1 Specifically, the structural subdivision of the western USA between the Colorado Plateau to the east and the Sierra Nevada to the west. It is dominated by a series of block-faulted ranges and troughs which dissect it, rising above bajadas and alluvial plains which mask down-faulted units. Frequently the ranges are tilted blocks approximately 30–40 km across. Movement occurred initially in Miocene times, and then during the late Pliocene to Recent.
2 Generally, applied to landscapes having a series of tilted fault blocks that form long, asymmetric ranges separated by broad basins.