Misplaced Pages

#596403

36-831: The Salton Trough is classified as a distinct section of the Basin and Range Province within the Intermontane Plateaus division. The northwestern end of the trough starts at the San Gorgonio Pass in Riverside County and extends 115 miles (185 km) southeast to the Gulf of California . Major geographical features located in the trough include the Coachella Valley , the Salton Sea , and

72-476: A subduction zone is transferred to the overriding plate as subduction proceeds. Fluids along fault zones then transfer heat vertically through the crust. This model has led to increasing interest in geothermal systems in the Basin and Range, and requires consideration of the continued influence of the fully subducted Farallon plate in the extension responsible for the Basin and Range Province. In some localities in

108-472: A temporary lake known as Lake Manly . Newly formed lakes do not last long though, because the 1.9 in (48 mm) of average rainfall is overwhelmed by a 150 in (3,800 mm) annual evaporation rate and usually lakes are only a couple inches deep. This is the greatest evaporation potential in the United States, meaning that a 12 ft (3.8 m) lake could dry up in a single year. When

144-530: A thin white crust over mud), and so the sign marking the low point is at the pool instead. The basin was considered the lowest elevation in the Western Hemisphere until the discovery of Laguna del Carbón in Argentina at −344 ft (−105 m). At Badwater Basin, significant rainstorms flood the valley bottom periodically, covering the salt pan with a thin sheet of standing water, forming

180-552: Is a complex and controversial issue among the geoscience community. The most accepted hypothesis suggests that crustal shearing associated with the San Andreas Fault caused spontaneous extensional faulting similar to that seen in the Great Basin. However, plate movement alone does not account for the high elevation of the Basin and Range region. The western United States is a region of high heat flow which lowers

216-549: Is arid, with numerous ecoregions . Most North American deserts are located within it. The Basin and Range Province should not be confused with the Great Basin , a region defined by its unique hydrological characteristics (internal drainage) that overlaps much of the greater Basin and Range physiographic region. Nor should it be confused with the Basin and Range National Monument , located in Southern Nevada, which

252-402: Is generally accepted that basin and range topography is the result of extension and thinning of the lithosphere , which is composed of crust and upper mantle . Extensional environments like the Basin and Range are characterized by listric normal faulting , or faults that level out with depth. Opposing normal faults link at depth producing a horst and graben geometry, where horst refers to

288-755: Is one small part of the much larger province. The Basin and Range Province includes much of western North America . In the United States, it is bordered on the west by the eastern fault scarp of the Sierra Nevada and spans over 500 miles (800 km) to its eastern border marked by the Wasatch Fault , the Colorado Plateau and the Rio Grande Rift . The province extends north to the Columbia Plateau and south as far as

324-429: Is suggested that this plate continued to be underthrust until about 19 Ma, at which time it was completely consumed and volcanic activity ceased, in part. Olivine basalt from the oceanic ridge erupted around 17 Ma and extension began. In addition to small amounts of Nevada petroleum , the Basin and Range Province supplies nearly all the copper and most of the gold , silver , and barite mined in

360-588: Is that the entire region between the Colorado River in the east and Baja California in the southwest (and bordered by various uplifts and mountains around the west-northwest-northern perimeters) has seen numerous cycles since at least the start of the Pleistocene (and perhaps up to 3  Ma ). In these cycles, pluvial lakes of varying size have come and gone in a complex cycle, mainly tied to changing climate patterns (particularly, glaciation during

396-644: The Gulf of California and Baja Peninsula with notably less faulting apparent in the Sierra Madre Occidental in the center of the southernmost Basin and Range Province. Common geographic features include numerous endorheic basins , ephemeral lakes, plateaus, and bolson valleys alternating with mountains (as described below). The area is mostly arid and sparsely populated, although there are several major metropolitan areas, such as Reno , Las Vegas , Salt Lake City , Phoenix , Tucson , El Paso — Ciudad Juárez , Mexicali , and Hermosillo . It

SECTION 10

#1732765123597

432-847: The Imperial Valley , in the United States, and the western side of the Mexicali Valley and the Colorado River Delta in Mexico. At 236 ft (72 m) below sea level, the Salton Sink is the topographic low area within the Salton Trough and is the second-lowest point, after Death Valley , on the North American continent. At 210 ft (64 m) below sea level, the Salton Sea , which fills

468-491: The Quaternary Period in the area, with an intertwined history of various larger bodies of water subsuming smaller ones during water table maxima and the subsequent splitting and disappearance thereof during the evaporative part of the cycles. Although these local cycles are now somewhat modified by human presence, their legacy persists; despite appearances much to the contrary, Death Valley actually sits atop one of

504-743: The Trans-Mexican Volcanic Belt in Mexico , though the southern boundaries of the Basin and Range are debated. In Mexico, the Basin and Range Province is dominated by and largely synonymous with the Mexican Plateau . Evidence suggests that the less-recognized southern portion of the province is bounded on the east by the Laramide Thrust Front of the Sierra Madre Oriental and on the west by

540-607: The mantle . The movement at this boundary divided the Pacific-Farallon Ridge and spawned the San Andreas transform fault , generating an oblique strike-slip component. Today, the Pacific plate moves north-westward relative to North America, a configuration which has given rise to increased shearing along the continental margin . The tectonic activity responsible for the extension in the Basin and Range

576-527: The Basin and Range and has led geologists to examine them as a group of related geologic features formed by crustal extension during the Cenozoic era (66.0 million years ago to present). The study of metamorphic core complexes has provided valuable insight into the extensional processes driving Basin and Range formation. Prior to the Eocene Epoch (55.8 ±0.2 to 33.9 ±0.1 Ma) the convergence rate of

612-529: The Basin and Range, metamorphic basement is visible at the surface. Some of these are metamorphic core complexes (MCC), an idea that was first developed based on studies in this province. A metamorphic core complex occurs when lower crust is brought to the surface as a result of extension. MCCs in the Basin and Range were not interpreted as being related to crustal extension until after the 1960s. Since then, similar deformational patterns have been identified in MCCs in

648-652: The Farallon and North American plates was fast, the angle of subduction was shallow, and the slab width was huge. During the Eocene the Farallon plate subduction -associated compressive forces of the Laramide , Sevier and Nevada orogenies ended, plate interactions changed from orthogonal compression to oblique strike-slip , and volcanism in the Basin and Range Province flared up ( Mid-Tertiary ignimbrite flare-up ). It

684-536: The Farallon plate had been consumed, and the seafloor spreading ridge that separated the Farallon plate from the Pacific plate ( Pacific-Farallon Ridge ) approached North America. In the Middle Miocene (15.97-11.63 million years ago), the Pacific-Farallon Ridge was subducted beneath North America ending subduction along this part of the Pacific margin; however, the Farallon plate continued to subduct into

720-709: The San Andreas Fault both terminate near the south end of the Salton Sea, in an area called the Brawley Seismic Zone . The Brawley Seismic Zone is an active spreading center that connects the San Andreas Fault system with the Imperial Fault Zone to the south. The Salton Trough is also referred to as a sedimentary basin because the basin has filled with sedimentary deposits as quickly as the basin has been sinking. In some areas,

756-665: The United States. Badwater Basin Badwater Basin is an endorheic basin in Death Valley National Park , Death Valley , Inyo County, California , noted as the lowest point in North America and the United States , with a depth of 282 ft (86 m) below sea level . Mount Whitney , the highest point in the contiguous United States , is only 84.6 miles (136 km) to

SECTION 20

#1732765123597

792-479: The basin due to their similarities. Adjacent to the pool, where water is not always present at the surface, repeated freeze–thaw and evaporation cycles gradually push the thin salt crust into hexagonal shapes. The pool is not the lowest point of the basin: the lowest point (which is only slightly lower) is several miles to the west and varies in position, depending on rainfall and evaporation patterns. The salt flats are hazardous to traverse (in many cases being only

828-474: The basin is flooded, some of the salt is dissolved; it is redeposited as clean crystals when the water evaporates. A popular site for tourists is the sign marking "sea level" on the cliff above the Badwater Basin. Similar to Owens Lake , it is characterized by a deep bed of unconsolidated valley fill from which the salt crust emerges. The current best understanding of the area's geological history

864-570: The density of the lithosphere and stimulates isostatic uplift as a consequence. Lithospheric regions characterized by elevated heat flow are weak and extensional deformation can occur over a broad region. Basin and Range extension is therefore thought to be unrelated to the kind of extension produced by mantle upwelling which may cause narrow rift zones, such as those of the Afar triple junction . Geologic processes that elevate heat flow are varied, however some researchers suggest that heat generated at

900-416: The inland Western United States and northwestern Mexico . It is defined by unique basin and range topography , characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. The physiography of the province is the result of tectonic extension that began around 17 million years ago in the early Miocene epoch. The numerous ranges within

936-633: The largest aquifers in the world. Throughout the Quaternary's wetter spans, streams running from nearby mountains filled Death Valley, creating Lake Manly , which during its greatest extents was approximately 80 mi (130 km) long and up to 600 ft (180 m) deep. Numerous evaporation cycles and a lack of outflow caused an increasing hypersalinity , typical for endorheic bodies of water. Over time, this hypersalinization, combined with sporadic rainfall and occasional aquifer intrusion, has resulted in periods of "briny soup", or salty pools, on

972-532: The lowest part of the Salton Sink, is the lowest permanent lake in North America. The Salton Trough is commonly subject to migrating earthquake swarms. The Salton Buttes , located within the Salton Sea, are rhyolite lava domes within the basin which were active 10,300 (± 1000) years BP . The Niland Geyser is one of dozens of mudpots and mud volcanoes in the Salton Trough but is the only one in

1008-456: The northwest. The site itself consists of a small spring -fed pool of "bad water" next to the road in a sink ; the accumulated salts of the surrounding basin make it undrinkable, thus giving it the name. The pool does have animal and plant life , including pickleweed , aquatic insects , and the Badwater snail . Badwater Crater , the lowest place on the planet Mars , is named after

1044-501: The numerous recent Ice Age cycles ), but also influenced by the progressive depositing of alluvial plains and deltas by the Colorado River, as can also be seen in the case of the Salton Sea . These alternate with periodic water body breakthroughs and rearrangements due to erosion and the proximity of the San Andreas Fault . This process has resulted in a high number of evaporating and reforming endorheic lakes throughout

1080-996: 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 , and the Sandia Mountains . 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 −282 feet (−86 m). The province's climate

1116-486: The sediment is more than 20,000 ft (6,100 m) deep. Sources of the sediment are the mountainous areas that surround the trough, and the Colorado River , which in the past fed Lake Cahuilla , a large inland freshwater lake that disappeared after the Colorado River changed course to the Gulf of California. Basin and Range Province The Basin and Range Province is a vast physiographic region covering much of

Salton Trough - Misplaced Pages Continue

1152-476: The southern Basin and Range and propagated north over time. Clarence Dutton famously compared the many narrow parallel mountain ranges that distinguish the unique topography of the Basin and Range to an "army of caterpillars crawling northward." The tectonic mechanisms responsible for lithospheric extension in the Basin and Range province are controversial, and several competing hypotheses attempt to explain them. Key events preceding Basin and Range extension in

1188-463: The total extension of the region; however, the median estimate is about 100% total lateral extension. Total lateral displacement in the Basin and Range varies from 60 to 300 km since the onset of extension in the Early Miocene with the southern portion of the province representing a greater degree of displacement than the north. Evidence exists to suggest that extension initially began in

1224-429: The upthrown fault block and graben to the down dropped fault block. The average crustal thickness of the Basin and Range Province is approximately 30–35 km and is comparable to extended continental crust around the world. The crust in conjunction with the upper mantle comprises the lithosphere . The base of the lithosphere beneath the Basin and Range is estimated to be about 60–70 km. Opinions vary regarding

1260-514: The western United States include a long period of compression due to the subduction of the Farallon plate under the west coast of the North American continental plate which stimulated the thickening of the crust. Most of the pertinent tectonic plate movement associated with the province occurred in the Neogene period (23.03-2.58 million years ago) and continues to the present. By the Early Miocene sub-epoch (23.03-15.97 million years ago), much of

1296-637: The world known to have moved significantly, affecting the Union Pacific Railroad , California State Route 111 , and other infrastructure since 2018. The Salton Trough is a result of crustal stretching and sinking caused by the combined actions of the San Andreas Fault and the East Pacific Rise , particularly the Gulf of California Rift Zone (GCRZ), the northernmost portion of the East Pacific Rise. The GCRZ and

#596403