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Iceland hotspot

2007 Schools Wikipedia Selection. Related subjects: Geology and geophysics

   Eruption at Krafla, 1984
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   Eruption at Krafla, 1984

   The Iceland hotspot is a hotspot which is partly responsible for the
   high volcanic activity which has formed the island of Iceland.

Evidence

   Iceland is one of the most active volcanic regions in the world, with
   eruptions occurring on average roughly every five years. About a third
   of the basaltic lavas erupted in recorded history have been produced by
   Icelandic eruptions. Notable eruptions have included that of Eldgjá in
   984 (the world's largest basaltic eruption ever witnessed), Laki in
   1783 (the world's second largest), and several eruptions beneath ice
   caps, which have generated devastating glacial bursts, most recently in
   1996.

   Iceland's location astride the Mid-Atlantic Ridge, where the Eurasian
   and North American Plates are moving apart, is partly responsible for
   this intense volcanic activity, but an additional cause is necessary to
   explain why Iceland is a substantial island while the rest of the ridge
   mostly consists of seamounts, with peaks below sea level. It is
   believed that a mantle plume must lie beneath the island, enhancing the
   volcanism already caused by plate separation.

   As well as driving volcanism in the centre of the island, the plume is
   also believed to feed magma to the Reykjanes ridge, another region of
   enhanced volcanism to the southwest of Iceland's main volcanic zone.

Nature of the hotspot

   The plume, of which the Iceland hotspot is thought to be the surface
   expression, is believed to be quite narrow, perhaps 100 km across, and
   extends down to at least 400–650 km beneath the Earth's surface, and
   possibly down to the core-mantle boundary. As well as being a region of
   higher temperature than the surrounding mantle, it is also believed to
   have a higher concentration of water. The presence of water in magma
   reduces the melting temperature, and so the wetness of the Iceland
   plume probably also plays a role in enhancing Icelandic volcanism.

   Some geologists have questioned whether the Iceland hotspot has the
   same origin as other hotspots such as the Hawaii hotspot. While the
   Hawaiian island chain and the Emperor Seamounts show a clear
   time-progressive volcanic track caused by the movement of the Pacific
   Plate over the Hawaiian hotspot, no such track can be seen at Iceland,
   possibly because the plume which is assumed to cause it may have been
   located beneath the thick Greenland craton for a significant time.

   Studies suggest that the hotspot is only 50-100 K hotter than its
   surroundings, which may not be a great enough difference to drive a
   buoyant plume. There is an ongoing discussion whether the hotspot is
   caused by a deep mantle plume or originates at a much shallower depth.

   Retrieved from " http://en.wikipedia.org/wiki/Iceland_hotspot"
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   with only minor checks and changes (see www.wikipedia.org for details
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