Glacier avalanches more common than thought

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Published on 3 May 2021

One tends to think of mountain glaciers as slow moving, their gradual passage down a mountainside visible only through a long series of satellite imagery or years of time-lapse photography. However, new research shows that glacier flow can be much more dramatic, ranging from about 10 metres a day to speeds that are more like that of avalanches, with obvious potential dire consequences for those living below.

Glaciers are generally slow-flowing rivers of ice, under the force of gravity transporting snow that has turned to ice at the top of the mountain to locations lower down the valley – a gradual process of balancing their upper-region mass gain with their lower-elevation mass loss. This process usually takes many decades. Since this is influenced by the climate, scientists use changes in the rate of glacier flow as an indicator of climate change.

For some glaciers around the world this gradual flow can speed up, so that they advance several kilometres in just a few month or years, a process called glacier surging. After a surge, the glacier usually remains still and the displaced ice melts over a few decades.

Glacier avalanches in the Sedongpu region, China

Although surges can block rivers and create lakes that may burst suddenly, these events don’t often pose any danger, as by their very nature, they tend to be in remote and sparsely-populated regions – a fact that means that these events are often only known about thanks to data and images from satellites.

For several years now, scientists have known that a glacier can also actually detach from the mountain rock and gush down to the valley at speeds of up to 300 kilometres an hour as a fluid ice-rock avalanche.

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