A landscape in motion
In the vast wilderness of Kluane National Park and Reserve, the ice is not static. This region, part of the world's largest non-polar icefield, contains North America's highest concentration of surging glaciers. Unlike typical glaciers that creep forward steadily, these rivers of ice alternate between long periods of slow movement, known as the quiescent phase, and brief, dramatic surges where they can advance up to 100 times their normal speed.
During a surge, which can last from one to three years, the glacier's toe can advance several kilometers in a matter of months. The Steele Glacier, for instance, surged in 1966-67, moving over 1.5 billion tonnes of ice at speeds up to 15 meters per day. This rapid movement is not due to new ice accumulation but rather a rapid transfer of existing ice from a "reservoir zone" to the glacier's terminus. The mechanism is thought to be linked to the buildup of water at the glacier's base, which reduces friction and allows the ice mass to slide forward. The surface of the glacier becomes a chaotic jumble of crevasses and ice cliffs. The Donjek Glacier, for example, has surged eight times since the 1930s, with flow speeds reaching 1,500 meters per year.