Scientists say they've discovered a giant landslide in an uninhabited area of eastern Alaska that's the largest detected in North America since the 1980 eruption of Mount St. Helens.

Columbia University's Lamont-Doherty Earth Observatory says the Oct. 17 slider unleashed 200 million tons of rock on Tyndall Glacier in Icy Bay.

No one witnessed the slide, but Lamont officials say the scientists picked up its "seismic signature" with a method of reading data patterns they've been honing for six years.

Officials say the landslide was confirmed by satellite images. The discovery of the landslide was announced Friday in San Francisco at the American Geophysical Union meeting.

Lamont geomorphologist Colin Stark says the Mount St. Helens eruption in Washington state accounted for a 2.5 billion ton landslide from a flank collapse.