THE LAST GLACIATION OF BRITISH COLUMBIA, CANADA

During the last glaciation (Late Wisconsinan) British Columbia, with the exception of a few small nunatak areas, was covered by the Cordilleran Ice Sheet. This was a complex glacier mass centred in the relatively low central part of the province. Early during glaciation, glaciers grew in the mountains and pushed into the low interior where they coalesced to form an ice sheet. At its maximum the Cordilleran Ice Sheet became the main area of accumulation and the ice sheet pushed out from the central part of the province to flow over and through the flanking mountains. Because of the confinement of the mountains, considerable downwasting had to take place before significant lateral retreat could begin. This resulted in the retreating margin of the Cordilleran Ice Sheet being relatively insensitive to minor fluctuations of climate and in a very rapid disintegration of the ice sheet during later stages of retreat.

The cooling leading to Late Wisconsinan glaciation in British Columbia began about 29 ka. The maximum position of the CIS is poorly dated but was reached in the south as late as 14.5 ka. Retreat was rapid and by 10 ka, ice cover in British Columbia was approximately as extensive as at present. Illustrations show the general paleogeography of the area at various times during retreat of the Cordilleran Ice Sheet.