8.1: Regional Extent and Overview of the Basin and Range

The Basin and Range of the Western United States

The Basin and Range Province of California is the westernmost expression of the much larger Basin and Range Province of the southwest U.S. and western Mexico (Figure \(\PageIndex{1}\)). This region extends southward from the Columbia Plateau into central and western Mexico, and westward from the Wasatch Range of Utah and the Colorado Plateau, through eastern California. Throughout this broad continental rift zone, some 400 north-trending normal-fault bounded ranges are separated by adjacent low-lying linear basins (Figure \(\PageIndex{2}\)).

Figure \(\PageIndex{1}\): Map of the Basin and Range Province including boundaries and landmarks. The provinces is in the western U.S. and extends into northern Mexico and along the Pacific coast of Mexico. In the U.S., the province is bounded by the Sierra Nevada Mountains on the west, and extends to the east as far as the Wasatch Range of Utah and the Rio Grande Rift of New Mexico. The northern boundary of this region is the Columbia Plateau of Oregon and it extends southward into Mexico, bordering the Sierra Madre Occidental. "Basin and Range Province Boundaries and Landmarks" by Kathleen Smith is licensed under CC BY 3.0.

Figure \(\PageIndex{2}\): The Basin and Range landscape of the Basin and Range Province in Central Nevada viewed from space is a series of northwest trending mountain ranges separated by narrow basins in an arid desert region. "Basin and Range Province" by NASA is in the public domain.

Geomorphology and Climate

The Basin and Range Province of California occupies the extreme eastern limits of the state with its largest expanse found in southern California to the north of the Garlock fault and bounded on the west by the Sierra Nevada Range (Figure \(\PageIndex{1}\)). Across this region of the state, mountain ranges with elevations of more than 4,000 meters (13,000 ft.) are juxtaposed against low-elevation valleys roughly 1,000 m (3,000 ft.) above sea level. Notably, the most extreme range in relief is entirely in California. Here, the highest point in the lower 48 states, Mt. Whitney at 4,341 m (14,242 ft.), is only 85 km (53 miles) west of the Death Valley’s Badwater Basin, which is situated 86 m (282 ft.) below sea level (Figure \(\PageIndex{3}\) and Figure \(\PageIndex{4}\))!

Figure \(\PageIndex{3}\): The high peaks of the Sierra Nevada Mountains, including Mt. Whitney, the highest peak in the lower 48 US states, loom above and to the west of the rounded granite outcrops of the lower-elevation Alabama Hills near Lone Pine, CA. Mt. Whitney has an elevation of 4,341 m above sea level. Mt. Whitney by Martha House is licensed under CC BY-NC.

Figure \(\PageIndex{4}\): Satellite image of Death Valley in the Basin and Range province, eastern California. The Badwater Basin in Death Valley (marked with a red star) is at the lowest elevation in North America at 86 meters (282 feet) below sea level. Photo by Robert Simmons, based on Landsat data from the USGS Global Visualization Viewer (NASA Earth Observatory, used following NASA's image use policy). This work by Paleontological Research Institution for the Earth@Home project is licensed under CC BY-NC-SA 4.0.

Figure \(\PageIndex{5}\): A sign posted at a viewpoint in the Badwater Basin of Death Valley National Park tells the visitor that this location is 282 ft (or 855 m) below sea level. The extent of the salt flat that occupies the basin extends in the background. "Badwater Elevation Sign" by Ivan, is licensed under CC BY-SA 3.0.

This region is a desert climate due to its location in the rain shadow of the Sierra Nevada Range to the west (Figure \(\PageIndex{6}\)). At these latitudes, the dominant weather systems move from west to east. Orographic uplift occurs as eastward traveling winds are forced over the high peaks of the Sierra Nevada Range. As they rise in altitude and cool at elevation, their ability to hold water diminishes, and most of their moisture falls as rain on the windward (western) side of the range, leaving little for the region to the east (Figure \(\PageIndex{7}\)). As a result, the landscape of eastern California is dry and landforms such as alluvial fans, dune fields), and dry lake beds occur throughout the region.

Figure \(\PageIndex{6}\): The dry Owen’s Valley basin is in the rain shadow of the Sierra Nevada Range to the west. The valley sits between the high snow covered peaks of the Sierra Nevada range to the west and the Inyo Range-White Mountains to the east. Separated from the Sierras by a fault escarpment, the valley contains ephemeral lakes that fill during rainy season. "Sierra Escarpment CA" by G. Thomas is in the public domain.

Figure \(\PageIndex{7}\): As an air mass reaches the continent after flowing from an ocean (or other large body of water), the air mass is forced into the upper atmosphere by topographic barriers such as mountains in a process known as orographic lift. The side of the topographic barrier which forces the air mass upward is vegetated due to precipitation that is dropped by the rising air mass. The side of the barrier beyond the topographic high point is the rain shadow region with little to no precipitation and a resulting lack of vegetation. "Rain shadow effect caused by orographic lift" by Thebiologyprimer, is licensed under CC0.

Query \(\PageIndex{1}\)

Bedrock Geology Overview

Due to the lack of moisture in this region, there is sparse vegetation and so there is almost total exposure of bedrock geology which has contributed to the popularity of this region among geologists. Geology students from all over California and elsewhere travel to the Basin and Range to hone their geology skills.

California’s Basin and Range Province bedrock geology encompasses a broad range of geologic time and environments. The simplified geological relationships in this region can be described as North-South trending exposures of uplifted basement rocks in the footwalls of North-South trending normal faults separated by elongate, narrow basins of non-marine sedimentary rocks (Figure \(\PageIndex{8}\)). The rocks mapped in the elongate ranges include Precambrian rocks, Paleozoic sedimentary and metamorphic rocks, and Mesozoic igneous rocks. The ranges alternate with elongate basins filled with unlithified or weakly lithified units that include alluvial fans and seasonal (dry) lake beds. These basin sediments are Quaternary and Neogene non-marine units and surficial deposits which are found in the hanging-walls of the normal faults. Throughout this province, outcrops of younger (Late Cenozoic) volcanic rocks (cones, domes, flows and tuff) overlap and are cut by the normal faults.

Figure \(\PageIndex{8}\): Excerpt from the Geologic Map of California with the Basin and Range Province highlighted. “Excerpt from the Geologic Map of California” by Emily Wright, is licensed under CC-BY-NC / a derivative from the original work. Access a detailed description.

Box \(\PageIndex{1}\) Death Valley National Park

Death Valley National Park straddles the California–Nevada border, east of the Sierra Nevada. The park is one of extremes: it is not only the largest national park in the contiguous United States, it’s also the hottest, driest and lowest of all the national parks in the United States. The oldest part of the park started out as a National Monument that was established in 1933 in response to growing tourism interest in the region. UNESCO included Death Valley as the principal feature of its Mojave and Colorado Deserts Biosphere Reserve in 1984, and in 1994, the region was expanded and designated a national park.

The region has been inhabited by humans since around 10,000 years ago, and the modern indigenous community of the Timbisha Shoshone, who call themselves Nümü Tümpisattsi (″Death Valley People″; literally: ″People from the place of red ochre face paint), has been in the region for around 1000 years. European gold seekers spurred by the 1849 gold rush first moved through the area. Not only were these folks the source for the name “Death Valley”, they were also the first in a steady stream of ranchers, miners, and homesteaders who migrated to Death Valley and gradually took control of the region’s water resources and established gold, silver and borax mines.

Despite the fact that tribal members continued to live within monument boundaries throughout the early 20th century, they were seriously limited in their activities and faced ongoing challenges to their right to be there. During the 1950s National Park Service officials began efforts to evict the Shoshones from the region and prohibited them from using sacred places in the park to conduct traditional sacred ceremonies as well. It wasn’t until 1982 that the Timbisha Shoshone Tribe was recognized by the US government and a small reservation of land was established. After much tribal effort, federal politics, and mutual compromise, the Timbisha Shoshone Homeland Act of 2000 finally returned 7,500 acres (30 km²) of ancestral homelands to the Timbisha Shoshone tribe.

References

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