Sunday, September 9, 2012

Storegga Slide

The three Storegga slides are considered to be amongst the largest known landslides. They occurred in the Norwegian Sea, at the edge of Norway’s continental shelf, 100 km north-west of the Møre coast. The landslides caused a very large tsunami in the North Atlantic Ocean. Based on carbon dating of plant material recovered from sediment deposits, the latest incident occurred around 6100 BC. (8111 years ago). In Scotland, traces of the tsunami have been recorded, with sediment being discovered in Montrose Basin, the Firth of Forth, up to 80 km inland and 4 meters above current normal tide levels.

The Storegga slides have been investigated as part of the activities to prepare the Ormen Lange natural gas field, which is located on the Norwegian continental shelf. It has been determined that the triggering mechanism of the slides was likely a large earthquake, together with gases released from the decomposition of gas hydrates. One conclusion, made public in 2004, has hypothesized that the slide was caused by material built up during the previous ice age, and that a recurrence would only be possible after another ice age. A new slide in the area would trigger a very large tsunami that would be devastating for the coast around the North Sea and the Norwegian Sea.

Around the time of the last Storegga slide, geologists have identified that a land bridge existed in the area named Doggerland. Doggerland linked Great Britain with Denmark and the Netherlands across what is now the southern North Sea. Geological surveys have suggested that Doggerland was a large area of dry land that stretched from Britain’s east coast across to the present coast of the Netherlands and the western coasts of Germany and Denmark. The potential for historic dry land in the area was first discussed in the early 20th century, but intensified in 1931 when a commercial trawler began to recover the remains of land mammals, including mammoths and lions. Ancient tools and weapons were also uncovered.

Doggerland is believed to have been a land mass that included lagoons, marshes, mudflats, and beaches. It was a rich hunting ground populated by Mesolithic human cultures. The area was physically submerged through a gradual rise in sea level. It has been hypothesized that coastal areas of both Britain and mainland Europe were inundated by the tsunami triggered by the Storegga slide. The event would have had a catastrophic impact on the contemporary Mesolithic population, and separated cultures in Britain from those on the European mainland. One area of Doggerland said to have been destroyed in the Storegga slide is the island of Viking Bergen, located between modern Shetland and Norway, at the boundary of the North Sea and Norwegian Sea.

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