19 January 2021
A sensational high resolution satellite image of the Mount Silberhorn rock avalanche
On 31 December 2020 pilots from Mount Cook Ski Planes & Helicopters in New Zealand posted images of the aftermath of a large rockslide from Mount Silberhorn in New Zealand. Mount Silberhorn, with an elevation of 3303 m, is the fifth highest peak in New Zealand. It is located near to Aoraki/Mt Cook in the Southern Alps.
My friends at Planet Labs have very kindly collected a high resolution SkySat image of the landslide – and oh my, what an image this is:-
Clearly the source of the landslide is in the northwest of the image, with the slide moving towards the east and south. Note the clearly evident rock avalanche phase in the early part of the track – the image also picks up the dust staining of the snow around the landslide from this phase. In the lower part of the track the movement has transitioned into sliding, and there are the finger-like structures at the toe that might be associated with slow creep sliding at the end of the movement.
On the steep slopes of Mount Silberhorn there are a small number of separate landslides – one is toe the immediate south of the source area, with the debris moving towards the south. There are at least two others in this area. It is possible that these were triggered by the same process as for the main Mount Silberhorn rock avalanche, but I suspect that it is more likely that these were induced by the vibrations from the main landslide.
Perhaps the most remarkable thing about this image, which was captured on 12 January 2021, is that there is no post-event snowfall onto the landslide. This allows the features to be seen with ease.
Reference and acknowledgement
Planet Team (2021). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
Thanks to Robert Simmon and his colleagues at Planet Labs for collecting this wonderful image.