By Erin Wayman
The building of western North America wasn’t a simple construction job. Multiple sections of seafloor slid beneath the continent and each other like conveyor belts, researchers suggest, bringing islands in from different directions and pasting them to the western edge of North America in a jumble of rugged terrain.
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“It’s a major change in how we view the tectonic history of North America,” says geophysicist Don Forsyth of Brown University in Providence, R.I., who wasn’t involved in the work. “It’s a mini-revolution.”
North America west of the Rocky Mountains is a patchwork of different islands and other fragments of crust that the continent accumulated over the last 200 million years. The accumulation began when North America broke free from Pangaea and started drifting west.