A long run out landslide from Yudi Peak in Alaska

With thanks from me to loyal reader Hig for pointing it out, the Facebook page of Alpine Air Alaska has some stunning photographs, and a very cool video, of a long run out landslide that has recently occurred on Yudi Peak, near to Girdwood in Alaska.  This is one of their images:-

The upper reaches of the landslide from Yudi Peak in Alaska. Image from the Facebook Page of Alpine Air Alaska.

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The crown of the Yudi Peak landslide is located at 61.03, -148.96 at an elevation of about 1430 m. It has a run out distance of about 2 km, stopping at an elevation of about 1009 m. This image, also posted to the Facebook Page of Alpine Air Alaska, shows the full length of the landslide:-

The full extent of the landslide from Yudi Peak in Alaska. Image from the Facebook Page of Alpine Air Alaska.

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From the images, that landslide appears to have initiated as a wedge failure.  The volume is not very large. but the terrain is steep and the initial sliding surface was snow and ice, providing a high level of mobility.  There may have been some entrainment once the landslide reached the bedrock areas. The best view of the landslide is on a video that Alpine Air Alaska have flown of the full length of slide.  It is very rare to have such good coverage of the full track of a slide.

The landslide is first visible on satellite imagery on 10 May 2020. It is not visible on an image on 6 May 2020, so it occurred sometime in that window.

It is well established that Alaska sees large landslides in the Spring, and that their increasing size and frequency is driven by global heating.

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On reflection 1: landslide threat from Cyclone Amphan

Cyclone Amphan is now an extremely dangerous tropical cyclone, tracking northwards to make landfall, probably in West Bengal, tomorrow.  Whilst it will weaken a little in the next 24 hours, it has the potential to cause very substantial levels of damage, compounded of course by the increased vulnerability of the population as a result of Covid-19. This storm will bring extreme rainfall to the hilly areas of Bangladesh, NE India and possibly E. Bhutan.  The potential for severe landslides and floods is high.

The ever wonderful Save the Hills blog, which features community efforts to manage landslides in the Kalimpong area on NE India, is likely to feature some of the impacts.  I await the outcome of this storm with some trepidation – expect news of landslides towards the end of the week.

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On reflection 2: landslides from a Mw=5.2 earthquake in China

At 13:48 UTC a Mw=5.2 earthquake struck Qiaojia County in Yunnan Province, China. Xinhua reports four fatalities so far, and at least some landslide impacts:

Xinhua reporters on Tuesday morning saw rescuers approaching Yakou Village, Xiaohe Township in the epicenter of Qiaojia. Excavators are removing debris of landslides along the road.