On June 17, 2017 a rockslide ( nearly 4 million tons of earth went crashing into the sea) occurred in Karrat Fjord, Greenland and the deadly tsunami it produced caused 4 deaths and 9 injuries (23 were reported missing but were believed to be hunting at the time of the tsunami). The village itself was severely damaged when chunks of ice slammed into the sea side community.
David Petley writing for the American Geophysical Union, noted that The Arktisk Kommando, the Joint Arctic Command– have posted a series of images on their Facebook page that have resulted from reconnaissance missions over the site of the landslide.
Petley identifies the best overview of the landslide site is this one.
The landslide appears to consist of a large block failure of the bluff that has then run over the less steep lower slope. In the background of the image is the other section of distressed slope that is causing concern. Above the winglet another large landslide with a clearly defined rear scarp can be seen. The Arktisk Kommando have also posted this image of the landslide scar:-
Meanwhile, my friends at Strasburg University, Clément Hibert, André Stumpf and Jean-Philippe Malet have kindly obtained two important pieces of information that they have kindly allowed me to share. First, they have downloaded before and after images of the landslide site from the Sentinel-2 satellite:-
Importantly, this shows that the second landslide was present in the imagery in early June, which reduces the concern of imminent failure (but does not eliminate it by any means of course). The Strasbourg team have noted that the early June image also appears to show the presence of landslide deposits in the area of the main landslide, suggesting that it might have been active before the major failure event.
This data definitively answers the question as to whether the earthquake was the trigger for the landslide, or was the signal from the landslide itself. It was the latter – this signal was generated by the landslide. I am no expert on this data, so I provide the observations by Clément Hibert, who most definitely is an expert:
snip
The high-frequency seismic signal (1-20Hz) exhibits the ‘classical’ features of high-frequency signals generated by landslides (emergent onset, no phases, lots of energy in the high-frequency >1Hz). However the onset of the long-period signal (<0.1 Hz) is peculiar. The first phase, coherent and visible at other stations, is more characteristic of shear faulting. This might suggest a very fast destabilisation of the mass. This is my assumption and I think this should be more thoroughly investigated with inversion and modeling methods for example.
x xYouTube Video Greenland has been rapidly warming due to humanity’s burning of fossil fuels causing climate change feedback loops. It is clearly to soon for a lot of data at this point, but perhaps permafrost and/or the lack of buttressing around the fjord caused the cliff to slide? See More Rocks blog writes:To tell whether the island’s glacial cap will melt away any time soon, researchers are poring over old pictures and drawings for clues to its past behaviour.
With Arctic temperatures rising faster than anywhere else on Earth, Greenland is now losing about 200 billion tonnes of ice per year and raising ocean levels around the globe. Projections suggest that melting from the island might swell sea levels by 30 centimetres by the end of this century. If all Greenland’s ice melted — a possibility over the next few centuries − it would push up sea level by more than 6 metres, enough to flood coastal megacities such as New York and Miami. But the projections carry large uncertainties, in part because researchers lack basic information about Greenland’s past. Satellite data only go back 40 years, which is why Bjørk and his colleagues are poring over 180,000 photographs and other data that record how glaciers have advanced and retreated during cold and warm spells in the recent past. Their first sets of findings suggest that Greenland ice has responded more strongly to past climate changes than was previously realized. Now, the researchers are trying to unravel what factors within the oceans, atmosphere and inside glaciers control their behavior x xYouTube Video