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Alberta Online Encyclopedia

Big Rock: Okotoks Erratic

This enormous quartzite block is very different from the soft local sandstone-it comes from the Rocky Mountains. It was carried here on the surface of a glacier between 18 and 10 thousand years ago. Rocks like this one are called “glacial erratics.” Rockslides in the Athabasca River valley deposited quartzite debris on a glacier, which flowed slowly to the plains. When the ice melted, a string of erratics extended from Jasper to northern Montana. The Big Rock is the largest, weighing 16,500 tonnes and measuring about 41 x 18 x 9 metres. It is a Provincial Historic Resource.

Highway 7 west of Oko toks. (403) 562-8635. Within Alberta, dial 310-0000 to be connected toll free.


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