Alaska cliff collapse creates largest landslide in U.S.

ANCHORAGE, Alaska – Even by Alaska standards, the rock slide in Glacier Bay National Park was a huge event.

It was a monumental geophysical event that was almost overlooked until a pilot happened to fly over where the cliff collapsed and snapped some photographs nearly a month later.

When the cliff collapsed in the national park in southeast Alaska on June 11, it sent rock and ice coursing down a valley and over a lovely white glacier in what perhaps was the largest landslide recorded in North America.

The rumbling was enough so that it showed up as a 3.4-magnitude earthquake in Alaska. The massive landslide occurred in a remote valley beneath the 11,750-foot Lituya Mountain in the Fairweather Range about six miles from the border with British Columbia.

“I don’t know of any that are bigger,” Marten Geertsema, a research geomorphologist for the provincial Forest Service in British Columbia, said Thursday, when comparing the landslide to others in North America.

Despite the extraordinary size of the landslide, which was estimated at a half-mile wide and 5 1/2 miles long, it went virtually unnoticed until air taxi pilot Drake Olson flew over it on July 2. The landslide, which rolled over the glacier, is not very noticeable to the thousands of cruise ship passengers that visit Glacier Bay National Park near Juneau each summer. That is because it is about 12 to 15 miles up the glacier from the bay.

While this one was huge by North American standards, bigger ones have occurred, including a September 2002 landslide in Russia that extended for 20 miles, Geertsema said.