A landslide at Kråknes in Finnmark County, northern Norway, has swept a cluster of houses into the sea. The incident happened at about 4.00 pm local rime on Wednesday 3 June 2020, when a section of land 600 m wide and 150 m deep shifted downslope abruptly, carrying with it eight houses. The land remained reasonably intact for most of the slip, but broke up as it came to the top of the beach below, destroying the structures upon it. The majority of the buildings were unoccupied at the time of the incident, as they were holiday homes only occupied at the weekends at this time of year, though one person had to be rescued by helicopter.
Landslide at Kråknes in Finnmark County, northern Norway, on 3 June 2020. Around Zeeworld/YouTube.
The landslide is thought to have been of a type known as a 'quick clay' landslip, in which an entire bedding plain of clay loses its cohesion at once, and flows like a liquid, a type of landslide largely peculiar to areas of heavy Pleistocene glaciation, such as the northern coasts of Scandinavia, Russia, Alaska and Canada. Quick clay deposits were laid down in areas where the land was pushed down beneath sealevel by the weight of glaciers, and has subsequently been uplifted after the glaciers retreated. These clays typically contain far higher salt contents than other marine clays, which can be washed out by rainfall. Significantly, they generally contain significant levels of positively charged sodium cations, which entered the clay as the sea above froze, and help to bond the negatively charged clay particles together. However, sodium particles are particularly soluble in water, and easily washed out, with the effect that once a certain level of sodium has been lost, the entire bedding plane loses its cohesion.
The aftermath of the 3 June 2020 Kråknes landslide. The Weather Channel.
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