On December 6, 2025, a powerful magnitude 7.0 earthquake struck the remote St. Elias Mountains, a highly glaciated range that spans the Yukon-Alaska border. The quake shook the landscape beneath Hubbard Glacier, sending ice and rock careening down the range’s steep slopes. The NISAR (NASA-ISRO Synthetic Aperture Radar) satellite offered some of the earliest views of the changed landscape.
Geophysicist Eric Fielding and colleagues at NASA’s Jet Propulsion Laboratory (JPL) typically use satellite data to map the displacement of the ground after major earthquakes strike land. But in this region, such maps—known as interferograms—are not possible because the ground lies buried beneath a layer of glacial ice that’s at least 700 meters (2,000 feet) thick. “The cryosphere is covering up the geosphere,” Fielding said.
Instead, clues to the earthquake’s destructive power lay strewn atop the ice surface. The shaking on December 6 unleashed landslides and avalanches that swept debris onto lower, flatter stretches of the glacier. The debris is visible in radar imagery acquired by NISAR on December 8, two days after the quake (right). For comparison, the NISAR image on the left shows the same area on November 26, a week and a half before the quake.
Where the slides have deposited rock, snow, and other debris, surfaces have become rougher, which scatters more energy back toward the sensor and makes those areas appear bright in the December 8 image (the roughest areas are shown in dark green). Areas with smooth surfaces reflect little of the rada …