Storegga Slide
The three Storegga Slides are considered to be amongst the largest known landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

s. They occurred under water, at the edge of Norway's continental shelf (Storegga is Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...

 for "the Great Edge"), in the Norwegian Sea
Norwegian Sea
The Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea and the Greenland Sea and adjoins the North Atlantic Ocean to the west and the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a...

, 100 km north-west of the Møre
Møre is the name of two traditional districts in different parts of Scandinavia.*Møre og Romsdal, Norway.*Möre, Sweden....

 coast, causing a very large tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 in the North Atlantic Ocean. This collapse involved an estimated 290 km length of coastal shelf, with a total volume of 3,500 km3 of debris. This would be the equivalent volume to an area the size of 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...

 covered to a depth of 34 meters (111.5 ft).

Based on carbon dating of plant material recovered from sediment deposited by the tsunami, the latest incident occurred around 6100 BC. In Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, traces of the subsequent tsunami have been recorded, with deposited sediment being discovered in Montrose Basin
Montrose Basin
The Montrose Basin is part of the estuary of the South Esk forming a tidal basin near to the town of Montrose, Angus, on the north-east coast of Scotland....

, the Firth of Forth
Firth of Forth
The Firth of Forth is the estuary or firth of Scotland's River Forth, where it flows into the North Sea, between Fife to the north, and West Lothian, the City of Edinburgh and East Lothian to the south...

, up to 80 km inland and 4 metres above current normal tide levels.

As part of the activities to prepare the Ormen Lange natural gas field, the incident has been thoroughly investigated. One conclusion is that the slide was caused by material built up during the previous ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

, and that a recurrence would only be possible after a new ice age.

Facts and arguments supporting this conclusion were made public in 2004. Earlier it was concluded that the development of the Ormen Lange gas field would not significantly increase the risk of triggering a new slide. A new slide would trigger a very large tsunami that would be devastating for the coast areas around the North Sea and the Norwegian Sea.

Possible mechanism

Earthquakes, together with gases (e.g. methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

) released from the decomposition of gas hydrates, are considered to be the likely triggering mechanisms for the slides. Another possibility is that the sediments became unstable and failed perhaps under the influence of an earthquake or ocean currents.

Impact on human populations

At, or shortly before, the time of the last Storegga Slide, a land bridge
Land bridge
A land bridge, in biogeography, is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonise new lands...

 known to archaeologists and geologists as "Doggerland
Doggerland is a name given by archaeologists and geologists to a former landmass in the southern North Sea that connected the island of Great Britain to mainland Europe during and after the last Ice Age, surviving until about 6,500 or 6,200 BCE, though gradually being swallowed by rising sea levels...

" existed, linking Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 with Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 and the Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 across what is now the southern North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

. This area is believed to have included a coastline of lagoons, marshes, mudflats, and beaches, and to have been a rich hunting, fowling and fishing ground populated by Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....

 human cultures. Although Doggerland was physically submerged through a gradual rise in sea level, it has been suggested that coastal areas of both Britain and mainland Europe, extending over areas which are now submerged, would have been inundated by a tsunami triggered by the Storegga Slide. This event would have had a catastrophic impact on the contemporary Mesolithic population, and separated cultures in Britain from those on the European mainland.

See also

  • Tsunamis in the United Kingdom
  • Arctic methane release
    Arctic methane release
    Arctic methane release is the release of methane from seas and soils in permafrost regions of the Arctic, as part of a more general release of carbon from these soils and seas. Whilst a long-term natural process, it may be exacerbated by global warming. This results in a weak positive feedback...

  • Methane clathrate
    Methane clathrate
    Methane clathrate, also called methane hydrate, hydromethane, methane ice, "fire ice", natural gas hydrate or just gas hydrate, is a solid clathrate compound in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice...

  • Viking Bergen Island
    Viking Bergen Island
    Viking Bergen is the name of a hypothetical former island between modern Shetland and Norway, at the boundary of the North Sea, and Norwegian Sea. The area is now known as the "Viking-Bergen banks"....

External links

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