Jökulsá á Fjöllum
Encyclopedia
Jökulsá á Fjöllum is the second longest river of Iceland
(206 km). Its source
is the Vatnajökull
glacier
. It flows into the Arctic Sea. Jökulsá á Fjöllum streams over the waterfalls Selfoss
and Dettifoss
, the second of which is the most powerful waterfall in Europe, and through the canyon at Jökulsárgljúfur National Park
, which was formed by the explosion of a volcano
situated directly beneath the river. Consequently the course of the river changed to fit the mountains. The gorge Ásbyrgi
was formed by the river in the shape of a horseshoe
. The park is one of four national parks in Iceland. The largest Jökulhlaups
(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 an eruption of Bárðarbunga
, the central volcano under the Vatnajökull
glacier, in the late Holocene
. The peak volume of this flood is estimated to have been 900,000m3/s of water discharge. This compares to the Amazon river
, which has an average discharge of 209,000m3/s of water.
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 7380 square kilometers.
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
(206 km). Its source
Source (river or stream)
The source or headwaters of a river or stream is the place from which the water in the river or stream originates.-Definition:There is no universally agreed upon definition for determining a stream's source...
is the Vatnajökull
Vatnajökull
Vatnajökull is the largest glacier in Iceland. It is located in the south-east of the island, covering more than 8% of the country.-Size:With an area of 8,100 km², Vatnajökull is the largest ice cap in Europe by volume and the second largest in area Vatnajökull is the largest glacier in...
glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
. It flows into the Arctic Sea. Jökulsá á Fjöllum streams over the waterfalls Selfoss
Selfoss (waterfall)
Selfoss is a waterfall in the river Jökulsá á Fjöllum in the north of Iceland which drops over some waterfalls about 30 km before flowing into Öxarfjörður, a bay of the Arctic Sea....
and Dettifoss
Dettifoss
Dettifoss is a waterfall in Vatnajökull National Park in Northeast Iceland, and is reputed to be the most powerful waterfall in Europe.It is situated on the Jökulsá á Fjöllum river, which flows from the Vatnajökull glacier and collects water from a large area in Northeast Iceland. The falls are 100...
, the second of which is the most powerful waterfall in Europe, and through the canyon at Jökulsárgljúfur National Park
Jökulsárgljúfur National Park
Jökulsárgljúfur National Park was a national park, situated in the north of Iceland around the river Jökulsá á Fjöllum. It lay to the north of the Dettifoss waterfall. On 7 June 2008, it became a part of the larger Vatnajökull National Park....
, which was formed by the explosion of a volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
situated directly beneath the river. Consequently the course of the river changed to fit the mountains. The gorge Ásbyrgi
Ásbyrgi
thumb|right|200px|The rock "island" in the centre of Ásbyrgi canyonÁsbyrgi canyon lies in the north of Iceland, about two hours' drive to the east from Akureyri. The horseshoe-shaped depression is part of the Jökulsárgljúfur National Park and measures approximately 3.5 km in length and 1.1 km across...
was formed by the river in the shape of a horseshoe
Horseshoe
A horseshoe, is a fabricated product, normally made of metal, although sometimes made partially or wholly of modern synthetic materials, designed to protect a horse's hoof from wear and tear. Shoes are attached on the palmar surface of the hooves, usually nailed through the insensitive hoof wall...
. The park is one of four national parks in Iceland. The largest Jökulhlaups
Jökulhlaup
A jökulhlaup is a glacial outburst flood. It is an Icelandic term that has been adopted by the English language. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland which are triggered by geothermal heating and occasionally by a volcanic subglacial...
(glacial floods) in Iceland are known to have occurred along Jökulsá á Fjöllum between 7100 and 2000 yr BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...
. The source of these floods were likely an eruption of Bárðarbunga
Bárðarbunga
Bárðarbunga is an Icelandic stratovolcano located under the ice cap of Vatnajökull glacier, rising to 2,009 m above sea level, making it the second highest mountain in Iceland, just about 101 m lower than Hvannadalshnjúkur....
, the central volcano under the Vatnajökull
Vatnajökull
Vatnajökull is the largest glacier in Iceland. It is located in the south-east of the island, covering more than 8% of the country.-Size:With an area of 8,100 km², Vatnajökull is the largest ice cap in Europe by volume and the second largest in area Vatnajökull is the largest glacier in...
glacier, in the late Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
. The peak volume of this flood is estimated to have been 900,000m3/s of water discharge. This compares to the Amazon river
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
, which has an average discharge of 209,000m3/s of water.
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 7380 square kilometers.
