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There has been a lot of confusion in the past 24hrs surrounding the term 'glacier burst' and exactly what happened to cause the #UttarakhandDisaster flood. Analysis by myself and colleagues suggested a landslide that took out part of a hanging glacier. 1/n https://twitter.com/davepetley/status/1358801445575917570
I'd like to clear up some terminology: 'glacier burst' is not a thing (looking at you @CNN & others). It's possible someone somewhere said glacial lake outburst flood (GLOF) which IS a thing, and that got miscommunicated in the media, but we don't think a GLOF was responsible 2/n
The glacier that we think collapsed is a very steep, hanging glacier. It is not a typical valley glacier, with low gradient/slope, that sometimes have lakes at the terminus. 3/n https://twitter.com/WaterSHEDLab/status/1358437031802593280?s=20
So this landslide probably contained both bedrock as well as glacier ice. It descended a steep slope and likely disintegrated when it hit the valley floor. This is where things get interesting, scientifically. 4/n https://twitter.com/CScottWatson/status/1358477839281102850?s=20
The site also saw an earlier landslide in 2016 that may have deposited glacial ice in the valley and when covered with debris, had not yet melted. This COULD have provided a source for the water that we see in the videos. I say could because the vids show a LOT of water. 5/n
The source of the water is still an open question that many of us in the landslide/geohazards community are trying to figure out. But statements such as "There was no landslide or avalanche" are demonstrably false. 6/n https://www.hindustantimes.com/india-news/breach-avalanche-cause-of-flood-divides-scientists-101612808514904.html
The idea that a subglacial lake at Nanda Devi may have burst is indeed a possibility. There is likely an overdeepening under the glacier that could store a lot of water to generate a flood. But so far anyway, I see no evidence of this having happened. 7/n
These 2 @planetlabs images from Feb 6 and 8 of the terminus of Nanda Devi Glacier. I don't see any evidence of a flood emanating from here. If there is some evidence from aerial surveys or other, I would be VERY interested to see it. END.
