The Salkantay landslide: wonderful Planet Labs high-resolution satellite images

Back in February I wrote a series of pieces reconstructing the events that led to the huge and highly destructive debris flow in the Salkantay region of Peru.  It is clear that this event was a large landslide from the mountainside that transitioned into the debris flow.  My friends at Planet Labs have now succeeded in capturing not one but two fantastic high-resolution images of the site of the initial landslide.  The first was captured on 11 April 2020 using the SkySat instrument:-

A high resolution SkySat satellite image of the the Salkantay landslide by Planet Labs. Image captured on 11 April 2020, copyright Planet Labs, used with permission.

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The second was captured on 13 April 2020, also using the SkySat instrument:-

A high resolution SkySat satellite image of the the Salkantay landslide by Planet Labs. Image captured on 14 April 2020, copyright Planet Labs, used with permission.

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Let’s take a closer look at the source of the landslide.  An image captured by Benito Moncado of the site shortly after the landslide suggests that the initial failure was a steep wedge high in the rock mass.  This is a more detailed view of the landslide scar and the initial downslope deposit:-

Detail from the high resolution SkySat satellite image of the the Salkantay landslide by Planet Labs. Image captured on 11 April 2020, copyright Planet Labs, used with permission.

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It is worth comparing this image with the pre-failure Google Earth image of the Salkantay site:-

A Google Earth image of the site of the Salkantay landslide

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Comparison of the two images shows a long section of rock slope that has been removed by the landslide.  Interestingly, the 11 April image shows a smaller (but not insignificant) fresh landslide scar near to the crown of the landslide, and a debris trail on the snow, suggesting that some instability is still occurring.  The main (February) landslide has planed off the topography down the slope, probably indicating sliding on a joint surface.  It is worth noting that this slope is much steeper than it might appear on the satellite image (take a look at the photographs of the site in my earlier post).

I think that the behaviour of the landslide at the foot of the slope is really interesting too, but that is a matter for a future post.

Reference and acknowledgement

Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

Many thanks to Robert Simmon of Planet Labs, and to his colleagues there, for tasking the SkySat instrument and for providing the imagery.  Their help and support is hugely appreciated.