Great Gorge of Ruth Glacier is deeper than the Grand Canyon

Bradford Washburn

WHAT MAY BE THE deepest gorge in North America was measured successfully for the first time in the summer of 1992 by scientists from the Geophysical Institute of the University of Alaska, Fairbanks.

The Great Gorge of the Ruth Glacier 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 and in Yosemite National Park. The measurement includes 3770 feet of ice of the Ruth Glacier, which fills the bottom of the gorge at the foot of Mount Dickey, combined with the height of the 5200-foot vertical walls surrounding it. Devoid of ice, the walls of the gorge would rise to nearly 9000 feet, one of the greatest defiles in the world.

It may be helpful to consider the difference between a gorge and a canyon. A canyon is wider than it is deep, while a gorge is deeper than it is wide. For example, the Grand Canyon of the Colorado in Arizona drops 5300 feet from the rim to the canyon bottom, but it measures from four to thirteen miles across from the Northern to the Southern Rim. The Great Gorge of the Ruth Glacier drops about 9000 feet, but the ice measures only about a mile across from the cliffs on one side of the glacier to those on the other. The thickness of the ice was measured on the surface of the Ruth Glacier directly below the summit of 9545-foot Mount Dickey. The Moose’ s Tooth on the opposite, eastern side of the gorge rises to 10,335 feet.

The 40-mile-long Ruth Glacier drains the southeastern slopes of Mount McKinley as it flows through the granite-walled Great Gorge. Every flake of snow that falls on this flank of McKinley and the southern side of Mount Silverthrone flows downward and is squeezed through that mile-wide gorge. From the first time I saw it, I knew it had to be terribly deep, but I had to wait for 55 years to find the depth of the Great Gorge. I suspected it would be among the

deepest in the world.

On August 9, 1937, I made a photographic flight around and over Mount McKinley with pilot Estol Call of Anchorage. 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. From that moment on, I was fascinated with the Ruth Glacier.

At my instigation and with my help at gaining funding, researchers set out to find the bottom of the gorge two years ago. First, they tried to determine the total depth of the ice by using conventional ice radar instruments to measure the thickness of the Ruth Glacier. These are regularly used in Antarctica. That didn’t work, primarily because the gorge is so deep and so narrow that radar echoes bouncing off the side walls mixed with signals from the bottom and produced a confusing jumble of noise. Also, Alaskan glacial ice is warmer than that in Antarctica. It therefore contains more water, which weakened the signals. The scientists returned home with no record of the ice’s depth, but with a visceral conviction that it was very, very deep.

In 1992, the Alaskan scientists tried again. Associate Professor Keith Echelmeyer of the Geophysical Institute, graduate students Ted Clarke and Keri Petersen and research technicians Chris Larsen and Kent Swanson returned to the Great Gorge with dynamite and seismic geophones. These were planted at various spots in holes near the surface of the ice. Small explosions sent out sound waves that moved through the ice to the bottom of the gorge and bounced back to be picked up and timed by the geophones. Through this process, the scientists were able to determine the depth and shape of both the gorge and its glacier. The 9000-foot-deep gorge is U-shaped and less than a mile wide. The ice which is contained within it is in places more than 3800 feet thick—and it is significantly deeper on its west side than on its east.

It is now my hope that others will carry out more studies of the Ruth Glacier and its dramatic valley to record the depths of snow that accumulate at the head of it and to determine the rate at which the glacier flows both above and below the Great Gorge. Last summer, Dr. Echelmeyer also measured how fast the glacier flows through the Great Gorge, using a satellite-based GPS surveying method. He found that the ice moved an average of 3.3 feet per day, which is relatively fast for a glacier, much faster than the old and deteriorating Muldrow Glacier, which averaged only 0.46 feet (5.5 inches) per day during the last sixteen years.