The behaviour of the ground in the cold regions of the world is characterized by freezing and thawing. The porous and particulate nature of soils presents conditions for phase change which lead to their unique properties and behaviour in cold climates. Accordingly, the periodic and unstable nature of atmospheric climate and of surface microclimate produces characteristic disturbances in the near-surface layers of the ground in the cold regions. These include the consequences of melting such as subsidence (thermokarst topography) and instability of slopes (landslides, mud-flows), as well as the thermodynamic and mechanical effects of freezing, especially frost heave. Frozen soils show temperature-dependent creep (some forms of solifluction and deformation of foundations) and continuing heave (expansion of ground over long periods of time). These effects have important geotechnical implications' for the design of highways, airports, buildings and, notably, pipelines. The complexity of the design problems for major structures, especially pipelines, has not been widely understood. If there is global warming due to anthropogenic emissions of gases this will influence the direction and intensity of the ground disturbances, the nature of which has been recognized over the last three or four decades. However the effects of such warming due to atmospheric climate change will only become apparent over many decades. In the short term they will be masked by other ground temperature changes due to microclimatic effects and to inter-annual variability of climate and weather. Over a period of a century or more, if warming trends continue, there will be important modifications of terrain and physiography.
