Satellite images before Nepal disaster showed warning signs

Manoochehr Shirzaei, a geophysicist at Virginia Tech in Blacksburg, says that satellite images from just days before the disaster suggest that a section of the glacier and the rocks it sat on top of were accelerating in the weeks before the collapse, a concerning sign of an unstable system. The precise sequence of events remains unclear. The disaster might have begun with a massive rockslide that dragged part of the glacier downhill, or the glacier might have failed first, causing rocks to destabilize into a landslide.

[...]

It was particularly difficult to anticipate because it seems to have originated from the sudden failure of a high-elevation glacier–rock system, rather than a more routinely monitored trigger, such as extreme rainfall or the gradual rise of water in a known glacial lake. These high-mountain areas are remote, difficult to access and generally lack continuous monitoring with ground-based instrumentation.

[...]

We detected evidence that the glacier–rock system was slowly moving downhill near the apparent collapse area, with velocities reaching roughly 10 millimetres per month. Glaciers can move at speeds of roughly 10–200 metres per year, so a slope moving steadily at 10 mm a month for years might not seem particularly alarming.

[...]

What is still largely missing is a regional satellite-based system that routinely searches for accelerating glacier and rock-slope deformation and then connects that information directly to downstream flood and avalanche modelling.

[...]

But detecting an unstable glacier is only half of the problem. The system would also have to determine what happens if it fails. A relatively small collapse in an isolated basin might pose little downstream risk. A similar collapse that enters a confined valley, blocks a river and creates a temporary lake could produce a devastating cascade event.

[...]