“I forgot how big, Big Rock really is!” Sue and I stroll up to the rather oversized boulder in the middle of the flat farm field, just south of Calgary, Alberta, near the town of Okotoks. Weighing in at 16,500 metric tonnes (18,000 tons), you might say my ‘oversized boulder’ description of Big Rock Okotoks is a bit of an understatement.
The official name for Big Rock is “Okotoks Erratic” with Okotok being the First Nations Blackfoot term for this big rock. However, so as not to confuse the boulder with the nearby town and namesake Okotoks, we’ll use Big Rock as its name.
This of course is not meant to confuse Big Rock with the well established local craft brewery, Big Rock Brewery (but I digress).
“I wonder how it got here?” I stare at the monolith sitting in the middle of nowhere. The Canadian Rocky Mountains are a mere 50 km (30 miles) away, but that still seems like an extraordinary distance for this beast of a boulder to travel.
If you remember my reaction to the Victoria Falls earlier this year, I just have to know what the heck happened here!
How did Big Rock Okotoks come to be?
Well, it turns out that Big Rock traveled to its place of rest during the last ice age, some 12,000 to 17,000 years ago. It didn’t travel a measly 50 km (30 miles), but closer to 500 km (300 miles) from farther northwest in the Rocky Mountains.
It was the largest rock of many chunks that made up the “Foothills Erratic Train” which stretches along the Foothills of the Rockies in Alberta and into northern Montana in the United States.
So here’s how it happened. (Note: If you don’t give a rat’s butt about how the big rock actually arrived in Okotoks, then skip to the video below. There’s footage from our new drone!)
Roughly 15,000 years ago, give or take a few of thousand years, glacial scouring of the Tonquin Valley near Jasper Alberta ultimately caused a massive rock slide, sending tons of rock onto the glacier below.
This glacier, being part of the Cordilleran Ice Sheet , transported Big Rock out of the mountains in an eastward direction. Once out of the mountains the glacier collided with the much more significant Laurentide Ice Sheet. Big Rock was diverted southward along the foothills of the Rocky Mountains.
It continued along this path until the ice age ran out of proverbial steam, and settled onto the flat field near Okotoks where it resides today. This journey took only approximately 3,000 years.
Now I really have an idea of what the term ‘glacial speed’ means.
Check out our video below which gives a rather crude animation of the Big Rock travels. As well see some images and drone footage of the super-stone.
Are there any interesting natural wonders in your neck of the woods?