The Cordillera of western North America occupies the central 5000 km of the circum-Pacific orogenic belt, which extends for 25,000 km along a great-circle path from Taiwan to the Antarctic Peninsula. The North American Cordillera is anomalous because dextral transform faults along its western flank have supplanted subduction zones, the hallmark of circum-Pacific tectonism, along much of the Cordilleran continental margin since mid-Cenozoic time. The linear continuity of the Cordilleran orogen terminates on the north in the Arctic region and on the south in the Mesoamerican region at sinistral transform faults of Mesozoic and Cenozoic age, respectively.

The Cordilleran margin...