 As the North American Plate drifted west and the Intermontane Plate continued to drift east to the ancient continental margin of Western Canada, the Slide Mountain Ocean began to close by ongoing subduction under the Slide Mountain Ocean.This subduction zone eventually jammed and shut down completely about 180 million years ago, ending the arc volcanism on the ancient continental margin of Western Canada and the Intermontane Islands collided, forming a long chain of deformed volcanic and sedimentary rock called the Intermontane Belt, which consists of deeply cut valleys, high plateaus, and rolling uplands.This collision also crushed and folded sedimentary and igneous rocks, creating a mountain range called the Kootenay Fold Belt which existed in far eastern British Columbia.