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

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

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source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person,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

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

. It flows into the Greenland Sea. Jökulsá á Fjöllum streams over the waterfalls Selfoss, Dettifoss, Hafragilsfoss, 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, Vatnajökulsþjóðgarður ) is one of three national parks in Iceland. It encompasses all of Vatnajökull glacier and extensive surrounding areas. These include the national parks previously existing at Skaftafel ...

, 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 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 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 approximately 3.5 ...

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

Bárðarbunga Bárðarbunga (), is a stratovolcano located under Vatnajökull in Vatnajökull National Park which is Iceland's most extensive glacier. The second highest mountain in Iceland, above sea level, Bárðarbunga is also part of a volcanic system th ...

, 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 flood ...

''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 geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

. 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