How The Cordillera Was Formed

There are 3 sections of the Western Cordillera:

Eastern Mountains:
     This division of the Western Cordillera is made up of two mountain ranges, the Rocky and the Columbia Mountains, separated by a deep valley. The Rocky Mountains, Canada's youngest mountains, were created by  folding and faulting and are almost entirely made up of sedimentary rock.
     The valley separating the mountains is known as the Rocky Mountain Trench. It was created by erosion along a zone of faults.
     The Columbia Mountains are similar to the Rocky Mountains and were made by folding and faulting. They are not as tall because they are older than the Rockies. They are made up of sedimentary rock and some metamorphic rock in layers below the surface.

Interior Plateaus
     The Interior Plateaus are in the center of the Cordillera and were made by volcanic activity. The area is composed of igneous and metamorphic rock and contains valuable metals such as copper, zinc and even gold.
Coast Mountains
     The Coast Mountains are split into two ranges divided by a deep trough, just like the Eastern Mountains. It is divided into The Coast Mountain Range, which is on the mainland, and the Island Mountain Range, which is located on the offshore islands. The Pacific Ocean runs through the trough that divides the two Mountain Ranges. The Coast Mountains were formed by convergent plate movement. The Pacific Plate went under the North American Plate and the pressure caused magma to rise into the Earth's crust and when it cooled it formed the Coast mountains. The movement of the two plates up against one another also uplifted a massive amount of rock. The Coast mountains are a block of igneous and metamorphic rock.