At the easternmost tip of Canada’s Banff national park lies Lake Minnewanka. The lake fills a zigzagging valley just north-east of the city of Banff. Fed by the Cascade river, Minnewanka owes its existence to a succession of dams, the first built in 1895, the second in 1912, and the third in 1941. The second dam raised the lake’s level by 3.5 metres, and the third dam by 30m. The area has been shaped by a combination of rivers and glaciers. Beginning 25,000 years ago, the Bow valley glacier ground through the region before being overtaken by a continental glacier. Besides the Bow valley, evidence of glaciation also appears in this image south of the lake, in the amphitheatre-shaped cirque
Photograph: ALI/EO-1/NASA
The Guardian
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