The Salton Trough is an active

tectonic Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons. These processes ...

pull-apart basin, or

graben In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...

. It lies within the Imperial, Riverside, and

San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...

counties of southeastern

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and extends south of the

Mexico–United States border The international border separating Mexico and the United States extends from the Pacific Ocean in the west to the Gulf of Mexico in the east. The border traverses a variety of terrains, ranging from urban areas to deserts. It is the List of ...

into the state of

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

Description

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 The San Gorgonio Pass, or Banning Pass, is a elevation Gap (landform), gap on the rim of the Great Basin between the San Bernardino Mountains to the north and the San Jacinto Mountains to the south. The pass was formed by the San Andreas Faul ...

in Riverside County and extends southeast to the Gulf of California. Major geographical features located in the trough include the

Coachella Valley The Coachella Valley ( ) is an arid rift valley in the Colorado Desert of Southern California in Riverside County. The valley has been referred to as Greater Palm Springs and occasionally the Palm Springs Area due to the historic promine ...

, the

Salton Sea The Salton Sea is a shallow, landlocked, highly salinity, saline endorheic lake in Riverside County, California, Riverside and Imperial County, California, Imperial counties in Southern California. It lies on the San Andreas Fault within the S ...

, and the Imperial Valley, in the United States, and the western side of the Mexicali Valley and the Colorado River Delta in Mexico. At below sea level, the Salton Sink is the topographic low area within the Salton Trough and is the second-lowest point, after

Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. It is thought to be the Highest temperature recorded on Earth, hottest place on Earth during summer. Death Valley's Badwat ...

, on the North American continent. At below sea level, the

, which fills 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 Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

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 the world known to have moved significantly, affecting the

Union Pacific Railroad The Union Pacific Railroad is a Railroad classes, Class I freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United Stat ...

, California State Route 111, and other infrastructure since 2018.

Geology

The Salton Trough is a result of crustal stretching and sinking caused by the combined actions of the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

and the East Pacific Rise, particularly the Gulf of California Rift Zone (GCRZ), the northernmost portion of the East Pacific Rise. The GCRZ and 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.Fuis, Cary S. and Walter D. Mooney
''Salton Trough'' Lithospheric Structure and Tectonics from Seismic-Refraction and Other Data
in USGS Professional Paper 1515] The Salton Trough is also referred to as a

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock They form when long-term subsidence ...

because the basin has filled with sedimentary deposits as quickly as the basin has been sinking. In some areas, the sediment is more than deep. Sources of the sediment are the mountainous areas that surround the trough, and the

Colorado River The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...

, 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.

References

{{California Faults Pull-apart basins Colorado Desert Geologic provinces of California Geology of Imperial County, California Geology of Riverside County, California Geology of San Diego County, California Geological depressions in the United States Physiographic sections Physiographic regions of the United States *Trough Geography of Baja California