East of the Rocky Mountain front in Alberta lies a train of metaquartzite boulders. Randall has followed it 500 miles up the mountain front and into the Athabasca River valley, toward the Continental Divide near Jasper. The boulders trace back to Mount Edith Cavell.
The puzzle is that Mount Edith Cavell sits on the western side of the Continental Divide, while the boulder train lies on the eastern side. So how did huge boulders get across? His answer: they were carried aboard icebergs.