Basin and Range Province

The Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. The region covers much of the western United States, extends into northwestern Mexico and is mostly desert, with numerous ecoregions. The physiography of the province is the result of tectonic extension that began around 17 Ma (million years ago) in Early Miocene time.

The numerous ranges within the Province in the United States are collectively referred to as the Great Basin Ranges, although many are not actually in the Great Basin. Major ranges include the Snake Range, the Panamint Range, the White Mountains, the Sandia Mountains, and the Tetons.

Depending on the various geographical definitions of the Province, the highest point of the Province is either Mount Whitney or Pico de Orizaba, both of which are located at the boundary of the Province and belong to other geologic regions as well. The highest point fully within the Province is White Mountain Peak in California, while the lowest point is the Badwater Basin in Death Valley at −279 feet (−85 m).

Basin and range topography

Basin and range topography results from crustal extension (extensional tectonics). As the crust stretches, faults develop to accommodate the extension.

For example, in the western United States, this topography is built by a number of normal faults that meet at a basal detachment fault. The basins are down-fallen blocks of crust and the ranges are relatively uplifted blocks, many of which tilt slightly in one direction at their tops due to the motion of their bottoms along the main detachment fault.

The normal arrangement in the basin and range system is that each valley (i.e., basin) is bounded on at least one side by one or more normal faults that are oriented along, or sub-parallel to, the range front.

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