I drove through the Crowsnest Pass, connecting southern Alberta with southeastern BC, several dozen times in the past decade while traveling between Spokane and Calgary. It's a very scenic stretch of road through the heart of Canada's amazing Rocky Mountains.
(View of fallen rock from the highway)
The first time I made the journey I noticed that the road passed through a stretch of broken rocks. My first thought was that these might be mine tailings, but the rocks were clearly much too large for that. So it had to be the remnants of a rockslide, which I was to learn is named the "Frank Slide".
The following photo was last Saturday's One Clue Mystery photo. It was recognized by George G and Jonathan L -- congratulations to both.
The best place to learn about this rockslide is at the Frank Slide Interpretive Centre, which provides a great view of the rockslide site as well as an interesting background of the history and the many people who lost their lives here. The Frank Slide remains Canada's deadliest rockslide.
(Frank Slide Interpretative Center)
The Frank Slide occurred at 4:10 in the morning on April 29, 1903. A large section of Turtle Mountain collapsed into the coal-mining town of Frank. The slide was caused because of the unstable geologic structure of the mountain, with folded layers of sedimentary rock arranged almost vertically. Erosion and the actions of ice and water caused deep cracks and further instability in the mountain, until it all just came down on that fateful morning.
(Photo of the town of Frank, taken before the landslide)
The noise of the slide was incredible -- it could be heard 120 miles away. The slide lasted about 100 seconds and was likened to steam escaping under high pressure. Scientists estimate that rocks were moving at about 120 kilometres/hour (70 mph).
(Photo of the town of Frank, after the massive rockslide)
It's estimated that the limestone which fell from the top of Turtle Mountain during the Frank Slide was approximately 1 kilometer wide, almost half a kilometer high and 150 meter thick. This calculates to 110 million metric tons. The Crowsnest Valley at the site was covered to a depth of 14 meters (46 feet), with some spots as deep as 45 meters (150 feet), spread over 3 square kilometers.
(Views of the Frank Slide taken from the Interpretative Center, showing the magnitude of the rockfall)Of the 600 people living in Frank at the time of the rockslide, more than 90 were killed (leaving more than 500 alive). The bodies of most victims were never recovered because of how deeply they were buried under the fallen rock.
(Signage from the Interpretive Center).
After the Frank Slide people from the townsite of Frank began to move away, fearing another similar disaster. Government officials were worried that Turtle Mountain was still unstable, so the remaining buildings in Frank were relocated or torn down.
(The Interperative Center shows the limits of the rock slide -- the so called "Splash Zone")
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