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Okotoks Erratic

When the ice started to melt and the glacier began its retreat, the rocks, known as "erratics", were left behind in a ribbon extending from Jasper along the western prairie margin south to northern Montana, roughly the contact zone between the continental and mountain ice sheets. Of this group, known collectively as the Foothills Erratics Train, the 16-tonne (17.6 ton) piece at Okotoks, dropped at its final resting place about 12,000 years ago, is by far the largest; indeed, it is considered North America’s largest glacial erratic.