Grímsvötn (; ''vötn'' = "waters", singular: ) is an

active volcano An active volcano is a volcano that is currently erupting, or has the potential to erupt in the future. Conventionally it is applied to any that have erupted during the Holocene (the current geologic epoch that began approximately 11,700 years ...

with a (partially subglacial) fissure system located in

Vatnajökull National Park Vatnajökull National Park ( ) is one of three national parks in Iceland, and is the largest one. It encompasses all of Vatnajökull glacier and extensive surrounding areas. These include the national parks previously existing at Skaftafell in th ...

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. The

central volcano A central volcano is a type of volcano formed by basalts and silica-rich volcanic rocks. They contain very few or no volcanic rocks of intermediate composition, such that they are chemically bimodal volcanism, bimodal. Large silicic eruptions at c ...

is completely subglacial and located under the northwestern side of the

Vatnajökull Vatnajökull ( Icelandic pronunciation: , literally "Glacier of Lakes"; sometimes translated as Vatna Glacier in English) is the largest and most voluminous ice cap in Iceland, and the second largest in area in Europe after the Severny Island i ...

ice cap. The subglacial

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

is at , at an elevation of . Beneath the caldera is the

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...

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 Laki () or Lakagígar (, ''Craters of Laki'') is a volcanic fissure in the western part of Vatnajökull National Park, Iceland, not far from the volcanic fissure of Eldgjá and the small village of Kirkjubæjarklaustur. The fissure is proper ...

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 Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions conta ...

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 A jökulhlaup ( ) (literally "glacial run") is a type of glacial outburst flood. It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floo ...

. 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,

geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...

s 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 Route 1 or the Ring Road ( or ) is a national road in Iceland that circles the entire country. As a major trunk route, it is considered to be the most important piece of transport infrastructure in Iceland as it connects the majority of towns ...

) was closed when the burst occurred. A section of road across the

Skeiðará Skeiðará () is a relatively short glacier river (about 30 km long). It has its source on the glacier Skeiðarárjökull, one of the southern arms of the Vatnajökull in the south of Iceland. In spite of its short length, this river has a ...

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 Gjálp () is a hyaloclastite ridge (tindar) in Iceland under the Vatnajökull glacier shield. Its present form resulted from an eruption series in 1996 and it is probably part of the Grímsvötn volcanic system.Snæbjörn Guðmundsson: ''Vega ...

'' The Gjálp

fissure vent A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilo ...

eruption in 1996 revealed that an interaction may exist between

Bárðarbunga Bárðarbunga (, alternative name Veiðivötn), is an active and productive stratovolcano located under Vatnajökull in Vatnajökull National Park which is Iceland's most extensive glacier. The second highest mountain in Iceland, above sea le ...

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 Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

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 tremor A harmonic tremor is a sustained release of seismic and infrasonic energy typically associated with the underground movement of magma, the venting of volcanic gases from magma, or both in volcanoes, and with repetitive stick-slip or other impulsi ...

s were recorded twice around Grímsvötn on 2 and 3 October 2010, possibly indicating an impending eruption. At the same time, sudden

inflation In economics, inflation is an increase in the average price of goods and services in terms of money. This increase is measured using a price index, typically a consumer price index (CPI). When the general price level rises, each unit of curre ...

was measured by

GPS The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

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 Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

, an eruption began, with high plumes accompanied by multiple

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, Until 25 May, the eruption scale had been larger than that of the 2010 eruption of

Eyjafjallajökull Eyjafjallajökull (; "glacier of (the mountain) Eyjafjöll"), sometimes referred to by the numeronym E15, is one of the smaller ice caps of Iceland, north of Skógar and west of Mýrdalsjökull. The ice cap covers the caldera of a volcano wi ...

. 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 IcelandEurocontrol news
/ref> commenced on 22 May, followed by Greenland, Scotland, Norway,

Svalbard Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...

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

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 Icelandic Meteorological Office (IMO; ) is Iceland's national weather service and as such a government agency under the Ministry of Environment and Natural Resources. It is also active in volcano monitoring, esp. volcano seismology, and, toget ...

(IMO) issued a warning that an eruption might take place in the coming weeks or months, following scientists reporting high levels of

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...

, 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 . 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 earthquake.

Eruption history before 1990

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. The Laki eruptions which were both effusive and explosive between June 1783 and February 1784, produced the Skaftáreldahraun lava flows, which cover a large part of south-east Iceland. Before this the tip of the Rauðhólar-Eldgígur fissure system was active with the production of the 4550 BCE Botnahraun lava flow which extends beyond the furtherest extent to the south of the Laki lava field. The Rauðhólar-Eldgígur fissure system also formed the Núpahraun lava flows around 4000 that extend from the Vatnajökull glacier towards the south east coast and are covered in part by the northern Laki Skaftáreldahraun lava flow. There are two recent pre-historic but undated Bergvatnsárhraun lava flows just on the south-eastern edge of the Vatnajökull glacier, related to the line of the Rauðhólar-Eldgígur fissures.

Bacteria in the subglacial lakes

In 2004, a community of

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

was detected in water of the Grímsvötn lake under the glacier, the first time that bacteria have been found in a subglacial lake. The lakes never freeze because of the volcanic heat. The bacteria can also survive at low concentrations of

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

. The site is a possible analogue for life on the

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

, because there are also traces of volcanism and glaciers on Mars and thus the findings could help identify how to look for life on Mars.

Geology

There is the potential for mechanical interaction such as dyke propagation between Grímsvötn and Thordarhyrna. Interactions can also occur with the nearby

volcano, which is part of a separate volcanic system. The volcano erupts predominantly

tholeiitic basalt The tholeiitic magma series () is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic ...

, and a close chemical affinity exists with the other lavas of the Grímsvötn-Laki 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. Some of the tephra's erupted have transpired to have mixed compositions with nearby volcanic systems and it is not known if this is due to dual eruptions or intusions crossing magma reserviors. The volcanic system is part of the Eastern volcanic zone of Iceland, and is directly over the Iceland mantle plume. The volcanic system has crater rows extending to the south east; the long Laki–Grímsvötn fissure system and the long Rauðhólar-Eldgígur fissure system. The Rauðhólar-Eldgígur fissure system has been related by some authors to an alignment with the Thordarhyrna central volcano with the Laki–Grímsvötn more in alignment with the Grímsvötn central volcano. Eruptives from Grímsvötn and Thordarhyrna are able to be geochemically distinguished between, so it is possible that the two central volcanoes are not one system. Thordarhyrna has rhyolite formations which have not been found at Grímsvötn.

Future trends

Studies indicate that volcanic activity in Iceland rises and falls so that the frequency and size of eruptions in and around the Vatnajökull ice cap varies with time. It is believed that the four eruptions between 1996 and 2011 could mark the beginning of an active period, during which an eruption in Grímsvötn in Vatnajökull may be expected every 2–7 years. Parallel volcanic activity in nearby

is known to be associated with increased activity in Grímsvötn. Seismic activity has been increasing in the area in recent years, indicating the entry of magma.

Notes

References

External links

Grímsvötn
in the Catalogue of Icelandic Volcanoes
Update on Grímsvötn Activity
– from the Icelandic Met Office and University of Iceland (updated at least daily)
Current seismology around Grímsvötn
– Earthquakes in last 48 hours
BBC news report of the 23 May 2011 eruption

Report on the 2011 start of the Grímsvötn eruption
from the Icelandic Met Office
Official Website of Vatnajökull National Park
{{DEFAULTSORT:Grimsvotn Active volcanoes Highlands of Iceland Subglacial volcanoes of Iceland Volcanoes of Iceland VEI-6 volcanoes Subglacial lakes Lakes of Iceland East Volcanic Zone of Iceland Volcanic systems of Iceland Subglacial calderas Calderas of Iceland Jökulhlaups