11 September 2017
A dramatic earthflow video from Dimye village in Tibet
Posted by Dave Petley
A dramatic earthflow video from Dimye village in Tibet
A video has been circulating this weekend on Twitter showing a dramatic earthflow from Dimye in Tibet. This apparently originated from Wechat & Weibo in China, although very little information is available about it. This is the Youtube version:-
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The accompanying text for the video associated it with melting permafrost. On Twitter, Mika McKinnon (@mikamckinnnon) has undertaken a huge amount of background work on this event, and has identified the location as Dimye village, Zatoe (Zaduo in Chinese) township, Tridu county, Yushu prefecture, Qinghai Province. The landslide occurred on 7th September 2017. She also found an additional video of the landslide on Facebook.
Whilst the posting links this event to permafrost degradation, this is not clear to me. This image, from the second video, shows the materials involved in the landslide:-
A still from a Facebook video showing the earthflow at Dimye in Tibet.
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The video does not showing any obvious frozen soil or ice blocks. To me this is quite reminiscent of the landslides that we see in peat in the uplands of Europe. My fellow blogger Callan Bentley featured a nice example on his blog exactly a year ago. The soils involved in the Dimye village landslide are extremely dark in colour, which suggests that they are rich in organic matter. I note that in a recent (open access) paper, Yang et al. (2017) describe peat areas in the Qinghai-Tibetan area, noting that there is significant environmental degradation occurring in these places, causing rapid peat loss.
It is not possible to say whether this is indeed a peat landslide, or something similar in an organic soil, or a permafrost slide. Unfortunately, I doubt that more information will become available in the near future. But it is a great video.
Reference
, , , , , , , , , , , , , and . 2017. Qinghai–Tibetan Plateau peatland sustainable utilization under anthropogenic disturbances and climate change. Ecosystem Health and Sustainability 3 (3):e01263. doi: 10.1002/ehs2.1263
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
An observation: The debris flow, for that is what it is, is so controlled. It is relatively slow in movement under gravity, has an apparent stable height of around 2 mH, and does not give cause for itself to go ‘houncy bouncy’, laterally.
The following are relevant questions
Is this an annual event? Or a ‘one off’, at that particular locations.
Cf. to the PEAT flows of Europe.
There is a restraining shear between the base of the flow and the G.L. The flow is similar to the great floods in NSW, (Australia) in which on account of low So, (the slope), the flood will take days to move.
But here So is relatively mild for a mountain slope. Compare to the great rockfalls under mountain orogenics of Mt. Adams, Westland, N.Z.
[Many thanks. Definitely not an annual event, this is a one-off. I suspect a large mass failed in the source area and the landslide has entrained en route. The constant velocity suggests to me that the stress state and material properties are not changing. I suspect that this will have continued until eithe the gradient or the material change. The low angle of the slope is key, as you say. These conditions are similar to those that we see in the peatland areas of northern Europe. D.]