In the latest Early Jurassic, about 180 million years ago, a major change of plate motions led to the growth of mountains on the site of the old submerged continental margin and ocean floor along western North America. This change may be related to the opening of the Atlantic Ocean which accompanied the break-up of the supercontinent Pangea. At about the same time as the North Atlantic opened, the North American plate started to plough northwestward towards and over the ancestral Pacific basin. In so doing it picked-up and plastered-on the terranes to the leading edge of the old continent. This process, combined with squeezing of the hot, weak crust along the edge of the plate above the subduction zone, thickened the crust and built the Cordilleran mountains.

Events leading to the present Cordillera were localized in the late Early Jurassic (about 180-170 million years ago) in the region centred on the present Omineca Belt, when Slide Mountain and Quesnellia terranes were thrust eastwards over rocks that formed along the old continental margin. By 170 million years ago, Cache Creek terrane was thrust westwards over Stikinia in northern British Columbia. The rocks below the thrust faults were buried 10 to 30 km, metamorphosed, and in places partly melted to form granitic rock. It is these deeply buried rocks, later uplifted, eroded, and exposed at the surface, that give the Omineca Belt its metamorphic character. As the rocks in the Omineca Belt were uplifted and eroded, they shed vast quantities of sand, gravel and mud westward onto Stikinia and ultimately on to the ocean floor, and eastward onto the older sediments of the Foreland Belt. The initial marine deposition in the basins flanking the Omineca Belt was followed by non-marine sedimentation as more and more of the region was uplifted above sea-level. The deposits of limestone and shale along the old continental margin, together with the overlying sandstones and shale eroded from the uprising Omineca Belt to the west, were then thrust eastwards onto the margin about 100 million years ago.

The last big terrane, Wrangellia, was accreted to the western edge of the welter of previously accreted terranes in the mid-Cretaceous, about 100 million years ago. Wrangellia's eastern boundary is within the southwestern Coast Belt, but is masked by the widespread Middle Jurassic and Early Cretaceous granitic rocks. The jaws of the tectonic vice are Wrangellia and the southwestern Coast Belt to the west, and the Cretaceous edge of North America to the east, which was located near the present Coast-Intermontane belt boundary. The crunch zone between is the southeastern Coast Belt, between Harrison Lake and Lillooet. As the vice was closed between Wrangellia and terranes to the east, the rocks in the vice were squeezed downwards and upwards, metamorphosed and uplifted. Sand and gravel eroded from the uplifted Coast Belt was shed westwards into the Late Cretaceous and early Tertiary basins on Wrangellia in the Insular Belt, and onto the Pacific Ocean floor. By the Late Cretaceous, the main characteristics of all five belts were well established.