Canada may be divided into seven physiographic regions. The Canadian Shield is the largest and oldest of these regions. The other six physiographic regions are younger and form two concentric rings around the Canadian Shield. The outer, older ring contains the Western Cordillera, Canadian Arctic and Appalachian Region. The second, younger ring contains the Interior Plains, Hudson Bay Lowlands and the St. Lawrence Lowlands. These regions may be further sub-divided based on their structure, relief and the presence or absence of permafrost and forest cover (see Natural Regions).
Areas quoted for these regions are the land areas and do not include adjacent continental shelves or bodies of ocean water within Canada's territorial limits. Readers should also note that the abbreviation “masl” stands for “metres above sea level.”