The world–famous Athabasca glacier is the most visited glacier in the Rockies.

The Athabasca is riddled with moulins, holes worn by melting water, which spiral down into the glacier. Year after year, rivers of meltwater rush down these holes and along the bedrock underneath. This ‘plumbing system’ and gravity are what cause the entire glacier to slide. Like a very slow moving river, the Athabasca is creeping forward of the rate of several centimetres per day.

Rocks embedded in the underside of the glacier scour the valley floor like sandpaper, undercut mountain flanks and cause landslides. As the Athabasca retreats, it leaves behind a moonscape of rocky moraines.

Sometimes, falling rocks land on top of a passing glacier. Acting like a conveyor belt, glaciers can carry huge boulders known as erratics, and deposit them far from their mountain home.

The small Alberta community of Okotoks (meaning “the rock”) holds a 10,000 year-old vestige of glacier glory days. Named after the 16,000 tonne rock that marks the Okotoks town outer limits, the big rock is the largest of thousands of glacier erratics that make up a 644 kilometre chain of rocks stretching out of the Rocky Mountains into the prairies. Carried on the back of a passing glacier, the big rock originated hundreds of kilometres away on Mount Edith Cavell near Jasper, Alberta.

Like the Columbia Icefield, geologists predict that within one hundred years, the Athabasca glacier will become an alpine meadow. But the glaciers will return – in about 5,000 years - further eroding and pulling apart the magnificent Rocky Mountains.

FACTS:

  • Walking on a glacier can be very dangerous. Dark cracks called crevasses are difficult to see and can be hundreds of metres deep.
  • The Athabasca Glacier has receded more than 1.5 kilometres in the past 125 years and has lost over half of its volume.

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The Nature of Things with David Suzuki
Glacier: A large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on earth. Moulin: A narrow hole through which water enters a glacier from the surface. They can be up to 10 metres wide and are typically found at a flat area of a glacier. Moulins can go all the way to the bottom of the glacier and can be hundreds of meters deep. Moulins are a part of a glacier's internal "plumbing" system, to carry meltwater out to wherever it may go. Moraine: An accumulation of unconsolidated debris which can occur in currently glaciated and formerly glaciated regions.They can be composed of glacial silt or large boulders. Erractics: A boulder carried on a glacier and deposited away from its place of origin. Crevasse: A deep crack or fracture in glacier ice.