The Canadian Shield was formed by the former mountain range that was eroded due to weathering. Weather played an extremely important role in creating the Canadian Shield because the wind and rain wore down the mountains. The process of forming the Canadian Shield didn’t happen overnight. Studies suggest that it formed over 3 billion years through the process of glaciation, erosion and plate tectonics (which forms large landmasses when it collides).
The largest of these mountain ranges is the Grenville Orogeny which created the Grenville Mountain Range stretching from Quebec through Ontario and down to East Texas. Temperature differs along different sides of the Canadian Shield – very cold in the northern part of the Shield and cold and warm in the southern part of the Shield.