A subglacial volcano is a volcanic form produced by
subglacial eruptions or eruptions beneath the surface of a glacieror ice sheetwhich is then melted into a lakeby the rising lava. Today they are most common in Icelandand Antarctica; olde r formations of this type are found also in British Columbiaand Yukon Territory, Canada.
During the eruption, the heat of the lava from the subglacial volcano melts the overlying ice. The water quickly cools the lava, resulting in
pillow lavashapes similar to those of underwater volcanoes. When the pillow lavas break off and roll down the volcano slopes, pillow breccia, tuffbreccia, and hyaloclastiteform. The melted water may be released from below the ice as happened in Icelandin 1996 when the Grimsvötn caldera erupted, melted 3 cubic km ice and gave rise to a large glacial lake outburst flood.
The shape of subglacial volcanoes tends to be quite characteristic and unusual, with a flattened top and steep sides supported against collapse by the pressure of the surrounding ice and meltwater. If the volcano eventually melts completely through the ice layer, then horizontal lava flows are deposited, and the top of the volcano assumes a nearly-level form. However, if significant amounts of lava are later erupted
subaerially, then the volcano may assume a more conventional shape. The more distinctly flat-topped, steep-sided subglacial volcanoes are called tuyas, named after Tuya Buttein northern British Columbia by Canadian geologist Bill Mathewsin 1947. In Iceland, such volcanoes are also known as table mountains.
On January, 2008, the
British Antarctic Survey(Bas) scientists led by Hugh Corr and David Vaughan, reported (in the journal Nature Geoscience) that 2,200 years ago, a volcanoerupted under Antarcticaice sheet (based on airbornesurvey with radar images). The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier. [ [http://news.bbc.co.uk/2/hi/science/nature/7194579.stm BBC NEWS, Ancient Antarctic eruption noted] ]
* [http://gsc.nrcan.gc.ca/volcanoes/type_e.php Volcanoes of Canada: Types of volcanoes] Accessed Jan. 8, 2006
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