The Geodynamics Program of the Geological Survey of Canada delivers information on contemporary movements of the Earth's crust for earthquake hazard and global change studies. On the densely populated west coast of Canada, for example, measurable movements are occurring as plate tectonic stress builds up along the western edge of the North American plate. During this strain accumulation stage, prior to an earthquake, surface deformation is expected and can be measured. The slow movements we measure can be related through computer models to changes in stress taking place in the crust (the upper 35 km of the Earth) where most destructive earthquakes are expected to occur. The observed pattern and magnitude of crustal movements assists in determining the potential for a large magnitude (greater than magnitude 8) subduction earthquake as well as the potential for intermediate magnitude (magnitude 6-8) earthquakes along the continental margin.

The principal tools used by the Geological Survey of Canada to measure crustal movements are the Western Canada Deformation Array (WCDA), a network of permanent Global Positioning System (GPS) tracking stations, and a transportable absolute gravimeter. Other techniques used in co-operation with other agencies are GPS surveys, precise spirit levelling, Very Long Baseline Interferometry (VLBI) and permanent tide gauges. These independent measurement techniques corroborate and complement each other in establishing crustal deformation patterns and crustal strain rates.

The Global Change component of the Geodynamics Program focuses on the effects of postglacial rebound. The weight of the continental glaciers of the last great ice age (which peaked about 20,000 years ago) depressed the surface of the Earth. As the great ice sheets retreated and shrank, the Earth's crust began to rebound to its former level. Peak regions of rebound under the former ice sheets are located in Canada and Fennoscandia. Antarctica, which is still glaciated, is also experiencing substantial rebound because the Antarctic ice sheet has shrunk. Postglacial rebound has affected, and continues to affect, the drainage patterns of lakes and rivers through the continuing tilting of the Earth's surface. Sea level is affected by the melting of glaciers in two important ways:

1. meltwater from glaciers changes global sea level by changing the volume of water in the oceans

2. vertical movement of the land associated with the Earth's response to unloading produces a local apparent change in sea level

The Geodynamics Program utilizes GPS and absolute gravity observations to determine present day tilting, and integrates these observations with geological observations through computer models that simulate the retreat of the ice sheets and the Earth's ongoing crustal response.