Canadian Geographic
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This water-rich land

Glaciers


Glaciers are flowing rivers of land ice, which originate with the accumulation and compression of snow. In the arctic climate of Ellesmere Island, glaciers overlay the land as they once did when they covered all of Canada. During the last 2 million years, ice swept over Canada four times.

The ice retreated during warmer periods, including our present time. At the zenith of the last advance, 18,000 years ago, the Laurentide Ice Sheet extended beyond the Canadian Shield to depths of three kilometres. In the West, the Cordilleran Ice Sheet stretched from the Rockies to the Pacific. The slow but relentless movement of ice scoured the face of Canada, leaving behind landmarks such as drumlins, eskers, and moraines. The only remnant from the distant icy past is the 100,000-year-old Barnes Ice Cap on Baffin Island. Today, three-quarters of Canada’s glaciers cloak parts of the eastern Arctic islands. The remaining glaciers cap the alpine summits of the Rockies and the West Coast ranges. In all, Canada’s glaciers cover 200,000 square kilometres — roughly half the area of Newfoundland and Labrador.

Some 12,000 years ago, meltwater of a glacier and an ice-dammed lake flowed from tunnels into streams, depositing mud, sand, and gravel. This debris, known as till, spread over the outwash plain where ice blocks fill steep-sided potholes. The glacial-lake bottom is now fertile land. Drumlins are hills composed of till; eskers, ridges of gravel and sand that were once the bed of meltwater streams. Kettle lakes fill the potholes after the ice blocks melt.

Synopsis

Rivers of ice A video launches automatically within a box, entitled “Rivers of ice.” Captions at the bottom of the video panel allow viewers to click to find more videos or information:
• 18,000 years ago to today
• During glaciation
• After glaciation











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Quiz :

How large is the world's total water supply (salt and fresh water)?

136 million km3
1.36 trillion km3
1.36 billion km3