Public Information and Education Outreach Office

The Great Gorge at Mount McKinley is deeper than the Grand Canyon
(from a press release written by the Geophysical Institute Public Information and Education Outreach Office)

What may be the deepest gorge in North America, and possibly the world, was measured successfully for the first time in 1982 by scientists from the Geophysical Institute.

The "Great Gorge," located on the south side of Mount McKinley, was found to be nearly 9000 feet deep, making it deeper than the steepest valleys in the Grand Canyon or Yosemite National Park. The measurement includes the ice of the Ruth Glacier, which fills the bottom of the gorge, combined with the height of the vertical walls surrounding it.

The 40-mile-long Ruth Glacier drains the southern slopes of Mount McKinley as it flows through the granite-walled Great Gorge. Impressive mountains such as Moose's Tooth, Mount Dickey, the Shield, and Rooster Comb rise up along its sides. Most of the Ruth Glacier is located within Denali National Park and Preserve.

Commissioned by Bradford Washburn, honorary director of the Boston Museum of Science, researchers set out to determine the total depth of the Great Gorge by using conventional ice radar instruments to measure the thickness of Ruth Glacier. That method didn't work because the ice in the gorge was too thick for standard instruments to penetrate.

Geophysical Institute Associate Professor Keith Echelmeyer had another plan. He and a crew consisting of GI research associates Ted Clarke, Carol Petersen and Chris Larsen returned to the gorge with seismic instruments, some of which triggered small explosions powerful enough to send seismic waves through the Ruth Glacier to the bottom of the gorge.

Through this process, the scientists were able to determine the depth and the shape of the gorge and the glacier. The 9000-foot-deep gorge is U-shaped and less than a mile wide at the top; the ice contained within it is more than 3800 feet thick.

Washburn, who has mapped both Mount McKinley and Mount Everest, said he's been waiting for 55 years to find out the depth of the Great Gorge. He suspected it would be among the deepest gorges in the world.

"Every flake of snow that falls on the southeastern flanks of Mount McKinley pours downward and is squeezed through that mile-wide gorge," Washburn said during a recent telephone interview from Boston. "I knew the gorge had to be very, very, very deep."

Washburn has done extensive studies on the Muldrow Glacier on Mount McKinley and was responsible for designing a detailed large-scale map of the area in 1960. During his studies, Washburn became fascinated with the nearby Ruth Glacier.

"On August 9, 1937, I made a photographic flight around and over Mount McKinley," Washburn said. "It was on that flight that I got my first glimpse of the Great Gorge and it was an experience I'll never forget. The Ruth is McKinley's most spectacular glacier and the wilderness through which it flows is the most dramatic in North America."

Washburn hopes others will finance more studies on the Ruth Glacier above and below the Great Gorge to record the depths of snow that accumulate at the head of the glacier and to determine the rate at which the glacier melts and flows. Echelmeyer already has measured how fast the glacier moved through the Great Gorge. Using a satellite-based surveying method, he estimates that the ice moves an average speed of 3.3 feet per day, which is relatively fast for a glacier.