Semi-Subterranean houses with an entrance through the roof are a well known feature of the interior of British Columbia, having been described for the Thompson, the Chilcotin, the Shuswap and others of the upper Fraser River valley. They have, in fact, an even wider distribution east of the Coast and Cascade Ranges, extending south over the Plateau and into northern California. Although this type of dwelling existed among the Aleuts, it appears that the coastal people to the south of them, even in Alaska, were either unfamiliar with the pattern or rejected it in favor of others. Sporadically, along the Pacific Coast all the way from California to Bering Sea, house floors were excavated to varying depths, sometimes even to two levels; but, everywhere, the houses characteristically lack the roof entrance and, except for sweathouses in the south and Bering Sea Eskimo dwellings in the north, even the idea of an earth covering is absent. In view of this fundamental divergence, it is interesting that subterranean structures do appear in several places on the coast of British Columbia.
A huge flood in the Fraser River valley, British Columbia, near the Pleistocene Termination