Have you heard of “The Big Rock” in Okotoks? It’s an enormous glacial rock or “erratic,” meaning it was transported far away from its origin by glacial ice. The largest known rock in the Foothills Erratics Train is the Okotoks Erratic which was a group of rock carried along the mountain front by ice and let down as the glacier melted.
This took place over 10,000 years ago and the erratics now lie in a narrow area extending all the way to northern Montana from Jasper National Park. Even though the rock has broken into pieces, it’s still a large landmark on the flat prairie weighing 16,500 tonnes and measure 9 metres high. Here is a look at the “big rock” in Okotoks.
Visiting the “Big Rock”
It’s located off highway #7 which is 10 kilometres southwest of Okotoks. You can visit but you can’t climb the rock because the quartzite is slippery with pieces breaking off in climbers’ hands. It will look tempting to climb but it’s not meant to be climbed because you could damage the aboriginal pictographs found on the rock. Stay on the ground and enjoy the colours, textures and feel of the rock. The City works to preserve this Provincial Historical Resource.
About the “Big Rock”
The “Big Rock” has hardened layers of sand, smell pebbles and silt that you can see up close. The layers of sediment deposited around 520 million years ago are a piece of the Gog Formation. Sediment was buried layer on layer as time passed and then heat and pressure generated by the weight over the sediments compacted and cemented sand grains into a hard rock called quartzite.
Big Rock was originally a part of a mount that is now Jasper National Park. Since the Rocky’s are made of limestone, quartzite is less commonly found there and was only discovered when a large rockslide crashed debris onto a glacier occupying present day Athabasca River valley.
The debris included Big Rock and was carried on the surface of the glacier before it slowly moved to the mountain front, collided with an ice mass before deflecting southeast and depositing erratics after the ice melted.
Check out the Big Rock which is split down the middle appearing to have faces on it and is revered by the Blackfoot people of Okotok.