The Okotoks Erratic, or Big Rock, is located in an otherwise flat landscape in the Canadian Prairies in Alberta, just outside the City of Okotoks,  54 kilometres south of Calgary. It is the largest Glacial Erratic within the Foothills Erratic Train, consisting of quartzite and quartzitic conglomerate that originated from a landslide in the Athabasca River Valley and was then carried on top of a glacier to where it lies today.

Big Rock is visible from a long distance and the people of the Blackfoot First Nation used this erratic as a landmark for finding a safe way across the Sheep River.  The rocks contain pictographs and were deemed a medicine rock by the Indigenous People.  In the 1970’s, the province declared Big Rock a Provincial Historic Site to preserve and protect its cultural and geologic significance.

Allan Derbyshire, Canada’s first ACMG rock guide and a retired professor from Mount Royal College, was instrumental in helping to maintain access to climbing even after the Historic Site status was gained.

Today, it is still permitted to boulder on Big Rock, though it is very important to never climb on any surfaces that have pictographs.  As well, bolted is prohibited and chalk use is asked to be limited.  It is important to have respect for a site considered important to the Indigenous people.

One interesting feature of Big Rock is the large split down the middle. A Blackfoot story describes how this may have happened:

One hot summer day, Napi, the supernatural trickster of the Blackfoot peoples, rested on the rock because the day was warm and he was tired. He spread his robe on the rock, telling the rock to keep the robe in return for letting Napi rest there. Suddenly, the weather changed and Napi became cold as the wind whistled and the rain fell. Napi asked the rock to return his robe, but the rock refused. Napi got mad and just took the clothing. As he strolled away, he heard a loud noise and turning, he saw the rock was rolling after him. Napi ran for his life. The deer, the bison and the pronghorn were Napi’s friends, and they tried to stop the rock by running in front of it. The rock rolled over them. Napi’s last chance was to call on the bats for help. Fortunately, they did better than their hoofed neighbours, and by diving at the rock and colliding with it, one of them finally hit the rock just right and it broke into two pieces.

Not only does this story explain why the rock is in two pieces, but also why bats have squashed-looking faces. The tale provides helpful caution against taking back what you have given away. (Wikipedia)