Landslide stabilized glacier
In most regions of the world, glaciers are melting and retreating. For a long time, that was also true of Chile's Amalia Glacier. Until a mountain collapsed into the valley.
In recent decades, the Amalia Glacier in the southern Patagonian ice field, like many other glaciers, has lost enormous amounts of ice: its tongue has retreated by more than ten kilometers in the past 100 years. Hardly any other glacier in the region disappeared at a similar rate. But the trend only reversed after 2019, slowing the melt that later resumed for an unusual reason, as Maximillian Van Wyk de Vries of the University of Minnesota in Minneapolis and his team write in "Geology." A landslide stabilized the glacier.
Landslides occur more frequently in glacier environments: On the one hand, the ice tongues can make slopes steeper; on the other hand, they also make them more stable because they form a kind of abutment. If the ice body shrinks, this counterforce is missing, so that rock sections can fall. This sometimes has catastrophic consequences, as shown by a case in India, where more than 100 people died and infrastructure in a valley was destroyed in February 2021.
Fortunately, no one was harmed in Chile when 262 million cubic meters of rock and debris fell onto the ice. However, the glacier reacted immediately: Its glacier tongue advanced rapidly after having retreated relatively steadily before. Accordingly, the ice tongue grew again by more than 1000 meters. However, the initially greatly increased flow rate has again been significantly reduced, and in the meantime the Amalia glacier is even flowing to the sea at only half the speed it did before the event.
First, the landslide had pushed the ice downstream, so that the glacier immediately advanced and increased in size. Then, over time, sediment and rock from the landslide mass deposited where the glacier abuts the ocean. This prevented icebergs from breaking off into the ocean, effectively stabilizing the ice tongue. It is unclear, however, how long this effect lasts and whether shrinkage resumes at an accelerated rate thereafter.
For their study, Van Wyk de Vries and Co. did not have to be on site: They evaluated satellite images. Using this method, they hope to identify other landslides in the last 20 to 30 years that poured onto glaciers and influenced their development. It's work that could also help people in vulnerable mountainous regions. "The combination of glaciers and landslides can be extremely dangerous," says Van Wyk de Vries. "Glaciers can allow landslides to liquefy and flow much farther than they would have originally."
Spectrum of Science
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Originalartikel auf Spektrum.de
Titelbild: © ClaudineVM / Getty Images / iStock (Ausschnitt)
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