Grímsvötn (Icelandic pronunciation: [ˈkrimsˌvœhtn̥] ; vötn = "waters", singular: vatn) is an active volcano with a (partially subglacial) fissure system located in Vatnajökull National Park, Iceland. The central volcano is completely subglacial and located under the northwestern side of the Vatnajökull ice cap. The subglacial caldera is at 64°25′N 17°20′W, at an elevation of 1,725 m (5,659 ft). 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. It has a southwest-northeast-trending fissure system. The massive climate-impacting Laki fissure eruption of 1783–1784 took place in 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).
Jökulhlaup 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. Jökulhlaup independent of eruptions occurred in November, December 2021 and October 2022. Jökulhlaup which were followed by eruptions occurred in 1922, 1934 and 2004. 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.
Eruption history between 1990 and today
Gjálp 1996 (See also the main article: 1996 eruption of Gjálp The Gjálp fissure vent eruption in 1996 revealed that an interaction may exist between Bárðarbunga and Grímsvötn. A strong earthquake at Bárðarbunga, about magnitude 5, is believed to have been related to the triggering of the eruption in Gjálp. On the other hand, because the magma erupted showed strong connections to the Grímsvötn Volcanic System according to petrology studies, the 1996 as well as a former eruption at Gjálp in the 1930s are thought to have taken place within Grímsvötn Volcanic system.
1998 and 2004 eruptions
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.
2011 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 a lake, suggesting that an eruption of the underlying volcano could be imminent.
On 21 May 2011 at 19:25 UTC, an eruption began, with 12 km (7 mi) 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 20 km (12 mi), 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. The cancellation of 900 out of 90,000 European flights 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.
2020 onward threats of eruption In June 2020, the Icelandic Meteorological Office (IMO) issued a warning that an eruption might take place in the coming weeks or months, following scientists reporting high levels of sulfur dioxide, which is indicative of the presence of shallow magma. IMO warned that a glacial flood as a result of melting ice could trigger an eruption. No eruption occurred. In September 2021, an increase in water outflow from under the Vatnajökull ice cap was reported. The water contains elevated levels of dissolved hydrogen sulfide, suggesting increased volcanic activity under the ice. Jökulhlaup (glacial lake flooding) can occur before or after an eruption. On 4 December 2021, a jökulhlaup occurred from Grímsvötn into the Gígjukvísl river, with an average flow of 2,600 m3/s (92,000 cu ft/s). Two days later, the Icelandic Meteorological Office increased the alert level for Grímsvötn from yellow to orange, after a series of earthquakes was detected. On 7 December, the alert level was lowered back to yellow, after seismic activity decreased and no signs of eruptive activity were detected. On 11 December 2023, a jökulhlaup followed in time, a Mw 4.5 earthquake.
… excerpt ends here. Continue reading the full article.
