Major Features
This cordillera extends from the U.S. state of Alaska to the southern border of Mexico. The North American Cordillera includes some of the highest peaks on the continent. Its mountain ranges generally run north to south along three main belts: the Pacific Coast Ranges in the west, the central Nevadan belt in the middle (including the Sierra Nevada), and the Laramide belt in the east (including the Rocky Mountains).
These three orogenic belts arose due to the engagement of tectonic plates which deformed the Earth's lithosphere (crust and uppermost mantle). For example, the Laramide orogeny changed the topography of the central Rocky Mountains and adjoining Laramide regions (from central Montana to central New Mexico) during the Late Cretaceous 80 million years ago. Prior to this time the Rocky Mountain region was occupied by a broad basin. Further topographical evolution occurred during the Eocene (50-55 million years ago) and Oligocene (34-23 million years ago), but since that time the deformation of the region has been relatively stable. Generally speaking, it will be convenient here to consider these three belts going west to east, and north to south.
In Alaska, south of the Interior Plains area, is the Rocky Mountain System, then the Intermontane Basins and Ranges, and in the southern part of the state are the Pacific Mountains and Valleys. In the Alaska panhandle, the mainland mountain ranges and offshore islands (the Alexander Archipelago) are extensions of respective ranges further south.
In Canada, the North American Cordillera is usually divided into three physiographic regions: the western system, the interior system, and the eastern system. The western system includes the Coast Mountains, the interior system includes the Columbia Mountains, and the eastern system includes the Canadian Rockies.
At its midsection between San Francisco, California and Denver, Colorado, the North American Cordillera is about 1,000 miles (1,600 km) wide, and its physiographic provinces at this midpoint are as follows, going from west to east: the Pacific Coast Ranges, the Central Valley, the Sierra Nevada, the Basin and Range province (forming many narrow ranges and valleys), the Colorado Plateau, and the Rocky Mountains. In the United States, another major feature of the Cordillera is the Columbia Plateau, located north of California between the Cascade Range — which is a northern extension of the Sierra Nevada — and the Rocky Mountains.
In Mexico, the Sierra Madre Occidental, and the Sierra Madre Oriental further east, surround the Mexican Plateau. To the west of the Sierra Madre Occidental, the Peninsular Ranges border the Pacific Ocean, and the Sierra Madre del Sur is the southern extension of the Peninsular Ranges. Sierra Madre means "Mother Range" in Spanish.
The Nevadan belt runs up and down the middle of the North American Cordillera. Therefore, the intermontane areas of the cordillera can be divided up into the areas east of the Nevadan belt, and those west of the Nevadan belt.
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