Гримсвётн жанабаты: Исландия вулканы

Volcano in Iceland

Grímsvötn (; vötn = "waters", singular: vatn) is an active volcano with a (partially subglacial) fissure system located in Vatnajökull National Park, Iceland. The volcano itself is completely subglacial and located under the northwestern side of the Vatnajökull ice cap. The subglacial 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 Grímsvötn Laki volcanic system. Grímsvötn was erupting at the same time as Laki during 1783, but continued to erupt until 1785. Because most of the volcanic system lies underneath Vatnajökull, most of its eruptions have been subglacial and the interaction of magma and meltwater from the ice causes phreatomagmatic explosive activity. Within the Grímsvötn Laki volcanic system is a second central volcano called Thordarhyrna (Þórðarhyrna).

Eruptions in the caldera regularly cause glacial outbursts known as jökulhlaup. Eruptions or geothermal activity, melt enough ice to fill the Grímsvötn caldera with water, and the pressure may be enough to suddenly lift the ice cap, allowing huge quantities of water to escape rapidly. Earthquakes and seismic tremor may occur. Jökulhlaup can occur independent of eruptions or be followed by eruptions. 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.

A week long eruption occurred at Grímsvötn starting on 28 December 1998, but no glacial burst occurred. In November 2004, a week long eruption occurred. Volcanic ash from the eruption fell as far away as mainland Europe and caused short term disruption of airline traffic into Iceland, but again no glacial burst followed the eruption.

Harmonic tremors were recorded twice around Grímsvötn on 2 and 3 October 2010, possibly indicating an impending eruption. At the same time, sudden inflation was measured by GPS in the volcano, indicating magma movement under the caldera. On 1 November 2010 meltwater from the Vatnajökull glacier was flowing into the lake, suggesting that an eruption of the underlying volcano could be imminent. On 21 May 2011 at 19:25 UTC, an eruption began, with high plumes accompanied by multiple earthquakes, Until 25 May, the eruption scale had been larger than that of the 2010 eruption of Eyjafjallajökull. The ash cloud from the eruption rose to , and was so far 10 times larger than the 2004 eruption, and the strongest in Grímsvötn in the last 100 years. Disruption to air travel in Iceland commenced on 22 May, followed by Greenland, Scotland, Norway, Svalbard and a small part of Denmark on subsequent days. On 24 May the disruption spread to Northern Ireland and to airports in northern England. in the period 23–25 May was much less widespread than the 2010 disruption after the Eyjafjallajökull eruption. The eruption stopped at 02:40 UTC on 25 May 2011, although there was some explosive activity from the eruptive vents affecting only the area around the crater.

Tephra studies on soil samples from around the Vatnajökull ice cap, show that the Grímsvötn volcanic system has high activity for Iceland, and had between 4 to 14 explosive eruptions every 100 years (mean about 7 eruptions every 100 years) between 7600 years ago and 870 AD. For technical reasons only the last 10,200 years of explosive eruptions have been characterised locally, and the record gets more inaccurate with time especially prior to 1598, which is first eruption timed to the day. produced the Skaftáreldahraun lava flows, which cover a large part of south east Iceland.

There is the potential for mechanical interaction such as dyke propagation between Grímsvötn and Thordarhyrna. Interactions can also occur with the nearby Bárðarbunga volcano, which is part of a separate volcanic system. The compositional separation from nearby systems has been studied in some detail, and is used to assign lava and tephra deposits to the volcanic system. The volcanic system has crater rows extending to the south east; the long Laki–Grímsvötn fissure system and the long Rauðhólar Eldgígur fissure system.