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Foothills Erratics Train
In southern Alberta, along the eastern side of the Rocky Mountains, thousands of large boulders (erratics) form a train over 600 kilometres long. These rocks contain clues that have helped scientists to understand the movements of the ice sheets that covered Canada during the ice age.
When geologists examined the rocks, they discovered that they were all made of the same kind of rock, and they traced the source of that rock to an area around Mount Edith Cavell in Jasper Park. Thousands of years ago, these large stones fell onto the surface of the Cordilleran ice sheet during a landslide, and then were slowly carried by the ice sheet outward onto the Plains. When the ice melted, a long train of boulders was left behind.
The pathway of the erratics train reveals the direction in which the ice sheet travelled. The rocks take a sharp right-angle turn out on the Plains, changing from an easterly to a southerly direction. Scientists believe that the western Cordilleran ice sheet “bumped into” the eastern Laurentide ice sheet, and got deflected southward. This shows that the two ice sheets were joined together, and no “ice free corridor” could have existed between them until later, when the glaciers started to melt.
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