The image below shows the foot of the slope, Salkantay Cocha Lake and the initial part of the track:-<\/p>\n
![\"Salkantay](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/04\/20_04-Salkantay-6-scaled.jpg\")
A high-resolution SkySat satellite image of the area at the foot of the Salkantay landslide by Planet Labs. Image captured on 14 April 2020, copyright Planet Labs<\/a>, used with permission.<\/p><\/div>\n .<\/p>\n It is worth comparing this with the Google Earth image of the same area, collected in September 2019:<\/p>\n Google Earth image of the foot of the slope affected by the Salkantay landslide<\/p><\/div>\n .<\/p>\n Starting at the southeast corner, there is a new landslide deposit between the track\/path and the moraine ridge. This deposit is mostly fine-grained but with some large boulders present too. The moraine ridge has been smoothed by the passage of the landslide.\u00a0 There are two possible interpretations for this.\u00a0 Perhaps landslide has spread laterally after failure.\u00a0 This is possible but feel slightly counter-intuitive as the large boulders will have had to have undergone a major change in trajectory?\u00a0 Or perhaps there was also a failure on the slope orientated roughly north-south above the lake, which is in line with this deposit?<\/p>\n Any views?<\/p>\n The main part of the landslide has traveled almost due west into Salkantay Cocha Lake (this is sometimes termed Humantay Lake).\u00a0 The path that it took as it entered the depression, and the path it took as it left, are both clear.\u00a0 The intriguing aspect is that the amount of water in the lake appears to be essentially unchanged.\u00a0 This implies that the landslide skimmed across the surface of the lake without disturbing it.\u00a0 I find this really surprising.\u00a0 The alternative explanation, that the lake refilled after passage of the landslide, seems unlikely as there is no obvious source for this amount of water.\u00a0 The water was present in the lake on 10 March<\/a>, and reports immediately after the landslide also indicated that water was present<\/a>.<\/p>\n This is very perplexing behaviour.<\/p>\n The track of the landslide after leaving the Salkantay Cocha Lake is also clearly shown in the imagery.\u00a0 The southern margins of the track appear to me to be indicative of dust deposition:-<\/p>\n A high resolution SkySat satellite image of part of the track of the Salkantay landslide by Planet Labs. Image captured on 14 April 2020, copyright Planet Labs<\/a>, used with permission.<\/p><\/div>\n .<\/p>\n The implication is, I think, that this portion of the flow was mostly dry – i.e. it was a rock avalanche at this point, not a debris flow.\u00a0 The videos much further down the valley<\/a> appear to show a much wetter flow, which I think implies that the landslide entrained substantial amounts of of water (and probably wet sediment) as it traveled downstream.<\/p>\n These Planet Labs SkySat images<\/a> are a remarkable resource for understanding this complex landslide.\u00a0 Your thoughts on my interpretations are very welcome.<\/p>\n Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https:\/\/www.planet.com\/<\/a><\/p>\n![\"Salkantay](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/04\/20_04-Salkantay-7-scaled.jpg\")
![\"Salkantay](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/04\/20_04-Salkantay-8.jpg\")
Reference and acknowledgement<\/h4>\n