Intensive exploration for petroleum deposits is taking place in the sedimentary basins of northern Canada which are in the physiographic regions comprising the Interior Plains on the mainland, the Arctic Archipelago, the Arctic Lowlands and Plateau, and the Innuitian region. The distribution of permafrost ranges from scattered islands less than 50 ft thick in the southern fringe of the discontinuous zone in northern Alberta and British Columbia to continuous--perhaps 300-1,000 ft thick--in the Mackenzie Delta. The sedimentary basins in the Arctic Islands lie entirely within the continuous zone with permafrost ranging in thickness from about 1,000 to 2,000 ft or more. Ground ice, a commonly occurring and vital component of permafrost is found in a variety of earth material comprising various types of landforms, and also in bedrock. Ice forms include segregated ice, pore fillings, intrusive or injected ice, vein or wedge ice, and buried ice. Although the existence of ground ice may be inferred in places from certain features of the terrain, e.g., pingoes and ice wedge polygons, the distribution and type of ice are not readily determined in many cases.

The effect that construction and other activities have on the ground thermal regime in permafrost areas is a prime consideration. Most engineering problems are caused by thawing of perennially frozen ground containing large quantities of ice. Disturbance of the surface cover and heat loss from structures causing degradation of permafrost in areas underlain by ice-rich materials will result in large-scale ground subsidence and drastic differential settlements. It is most important, therefore, that site investigations be carried out to provide information on the distribution of permafrost, the conditions under which it exists, and its properties and characteristics so that unsuitable or potentially troublesome areas or routes can be delineated.

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