The three Storegga Slides () are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated length of coastal shelf, with a total volume of of debris, which caused a tsunami in the North Atlantic Ocean. Description Storegga (Norwegian: Great Edge) is located at the edge of Norway's continental shelf in the Norwegian Sea, north-west of the Møre coast. In around 6200 BCE, structural failures of the shelf caused three underwater landslides, which triggered very large tsunamis in the North Atlantic Ocean. The collapses involved an estimated length of coastal shelf, with a total volume of of debris. Based on carbon dating of plant material recovered from sediment deposited by the tsunamis, the latest incident occurred around approximately 6225–6170 BCE. In Scotland, traces of the subsequent tsunami have been recorded, with deposited sediment being discovered in Montrose Basin, the Firth of Forth up to inland and above current normal tide levels. Possible mechanism A possible triggering mechanism is thought to have been an earthquake that induced a catastrophic expansion of methane clathrate, a solid compound consisting of large amounts of methane suspended within a crystal water structure that forms in deep oceans under extremely high pressure. If removed from a high-pressure, low-temperature environment, one cubic metre of solid methane clathrate expands to 164 cubic metres of gaseous methane. If such an expansion occurred, it may have weakened the integrity of the surrounding rock sufficiently to trigger the slide. Another theory is that over time, streams from melting glaciers had carried trillions of tons of sediment to the edge of the continental shelf, where it accumulated in many layers. In this case, a trigger such as an earthquake could have caused a large area of seafloor to collapse into the deep Norwegian sea, thus carrying the enormous volume of accumulated sediment along with it. Impact on human populations At, or shortly before, the time of the Second Storegga Slide, a land bridge known to archaeologists and geologists as Doggerland linked Britain, Denmark and the Netherlands across what is now the southern North Sea. 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 human cultures. Although Doggerland was permanently submerged through a gradual rise in