big rock okotoks

The Big Rock in Okotoks is a geological wonder in Canada formed thousands of years ago

The Okotoks or Big Rock erratic is the largest known glacial erratic in the world, weighing in at over 18,000 tons.

This massive rock formation is located eight kilometres from the town of Okotoks in Alberta, from which it gets its name and was formed by dislodged rocks that traveled on top of a glacier thousands of years ago.

It was originally part of a mountain formation in what is now Jasper National Park. About 30,000 years ago, at the time of the last ice age, a large rockslide crashed debris onto the surface of a glacier in the present day Athabasca River Valley.

The glacier broke away and travelled through the Rocky Mountains before eventually melting and dropping those rocks throughout the otherwise flat and sparse landscape of the surrounding prairies. 

This impressive 30-foot high and 60-foot long boulder is the crown jewel of the 930 kilometre stretch of the Foothills Erratics Train, a long linear scatter of thousands of distinctive quartzite and pebbly quartzite that extends along the Rocky Mountains of Alberta. 

The boulders and smaller gravel, which comprises the Foothills, consist of Lower Cambrian shallow marine quartzite and conglomeratic quartzite, which occurs only within the western regions of the Canadian Rockies. 

This rock also holds a lot of significance for the First Nations and was declared a Provincial Historic Site in 1978 to protect its geological and cultural importance.

Long before European settlement, it was used as a landmark for finding a crossing over the Sheep River, where Okotoks stands today. Its stone also contains native pictographs. 

Big Rock is definitely worth a visit, and it's incredibly easy to get to. The rock is located right along the side of Highway 7, public parking is available at the turn-off, and there's no long hike necessary. 

Lead photo by

krystlesimmonds


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