to construct a district heating system. This vertical aerial photograph of the island shows the improved harbor, Helgafell and Eldfell cones, and the new land added to the island. Photograph by Iceland Geodetic Survey, September, 8, 1973. From Williams and Moore, 1983.


    Photos of Iceland:

    Image:Iceland Dettifoss 1972-4.jpg

    Dettifoss Falls

    Dettifoss: most powerful waterfall in Europe


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