Jökulsá á Fjöllum (; "glacial river in the mountains") is the second longest river in

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 ...

(206 km). Its

source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute ...

is 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 ...

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

. It flows into the

Greenland Sea The Greenland Sea ( Danish: ''Grønlandshavet'') is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Gre ...

. Jökulsá á Fjöllum streams over the waterfalls

Selfoss Selfoss may refer to: *Selfoss (town), Iceland *UMF Selfoss, a football club based in Selfoss **Selfoss men's football **Selfoss women's football *Selfoss (waterfall), Iceland *Selfoss Airport Selfoss Airport is an airport serving Selfoss, a to ...

Dettifoss Dettifoss () is a waterfall in Vatnajökull National Park in Northeast Iceland, and is reputed to be the second most powerful waterfall in Europe after the Rhine Falls. Dettifoss is situated on the Jökulsá á Fjöllum river, which flows from ...

Hafragilsfoss Hafragilsfoss () is a waterfall in Iceland. The waterfall flows downstream from Dettifoss within the depths of the Jökulságljúfur canyon. This waterfall is also on the glacial river Jökulsá á Fjöllum, making it a powerful waterfall. The ...

, and , the second of which is the most powerful waterfall in Europe. The source of the river is in the

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 ...

, one of three national parks in Iceland. The river is located in the northeast of Iceland and forms the eastern boundary of Ódáðahraun, an extensive lava field. Its

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

is the largest in Iceland at 7,380 square kilometers. Selfoss July 2014

Glacial flooding

Dettifoss drops into the Jökulsárgljúfur canyon, a feature which, along with the

Ásbyrgi Ásbyrgi () is a Glacial landform, glacial canyon and forest in the north of Iceland, located approximately east of Húsavík on the Diamond Circle road. The horseshoe-shaped depression is part of the Vatnajökull National Park and measures ...

gorge, appears to have been formed by catastrophic glacial flooding caused by volcanic activity. The volcano in question was possibly

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 ...

, which has been identified as posing the risk of a similar event in the future.Dettifoss waterfall could be completely reformed by glacial flooding from Bárðarbunga volcano
/ref> The largest ''

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 ...

''s (glacial floods) in Iceland are known to have occurred along Jökulsá á Fjöllum between 7100 and 2000 yr BP. The source of these floods were likely eruptions of a major volcano under the Vatnajökull glacier, in the late

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

. The peak discharge of this flood is estimated to have been . This can be compared to the flow of the Amazon River, which has an average discharge of . The latest research concludes that the Jökulsárgljúfur canyon was formed by three flooding events. These key events occurred two, five and nine thousand years ago, separated by millennia of relative stability.

Glacial flooding

See also

References

Further reading