20 May 2019
The Joffre Peak rock avalanches: new images
It is now clear that the second Joffre Peak rock avalanche last week was indeed larger by volume than the first. Images suggest that the release surface was probably an extension of the one that allowed the first landslide to occur.
Yesterday, Lindsey Nicholson tweeted a wonderful image, taken by Wilfied Braun, showing the full extent of the second landslide:-
The larger landslide source area is evident on Joffre Peak itself, and the full, chaotic, muddy track is also clear. Interestingly there does not appear to be much super-elevation on the bend, but field work will be needed to determine this for sure.
Collecting good satellite imagery of the landslide in an area with so much cloud is difficult. Simon Gascoin tweeted a Landsat 8 image of the first of the two Joffre Peak rock avalanches. Planet Labs have captured two images of the landslides, but unfortunately neither show the full track at this point. However, they do capture the upper portion of the tracks of the two rock avalanches, allowing the scale of the two to be compared:-
The very much larger scale of the second event, with its much broader track, is clear.
Meanwhile, there is some speculation that a further failure event is possible at Joffre Peak, given that the release surface appears to define another large rock block (see the image here to see the block that might detach). A collapse is not inevitable, but this would be a great monitoring project.
Planet Team (2019). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA.