The Salton Sink is the low point of an

endorheic basin An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...

, a closed drainage system with no outflows to other bodies of water, in the Colorado Desert sub-region of the Sonoran Desert. The sink falls within the larger Salton Trough and separates the Coachella Valley from the Imperial Valley, which are also segments of the Salton Trough. The lowest point of the sink is below sea level, and since 1906 the Salton Sea has filled the lowest portion of the sink to a water depth of up to .

Geology

The Salton Sink is the topographic low area within the Salton Trough, 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. The Salton Trough is a result of crustal stretching and sinking by the combined actions of the San Andreas Fault and the East Pacific Rise. The Brawley seismic zone forms the southeast end of the basin and connects the San Andreas Fault system with the Imperial Fault Zone to the south. The Salton Buttes 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.

History

A large lake, Lake Cahuilla, existed in the area from about 20,500 to 3,000 years ago and left evidence as wave-cut benches on the higher portions of the Salton Buttes. A beach mark outlines the shoreline of ancient Lake Cahuilla where archeologists found rock fish traps and charred remains of razorback sucker and bonytail bones. High water lines suggest the basin has filled many times, creating a lake some in length and nearly deep. Its most recent incarnation is evidenced by fish traps found some below the high-water mark that were estimated to be between 300 and 1,000 years old. In recent times, the 1862 Colorado River flood waters reached the Salton Sink, filling it and creating a lake some long and wide. In 1884 and 1891 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 ...

had escapement flow into the Salton Sink. The 1891 flood created a lake that covered an area long and wide. A larger 1905 Colorado flood escaped into a diversion canal, forming the Alamo and New Rivers and creating the current Salton Sea in the sink's Coachella Valley.“A Sea in the Making in the Southland“ in ''The Salton Sea California's Overlooked Treasure''
/ref> A 1907 dam prevents flood escapements, but leakage still occurs to the Salton Sea.

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References

{{California Faults, state=collapsed Endorheic basins of the United States Geography of the Colorado Desert Geography of Imperial County, California Geography of Riverside County, California Coachella Valley Imperial Valley Salton Sea Salton Trough Geology of Imperial County, California Geology of Riverside County, California