In the southern foothills the contact of two major glaciations is located in the region where the Laurentide, or continental ice, from the north and east, met the streams of ice pouring down the valleys from the Cordilleran glaciers to the west. Generally where both are found, and can be distinguished, the Cordilleran drift underlies that of the Laurentide. The Cordilleran drift contains sedimentary stones whereas the Laurentide contains stones of igneous origin. The Laurentide ice was thin in this region and lacked the erosive power of the thick ice to the east and hence the existing topography controlled the movements of the ice. The Alpine glaciers, however, moved rapidly and had strong erosive power. There is evidence of two, and possibly three, major Laurentide glaciations. The direction of movement of the Cordilleran was downhill and is usually obvious. Its eastern movement is confirmed by drumlins, moraines and striae on the harder rocks. The best method of determining the Laurentide movement is through tracing erratics to their source rocks. The most western advance of Laurentide ice into the foothills is to be found, so far, some 20 miles north of the U. S. border at an elevation of 5, 280 feet. One of the important aspects of the glaciation was the diversion of drainage and formation of glacial lakes.

Abstract by R. R. Williams, P & N G Conservation Board.

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