Primarily the sun, but it energy is also released as gravity pulls the mass of the Earth inward (analogous to a ball gaining energy as it falls).
Volcanoes occur at underwater subduction zones. In fact, volcanoes form at most if not all types of subduction zones. Subduction zones are regions where tectonic plates collide and one plate bends and slides underneath the other plate. This bent plate reaches the mantle of the Earth, putting more pressure on the hot materials inside it.
Geographically the North American continent is divided into few parts in east-west direction, while the political divide of the continent is in north-south direction and it's not following the natural borders but cuts across them. The USA and Canada landforms are linked through the Appalachian Mountain Range along the east coast, the Great Plains that start from the Caribbean coast in the south and go through the heart of the continent north to the Arctic waters, and in the west it is the Rocky Mountain Range and the Cascades that are connecting the two countries geographically.
