Jurassic

The Jurassic (210-140 million years ago) was the major period of mountain-building in the Columbia Basin (Monger, in Ludvigsen, 1996). The piece of the Earth's crust known as the North American Plate moved northwest over the ancestral Pacific basin, sweeping up terranes (pieces of other continents) on its leading edge. The crust was thickened by folding and thrust-faulting of terranes over one another and over the old Continental edge. The folding brought up ancient (before evolution of life) layers from deep in the Earth’s crust, and intense pressure created metamorphic rock with granitic intrusions typical of the Selkirk, Monashee and Purcell Mountains, while the marine sediments of the old continental margin were thrust up to form the Rockies. This seems terribly cataclysmic, but these pieces of the Earth's crust moved at a pace of only millimetres per year, much as they do now. For example, the distance between Revelstoke and the Rocky Mountains was scrunched from 600 to 300 kilometres - a pace of just 4 millimetres per year averaged out over 70 million years! Even glaciers move faster than that.