OverviewTurtle Mountain is an easy scramble. I felt compelled to add it due to it's uniqueness and geological educational value.
Turtle Mountain is part of the Blairmore Range located in the Crowsnest Pass region of southern Alberta, north of Waterton National Park. It is best known as the site of the tragic Frank Slide of 1903 that claimed most of an entire town killing over 70 people. The mountain was said to resemble a turtle, thus officially named in 1880, however, the likeness was lessened by the 1903 rockslide. The Indians would not camp beside it knowing that it moved on a regular basis.
Turtle Mountain is a faulted anticline, the beds of rock rising on its west side, curving over the top, and dipping steeply on the east side. The bedding surfaces between the layers of limestone are zones of weakness as are fractures or joints which cut through the rock at right angles to the bedding surfaces. Water constantly finds its way into the weaker zones (which is evident between the two summits), freezes and expands, and makes the cracks larger. In the case of Turtle Mountain, the two zones of weakness (the joint surfaces in the upper part and the bedding surfaces in the lower part) lined up. As well, these steeply dipping rocks were poorly supported by weaker rock below, some of which was being removed by active mining. It took millions of years to set the stage but the slide was over in seconds.
On April 29, 1903, part of the eastern summit of Turtle Mountain broke away and slid down the mountain side, burying the south side of the town of Frank to depths of thirty meters and then rushed up the opposite side of the valley to a height of 120 meters.
Although this dramatic event took place almost a century ago the scar and debris look remarkably fresh and provide dramatic evidence of how the erosion of our mountains, generally a process which is the summation of vast numbers of minor events, can be hastened by single massive events. In this case a piece of limestone 425 meters high, 1000 meters wide, and 150 meters thick with a weight estimated to be eighty-million tons, broke off the mountain. The debris covers about three square kilometers to a depth averaging fourteen meters.
The "Air Cushion Theory" explains why the debris traveled much farther and covered a wider area than would be expected. The theory suggests that the rock rode out over the valley on a layer of trapped, compressed air. This appears evident from the summit.
In 1904, Turtle Mountain was first ascended by Edward Whymper. This straightforward scramble takes you up to and across the ridge between the two summits where the massive rockslide began, and is far more interesting than the limited view from the nearby visitor center. Furthermore, the ascent lets you gaze straight down the face to the devastation below.