Canada is the second largest country in the World covering 10 million km2, much of it being north of the Arctic Circle. The central plains and lakes, which overlie the Canadian Shield, are flanked respectively by the Rocky Mountains to the west, the older Appalachian chain to the east, and an archipelago of Arctic Islands to the north. The country has an extensive common border with the United States, much drawn along the somewhat artificial line of the 49o Latitude. It is flanked to the northeast by the autonomous Danish territory of Greenland and to the north by the Arctic Ocean. It is a very sparsely populated country supporting no more than about 35 million.