Grímsvötn

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  • Country
  • Subregion Name
  • Primary Volcano Type
  • Last Known Eruption
  • 64.42°N
  • 17.33°W

  • 1725 m
    5658 ft

  • 373010
  • Latitude
  • Longitude

  • Summit
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26 March-1 April 2014

According to the Icelandic Meteorological Office, a small glacial outburst flood (jokulhlaup) from Grímsvötn's subglacial lake was occurring on 27 March, increasing the water level in the Gígjukvísl River; it was expected to peak by the end of the week and remain small. Electrical conductivity measurements indicated a considerable increase of a geothermal contribution to the river water. Seismic tremor had increased due to the flood and not volcanic activity. The report warned that hydrogen sulfide released from the floodwater as it drains is particularly potent at the river outlet at the ice margin, where concentrations may reach poisonous levels.

Source: Icelandic Met Office



 Available Weekly Reports


2014: January | March
2011: May
2004: October


26 March-1 April 2014

According to the Icelandic Meteorological Office, a small glacial outburst flood (jokulhlaup) from Grímsvötn's subglacial lake was occurring on 27 March, increasing the water level in the Gígjukvísl River; it was expected to peak by the end of the week and remain small. Electrical conductivity measurements indicated a considerable increase of a geothermal contribution to the river water. Seismic tremor had increased due to the flood and not volcanic activity. The report warned that hydrogen sulfide released from the floodwater as it drains is particularly potent at the river outlet at the ice margin, where concentrations may reach poisonous levels.

Source: Icelandic Met Office


15 January-21 January 2014

According to the Icelandic Meteorological Office, the level of the Skaftá river at Sveinstindur and electrical conductivity both rose during 18-19 January indicating a glacial outburst flood (jokulhlaup), originating from Grímsvötn's western Skaftá ice cauldron. The jokulhlaup was unconfirmed without visual observations, however. Flood waters peaked on 20 January and then began to subside on 21 January. The report noted that floods in Skaftá source from two ice cauldrons formed by persistent geothermal activity beneath Vatnajökull. The cauldrons drain an average every two years, producing floods of up to 1,500 cubic meters per second.

Source: Icelandic Met Office


25 May-31 May 2011

According to scientists from the Institute of Earth Sciences at the University of Iceland and the Icelandic Meteorological Office, explosive activity occurred from four tephra cones surrounded by water in Grímsvötn's crater during the evening of 24 May. Pulsating ash plumes rose a few kilometers above the cones, producing only local fallout of material. Seismic tremor decreased. On 25 May, observers noted steam bursts from the crater. Tephra fallout was noted only in the vicinity of the eruption site. Pilots reported widespread ash in layers 5-7 km W of the volcano and also some ash haze below 3 km (9,800 ft) a.s.l. to the SW. Seismic tremor decreased considerably. On 26 May minor steam explosions continued from the crater. According to news articles, air traffic disruption was reduced to parts of Norway and Sweden. On 28 May tremor rapidly decreased then disappeared, and on 30 May participants on the Iceland Glaciological Society's spring expedition confirmed that the eruption had ended. Satellite imagery and visual observations showed that only small amounts of ice melted during the eruption; no signs of flooding had been detected.

Sources: Institute of Earth Sciences, Icelandic Met Office, Agence France-Presse (AFP)


18 May-24 May 2011

According to scientists from the Institute of Earth Sciences at the University of Iceland and the Icelandic Meteorological Office, an eruption from the subglacial Grímsvötn volcano began on 21 May following about an hour of tremor. A GPS-station on the rim of the Grímsvötn caldera had revealed continuous inflation and expansion of few centimeters per year since the 2004 eruption, interpreted as inflow of magma to a shallow chamber. Other precursors over the previous few months were increased seismicity, including some bursts of tremor, and increased geothermal activity.

The eruption began at 1630 on 21 May, and at 2000 the eruption plume rose to an altitude over 20 km (65,000 ft) a.s.l. The plume altitude fell to 15 km (49,200 ft) a.s.l. during the night but occasionally still rose to 20 km (65,000 ft) a.s.l. Ash from the lower part of the eruption plume drifted S and at higher altitudes drifted E. A few hours after the onset of the eruption ashfall began over areas S of the Vatnajökull ice cap, more than 50 km from the eruption site. Earthquake locations and limited observations during an initial overflight suggested that the eruption site was in the SW part of the caldera, where the 2004 eruption was located. According to news articles, the road in Skeidarársandur, S of Vatnajökull and part of the ring road around Iceland, closed and remained closed through 24 May.

During the morning of 22 May the plume rose to an altitude of 10-15 km (32,800-49,200 ft) a.s.l. The color of the plume was brown-to-grayish and sometimes black close to the source. Most of the plume drifted S, but lower parts traveled SW. Tephra fall was concentrated to the S and to a lesser extent N and E. In the afternoon lightning strikes ranged from 60-70 per hour (up to 300 during one hour) and were most frequent in the ash plume to the S. News outlets noted that the Keflavík airport closed. Ashfall was reported from the Reykjavík area in the SW to Tröllaskagi Peninsula in the N. An article also stated that, according to a geophysicist, the eruption was the largest for Grímsvötn in 100 years, was similar to the eruption of 1873, and was larger than the Eyjafjallajökull eruption of 2010.

During 22-23 May the ash plume rose to altitudes of 5-10 km (16,400-32,800 ft) a.s.l. and drifted S at lower altitudes and W at altitudes 8 km (26,200 ft) a.s.l. and higher. Ashfall was detected in several areas throughout Iceland except in some areas to the NW. On 24 May the ash plume was estimated to be mostly below 5 km (16,400 ft) a.s.l. because meteorological clouds over the glacier were at 5-7 km (16,400-23,000 ft) a.s.l. and the plume only briefly rose above the cloud deck. Satellite images showed the plume extending over 800 km from the eruption site towards the S and SE. News articles reported that dozens of carriers rerouted or cancelled flights in Norway, Denmark, and Scotland.

Sources: Institute of Earth Sciences, Icelandic Met Office, Iceland Review, Associated Press, The Local (Sweden)


27 October-2 November 2004

According to scientists from the Institute of Earth Sciences at the University of Iceland and the Icelandic Meteorological Office, an eruption began at the subglacial Grímsvötn volcano on 1 November around 2100. The eruption was preceded by both long-term and short-term precursors, and was triggered by the release of overburden pressure associated with a glacial outburst flood (jokulhlaup), originating from the Grímsvötn subglacial caldera lake.

Seismicity originally increased at the volcano in mid-2003, about the same time uplift exceeded a maximum reached in 1998: the last eruption at Grímsvötn occurred within the volcano's caldera beginning on 18 December 1998 and resulted in a catastrophic flood. Additional uplift and expansion of the volcano since mid-2003 suggested the approaching failure of the volcano. Seismicity further increased in late October 2004, and on 26 October high-frequency tremor indicated increased water flow from the caldera lake and suggested that a glacial outburst flood was about to begin. On 29 October, the amount of discharge increased in the Skeidara River. About 3 hours before the eruption began an intense swarm of volcanic earthquakes started, changing to continuous low-frequency tremor at the onset of the eruption. The release in overburden pressure associated with the outburst flood triggered the eruption. The amount of drop in water level in the Grímsvötn caldera at the onset of the eruption is uncertain, but was probably on the order of 10-20 m, corresponding to a pressure change of 0.1-0.2 MPa at the volcano's surface. This modest pressure change triggered the eruption because internal pressure in the Grímsvötn shallow magma chamber was high after continuous inflow of magma to the volcano since 1998.

The London VAAC reported that the ash plume produced from the eruption reached a height of ~12.2 km a.s.l. According to news articles, the eruption occurred in an unpopulated region so no evacuations were needed, but air traffic was diverted away from the region.

Observations on 2 November revealed that the eruption was occurring from a circular vent ~1 km in diameter in the SE part of the volcano's crater. The ice thickness in this part of the Grímsvötn caldera was ~200 m prior to the eruption. On 3 November, eruptive activity occurred in pulses, resulting in a changing eruption column height from 8-9 km to 13-14 km above the volcano. The ash fall sector extended at least 150 km from the eruption site. The distal ash plume was observed in Norway, Finland, and Sweden.

Sources: Institute of Earth Sciences, London Volcanic Ash Advisory Centre (VAAC), Associated Press, Reuters


Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2011 May 21 2011 May 28 Confirmed 4 Historical Observations SW part of the caldera
2004 Nov 1 2004 Nov 4 Confirmed 3 Historical Observations SW and east sides of caldera
1998 Dec 18 1998 Dec 28 Confirmed 3 Historical Observations South caldera wall
1996 Sep 30 1996 Nov 6 Confirmed 3 Historical Observations Gjálp (fissure N of caldera rim)
[ 1984 Aug 20 (in or before) ] [ Unknown ] Uncertain 0  
1983 May 28 1983 Jun 2 Confirmed 2 Historical Observations Near south caldera wall
[ 1972 Mar ] [ 1972 Apr ] Uncertain 0  
[ 1954 Jul ] [ Unknown ] Uncertain 1   North and south part of caldera
1954 Jan 15 ± 45 days Unknown Confirmed 1 Historical Observations
[ 1948 Feb ] [ Unknown ] Uncertain 0  
[ 1945 Sep 25 (?) ] [ Unknown ] Uncertain 1  
[ 1941 Apr ] [ 1941 Aug ] Uncertain 0  
[ 1939 Jun ] [ Unknown ] Uncertain 0  
1938 May Unknown Confirmed 1 Historical Observations 8 km N of Svartibunki
1934 Dec 21 1934 Dec 26 Confirmed   Unknown Vatnajökull
1934 Mar 30 1934 Apr 7 Confirmed 2 Historical Observations Near south caldera wall
1933 Nov 29 ± 1 days 1933 Dec 9 ± 1 days Confirmed 1 Historical Observations North of Grímsvötn caldera
1922 Sep 29 1922 Oct 23 Confirmed 2 Historical Observations
1919 Unknown Confirmed 2 Unknown
1910 Unknown Confirmed   Historical Observations
1902 Dec 1904 Jan 12 Confirmed 4 Historical Observations Grímsvötn and Thordarhyrna
1897 Unknown Confirmed 2 Unknown
1891 Nov (?) 1892 Mar 16 Confirmed 2 Historical Observations
1887 Aug 15 1889 Confirmed 2 Historical Observations Thordarhyrna
1883 Jan 15 1883 Apr 15 ± 5 days Confirmed 2 Historical Observations
1873 Jan 8 1873 Aug Confirmed 4 Historical Observations
1867 Aug 29 Unknown Confirmed 1 Historical Observations
[ 1861 May ] [ Unknown ] Uncertain 2  
1854 Unknown Confirmed 2 Historical Observations
1838 Jun Unknown Confirmed 2 Historical Observations
1823 Feb 4 ± 4 days Unknown Confirmed 2 Historical Observations Grímsvötn-Thordarhyrna
1816 May 1816 Jun (?) Confirmed 2 Historical Observations
[ 1796 Jun ] [ Unknown ] Discredited    
[ 1794 Jul 15 ± 45 days ] [ Unknown ] Uncertain    
1783 May (?) 1785 May 26 (?) Confirmed 4 Historical Observations Lakagigar (Skaftar) and Grímsvötn
1774 Feb Unknown Confirmed 2 Historical Observations
1768 Unknown Confirmed 2 Unknown
1753 Oct 15 ± 45 days Unknown Confirmed 2 Historical Observations NE of Palsfjall
1730 Unknown Confirmed   Historical Observations
1725 Feb Unknown Confirmed 2 Historical Observations
1716 Oct 6 Unknown Confirmed 2 Historical Observations
1706 Oct 15 ± 45 days Unknown Confirmed 2 Historical Observations
1697 Unknown Confirmed   Historical Observations
1684 Nov 5 ± 4 days 1685 Jan Confirmed 2 Historical Observations
1681 Apr 10 Unknown Confirmed   Uncertain
1665 Unknown Confirmed   Historical Observations
1659 Nov Unknown Confirmed 2 Historical Observations
1638 Feb 24 ± 4 days Unknown Confirmed 2 Historical Observations
1632 (?) Unknown Confirmed   Ice Core
1629 Unknown Confirmed 2 Historical Observations
1622 (?) Unknown Confirmed   Ice Core
1619 Jul 29 Unknown Confirmed 2 Historical Observations
1610 (?) Unknown Confirmed   Ice Core
1603 Oct 31 1603 Nov Confirmed 2 Unknown
1598 Nov 7 Unknown Confirmed 3 Historical Observations
1530 ± 10 years Unknown Confirmed   Ice Core
1521 (?) Unknown Confirmed   Ice Core
1510 ± 10 years Unknown Confirmed   Ice Core
1509 (?) Unknown Confirmed   Ice Core
1500 (?) Unknown Confirmed   Ice Core
1490 ± 10 years Unknown Confirmed   Ice Core
1471 (?) Unknown Confirmed   Ice Core
1470 ± 10 years Unknown Confirmed   Ice Core
1469 (?) Unknown Confirmed   Ice Core
1450 ± 10 years Unknown Confirmed   Ice Core
1430 ± 10 years Unknown Confirmed   Ice Core
1390 ± 10 years Unknown Confirmed   Ice Core
1370 ± 10 years Unknown Confirmed   Ice Core
1369 (?) Unknown Confirmed   Ice Core
1354 (?) Unknown Confirmed   Historical Observations
1350 (?) Unknown Confirmed   Ice Core
1341 May Unknown Confirmed 2 Historical Observations
1332 Nov Unknown Confirmed 2 Historical Observations
1310 ± 10 years Unknown Confirmed   Ice Core
1290 ± 10 years Unknown Confirmed   Ice Core
1270 ± 10 years Unknown Confirmed   Ice Core
1230 ± 10 years Unknown Confirmed   Ice Core
1190 (?) Unknown Confirmed   Ice Core
1150 (?) Unknown Confirmed   Ice Core
1090 (?) Unknown Confirmed   Ice Core
1060 (?) Unknown Confirmed   Tephrochronology
1010 (?) Unknown Confirmed   Ice Core
0960 (?) Unknown Confirmed   Ice Core
0910 (?) Unknown Confirmed   Tephrochronology
0050 BCE (?) Unknown Confirmed 2 Tephrochronology Halsagigur
1950 BCE ± 100 years Unknown Confirmed 2 Tephrochronology Raudholar and Brunuholar
3550 BCE ± 500 years Unknown Confirmed 0 Tephrochronology S of Thordarhyrna (Bergvatnsarhraun)
4550 BCE ± 500 years Unknown Confirmed 0 Tephrochronology Laki (Botnahraun)
8230 BCE ± 50 years Unknown Confirmed 6 Radiocarbon (corrected) Saksunarvatn tephra

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Bjornsson H, Einarsson P, 1990. Volcanoes beneath Vatnajokull, Iceland: evidence from radio echo-sounding, earthquakes and jokulhlaups. Jokull, 40: 147-168.

Brandsdottir B, 1984. Seismic activity in Vatnajokull in 1900-1982 with special reference to Skeidararhlaups, Skaftarhlaups and Vatnajokull eruptions. Jokull, 34: 141-150.

Coppola D, Staudacher Th, Cigolini C, 2005. The May-July 2003 eruption at Piton de la Fournaise (La Reunion): volume, effusion rates, and emplacement mechanisms inferred from thermal imaging and Global Positioning System (GPS) survey. In: Manga M, Ventura G (eds) Kinematics and dynamics of lava flows, {Geol Soc Amer Spec Pap}, 396: 103-124.

Gilbert J S, Stasiuk M V, Lane S J, Adam C R, Murphy M D, Sparks R S J, Naranjo J A, 1996. Non-explosive, constructional evolution of the ice-filled caldera at Volcan Sollipulli, Chile. Bull Volc, 58: 67-83.

Gronvold K, Johannesson H, 1984. Eruption in Grimsvotn 1983; course of events and chemical studies of tephra. Jokull, 34: 1-11.

Gudmundsson A T, 1986b. Iceland-Fires. Reykjavik: Vaka-Helgafell, 168 p.

Gudmundsson G, Saemundsson K, 1980. Statistical analysis of damaging earthquakes and volcanic eruptions in Iceland from 1550-1978. J Geophys Res, 47: 99-109.

Gudmundsson M T, Bjornsson H, 1991. Eruptions in Grimsvotn, Vatnajokull, Iceland, 1934-1991. Jokull, 41: 21-45.

Gudmundsson M T, Sigmundsson F, Bjornsson H, 1997. Ice-volcano interaction of the 1996 Gjalp subglacial eruption, Vatnajokull, Iceland. Nature, 389: 954-957.

Gudmundsson M T, Sigmundsson F, Bjornsson H, Hognadottir T, 2004. The 1996 eruption at Gjalp, Vatnajokull ice cap, Iceland: efficiency of heat transfer, ice deformation and subglacial water pressure. Bull Volc, 66: 46-65.

Hamilton C W, Thordarson T, Fagents S A, 2010. Explosive lava-water interactions I: architecture and emplacement chronology of the volcanic rootless cone groups in the 178301784 Laki lava flow, Iceland. Bull Volc, 72: 449-467.

Hreinsdóttir, S, Sigmundsson, F, Roberts, M J, Björnsson, H, Grapenthin, R, Arason, P, Árnadóttir, T, Hólmjárn, J, Geirsson, H, Bennett, R A, Gudmundsson, M T, Oddsson, B, Ófeigsson, B G, Villemin, T, Jónsson, T, Sturkell, E, Höskuldsson, A, Larsen, G, Thordarson, T, Óladóttir, B A, 2014. Volcanic plume height correlated with magma-pressure change at Grímsvötn Volcano, Iceland. Nature Geoscience Letters, 12 January 2014.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Jakobsson S P, 1979. Petrology of recent basalts of the eastern volcanic zone, Iceland. Acta Nat Islandica, 26: 1-103.

Jarosch A, Gudmundsson M T, Hognadottir T, Axelsson G, 2008. Progressive cooling of the hyaloclastic ridge at Gjalp, Iceland, 1996-2005. J Volc Geotherm Res, 170: 218-229.

Johannesson H, Jakobsson S P, Saemundsson K, 1982. Geological map of Iceland, sheet 6, south Iceland. Icelandic Museum Nat Hist & Iceland Geodetic Surv, 1:250,000 geol map, 2nd edition.

Johannsdottir G E, Thordarson T, Larsen G, 2004. The widespread ~10 ka Saksunarvatn tephra: a product of large-scale basaltic phreatoplinian eruption?. IAVCEI Chile Gen Assembly, Pucon 2004, abs S12_o_03.

Jonsson J, 1979b. Volcanoes and lava flows in Skaftafellssysla. Natturufraedingurinn, 48: 196-232 (in Icelandic with English summary).

Konstantinou K I, Nolet G, Morgan W J, Allen R M, Pritchard M J, 2000. Seismic phenomena associated with the 1996 Vatnajokull eruption, central Iceland. J Volc Geotherm Res, 102: 169-187.

Kristmannsdottir H, Bhornsson A, Palsson S, Sveinbjornsdottir A E, 1999. The impact of the 1996 subglacial volcanic eruption in Vatnajokull on the river Jokulsa a Fjollum, North Iceland. J Volc Geotherm Res, 92: 359-372.

Larsen G, Gudmundsson M T, Bjornsson H, 1998. Eight centuries of periodic volcanism at the center of the hotspot revealed by glacier tephrostratigraphy. Geology, 26: 943-946.

Sigmarsson O, Karlsson H R, Larsen G, 2000. The 1996 and 1998 subglacial eruptions beneath the Vatnajokull ice sheet in Iceland: contrasting geochemical and geophysical inferences on magma migration. Bull Volc, 61: 468-476.

Steinthorsson S, 1977. Tephra layers in a drill core from the Vatnajokull ice cap. Jokull, 27: 2-27.

Steinthorsson S, et al., 2002. Catalog of Active Volcanoes of the World - Iceland. Unpublished manuscript.

Thorarinsson S, 1974. The History of Grimsvotn Eruptions and Skeidara Floods. Reykjavik: Bokautgafa Menningarsjods, 254 p (in Icelandic).

Thordarson T, Self S, 1993. The Laki (Skaftar Fires) and Grimsvotn eruptions in 1783-1785. Bull Volc, 55: 233-263.

Witham C S, Oppenheimer C, 2005. Mortality in England during the 1783-4 Laki Craters eruption. Bull Volc, 67: 15-26.

Grímsvötn, Iceland's most frequently active volcano in historical time, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200-m-thick ice shelf, and only the southern rim of the 6 x 8 km caldera is exposed. The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam. Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world's largest known historical lava flow during an eruption in 1783. The 15-cu-km basaltic Laki lavas were erupted over a 7-month period from a 27-km-long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.