In Greenland, the standard by which potential landslides are measured is the 2017 Karrat Fjord disaster. On the evening of 17 July, a section of mountainside at the mouth of the fjord gave way, releasing perhaps 51 million cubic metres of rubble, most of which fell into the water and created a tsunami that scientists reckon reached an initial height of 90 metres.
Although the wave had fallen considerably by time it reached the hamlet of Nuugaatsiaq, some 30km away, it still caused a tidal surge that created a series of six waves, the largest of which reached nine metres above the waterline. (The video below shows the progression from the first wave to the sixth and largest, which destroys the house in which the camera is set up.) Eleven homes were washed out to sea (one of which is pictured below); four people died; Nuugaatsiaq, as well as the neighbouring hamlet of Illorsuit, remain abandoned over concerns that an even larger section of the cliff could give way potentially creating a surge of up to 43 metres.
By those measures, the damage that could be caused by a section of mountainside identified in the same fjord system and 2015 and dubbed as the Kigarsima area is moderate. Estimated to be 1,250 metres long and 750 metres wide, and with a volume of perhaps 28 million cubic metres, should the Kigarsima area give way the wave it created would be somewhat smaller than the Karrat Fjord wave. Ukkusissat, located 29km away, is the most at-risk hamlet and could expect a surge of around seven metres. Qaarssut and Niaqornat, two other hamlets, are about twice as far away, but, because they would lie directly in the path of a wave, could expect surges that reached almost as far inland. Thanks to measures already taken in response to the Karrat event, they are considered to be prepared.
Geologists base much of their estimates on observations of fissures that were plainly visible in 2021 but had just started forming in 2015. This suggests that the area only began its movements within the past ten years. Even so, the fissures are already 20 metres deep in some areas and will only get larger; though located some 45km from the Karrat Fjord landslide, the Kigarsima area is part of the same fjord system and shares a similar geology, leading geologists to be able to predict that the parts that are in motion will pick up speed. Whether other factors are contributing to the slide is unknown, but thawing permafrost may be one explanation for its sudden appearance.
Another aspect that makes Kigarsima worth worrying about is that, much like the Karrat Fjord incident, should a landslide occur, there will be a high probability that it will be followed by successive landslides. Some standards were not made to be broken.
Kevin McGwin, PolarJournal
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