Ice wedge within lower part of active layer in thermokarst, Richards Island.

The active layer overlies the permafrost, and comprises earth materials that thaw from the surface and refreeze each year. It forms the interface between permafrost and the atmosphere and biosphere. The thickness of the active layer influences vegetation and soil conditions, thereby influencing hunting, gathering, forestry and agriculture. Thickness, texture and moisture content of the active layer affects foundation conditions, transportation and construction. Changes in the active layer can contribute to problems of slope instability, with subsequent impact on transportation facilities and other structures. Therefore, it is important to understand the manner in which the active layer varies locally and regionally, and to understand its response to environmental change. A program of thaw-depth monitoring in the Mackenzie Valley and Delta is utilized in order to address this situation.

Authors: M. Nixon and A. Taylor
Geological Survey of Canada