Alaska has long been known for its sizable geological events -- particularly the 1964 magnitude-9.2 Good Friday earthquake, the second-largest ever recorded, and the 1912 eruption of Novarupta, the largest volcanic eruption of the 20th century. And earlier this month, Alaska added to the list another notable event on a massive scale, when an immense landslide tumbled loose in Southeast Alaska -- a landslide that may be the largest on Earth since 2010.
NASA managed to capture satellite photos of the landslide, which broke free from Mount La Perouse a 10,728-foot peak in the Fairweather Range in Glacier Bay National Park, on Feb. 16, releasing an estimated 68 million metric tons of debris. The scale of the slide, which stretched nearly five miles over snow-covered terrain, was visible from space. From the NASA Earth Observatory blog:
The sediment slid in a southeasterly direction, stretching across 7.4 kilometers (4.6 miles) and mixing with ice and snow in the process. The slide was triggered by the collapse of a near-vertical mountain face at an elevation of 2,800 meters (9,200 feet), according to Columbia University seismologist Colin Stark.
Stark first became aware that a landslide may have occurred when a rapid detection tool that sifts through data collected by global earthquake monitoring network picked up a signal indicative of a fairly significant event. The earthquake sensors detect seismic waves—vibrations that radiate through Earth’s crust because of sudden movements of rock, ice, magma, or debris.
The landslide was far bigger than the 2012 Lituya Mountain slide, measured at about 20 million metric tons. Stark and Columbia University colleague Goran Ekstrom also detected that slide with their newly developed monitoring system. An approximately 30 million metric ton slide occurred last August in Wrangell-St. Elias National Park.