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Grímsvötn ((:ˈkrimsvœʰtn̥);〔(【引用サイトリンク】title=How to pronounce /grímsvötn/ )〕 ''vötn'' = "waters", singular: ) is a volcano in South-East Iceland. It is in the highlands of Iceland at the northwestern side of the Vatnajökull ice-cap. The caldera is at , at an elevation of . Beneath the caldera is the magma chamber of the Grímsvötn volcano. Grímsvötn is a basaltic volcano which has the highest eruption frequency of all the volcanoes in Iceland and has a southwest-northeast-trending fissure system. The massive climate-impacting Laki fissure eruption of 1783–1784 was a part of the same fissure system. Grímsvötn was erupting at the same time as Laki during 1783, but continued to erupt until 1785. Because most of the volcano lies underneath Vatnajökull, most of its eruptions have been subglacial and the interaction of magma and meltwater from the ice causes phreatomagmatic explosive activity. On 21 May 2011 at 19:25 UTC, an eruption began, with high plumes accompanied by multiple earthquakes,〔(Eldgos í Grímsvötnum ), 24 May 2011 (in Islandic)〕 resulting in cancellation of 900 flights in Iceland,〔〔(Iceland Volcano and Earthquake blog )〕 and in the United Kingdom, Greenland, Germany, Ireland and Norway on 22–25 May. Until 25 May the eruption scale had been larger than that of the 2010 eruption of Eyjafjallajökull. The eruption stopped at 02:40 UTC on 25 May 2011, although there was some explosive activity from the tephra vents affecting only the area around the crater.〔(【引用サイトリンク】url=http://www.metoffice.gov.uk/aviation/vaac/data/VAG_1306323708.png )〕〔(【引用サイトリンク】url=http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2180 )〕 ==Jökulhlaup== Eruptions in the caldera regularly cause glacial outbursts known as jökulhlaup.〔() Jökulhlaup figure 8.1〕 Eruptions melt enough ice to fill the Grímsvötn caldera with water, and the pressure may be enough to suddenly lift the icecap, allowing huge quantities of water to escape rapidly. Consequently, the Grímsvötn caldera is monitored very carefully. When a large eruption occurred in 1996, geologists knew well in advance that a glacial burst was imminent. It did not occur until several weeks after the eruption finished, but monitoring ensured that the Icelandic ring road (Hringvegur) was closed when the burst occurred. A section of road across the Skeiðará sandur was washed away in the ensuing flood, but no one was hurt. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grímsvötn」の詳細全文を読む スポンサード リンク
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