One of the worlds largest ice avalanches ever recorded has flummoxed glaciologists. The slide contained about 100 million cubic metres of ice and rocks as it roared down a narrow valley killing nine herders and hundreds of sheep and yaks.
The slide occurred in the Aru Range of the Rutog county in the west of the Tibet Autonomous Region on July 17, 2016. NASA in their coverage noted that “Tian Lide, a glaciologist at the Chinese Academy of Sciences, visited the site in August and described the avalanche as “baffling” because the area where the ice collapse began is rather flat”.
The Himalaya mountains are commonly referred to as the world’s Third Pole because the glaciers of Central and South Asia, including Tibet, hold the largest reserves of glacier ice outside of Antarctica, Greenland, and Canada. The Tibetan Plateau has an average elevation of 14,000 feet above sea level. The plateau covers more than 965,000 square miles and is comparable in size to Western Europe.
The cause of the avalanche is unclear. “This is new territory scientifically,” said Kääb. “It is unknown why an entire glacier tongue would shear off like this. We would not have thought this was even possible before Kolka happened.”
Kääb’s preliminary analysis of satellite imagery indicates that the glacier showed signs of change weeks before the avalanche happened. Normally, such signs would be clues the glacier might be in the process of surging, but surging glaciers typically flow at a fairly slow rate rather than collapsing violently in an avalanche.
After inspecting the satellite imagery, University of Arizona glaciologist Jeffrey Kargel agreed that a surging glacier could not be the cause. “The form is completely wrong,” he said. “It must be a high-energy mass flow. Maybe liquid water lubrication at the base played some role,” he said.
This before-and-after image shows the ice sheet vanishing from a valley in the Aru Range of Tibet. (NASA) Credit: NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey and Sentinel data from the European Space Agency. Special thanks to Simon Gascoin for locating the images. Image interpretation assistance by Andreas Kääb (University of Oslo), Tian Lide ( Chinese Academy of Sciences), and Jeffrey Kargel (University of Arizona). Caption by Adam Voiland.Himalayas