Glaciers advance in colder temperatures, but sometimes a big rock avalanche can also make a glacier grow, new research results presented at the American Geophysical Union’s annual meeting suggests. Using earthquake recordings and satellite images, Colin Stark, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory, says that a massive landslide hit Tajikstan’s 22,000-foot peak, Mount Garmo, in 2001, possibly explaining the glacier’s two-kilometer advance since then.
The 2001 landslide dumped 300 million tons of debris on the ice and shook the ground for 80 seconds, producing the equivalent of a magnitude 5.4 earthquake—one of the largest landslides in the last 30 years, Stark and his Lamont colleagues Goran Ekstrom and Michael Wolovick estimate. They hypothesize that all that extra rock and soil triggered a two-phase glacial surge—the biggest in the months after the slide followed by a second, five to six years later. In the first surge, heat released during the avalanche may have melted some of the ice, causing water to seep below the glacier and help it slide forward, Stark said.The mechanism for the second surge is unknown.
The landslide on Mount Garmo, in the remote Pamir Mountains, was previously thought to have occurred in 2002 but in reviewing old earthquake recordings, Stark was able to pinpoint the slide’s exact date–Sept. 2, 2001. While previous scientists speculated that an earthquake caused the slide, Stark says seasonal melting at this time was probably responsible.