Soda Lake is a shallow, ephemeral,

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

endorheic lake An endorheic lake (also called a sink lake or terminal lake) is a collection of water within an endorheic basin, or sink, with no evident outlet. Endorheic lakes are generally saline as a result of being unable to get rid of solutes left in the l ...

in the Carrizo Plain in southeastern

San Luis Obispo County, California San Luis Obispo County (), officially the County of San Luis Obispo, is a County (United States), county on the Central Coast (California), Central Coast of California. As of the 2020 United States Census, 2020 census, the population was 282, ...

. The lake is located on the southwest side of the northern Carrizo Plain, east of

San Luis Obispo San Luis Obispo (; Spanish for " St. Louis the Bishop", ; Chumash: ''tiłhini'') is a city and county seat of San Luis Obispo County, in the U.S. state of California. Located on the Central Coast of California, San Luis Obispo is roughly halfwa ...

. It can be reached by Soda Lake Road, which runs northwest–southeast between State Route 166 and State Route 58. The lake is at an elevation of and covers an area of about .

Endorheic drainage basin

Internal drainage of the Carrizo Plain and the formation of Soda Lake began during

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

time when

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...

deformation associated with the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...

defeated a

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

that once drained the valley. An originally fresh to brackish water lake probably persisted through much of the Pleistocene during which coastal California was wetter and cooler than now. Diminished

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

and a higher

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

rate led to shrinkage of the ancestral lake and associated increased

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

which set the stage for clay dune formation. About 30% of the closed or

endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, t ...

is to the north of the lake and 70% is south of it. The Soda Lake complex consists of two larger basins, and at least 130 smaller pans. The large L-shaped northern basin is about 10.5 km² in area. The remaining basins, including both those that feed the northern basin and those that have no surface outlets, comprise an area of about 4.8 km². Water levels in the basins rise and fall seasonally. Rainfall on the Carrizo Plain is only about 20 cm in an average year but is higher on the surrounding mountains. Following exceptionally wet winters, typically

El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date L ...

years, the large northern and southern basins do not evaporate completely, although the water retreats toward the center of the basin leaving a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

crust up to 20 cm thick. Most of the large and small pans are fringed by

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

dunes. It is one of the largest alkali

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

s remaining in natural condition in

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It supports

fairy A fairy (also fay, fae, fey, fair folk, or faerie) is a type of mythical being or legendary creature found in the folklore of multiple European cultures (including Celtic, Slavic, Germanic, English, and French folklore), a form of spirit, ...

and

brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th century AD from Urmia La ...

, as well as migratory and nesting

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s. A

boardwalk A boardwalk (alternatively board walk, boarded path, or promenade) is an elevated footpath, walkway, or causeway built with wooden planks that enables pedestrians to cross wet, fragile, or marshy land. They are also in effect a low type of bridge ...

was built along the shore to prevent damage to the

saltbush Saltbush is a vernacular plant name that most often refers to ''Atriplex'', a genus of about 250 plants distributed worldwide from subtropical to subarctic regions. ''Atriplex'' species are native to Australia, North and South America, and Eurasia. ...

habitat that borders the lake.

Dunes

The largest

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

bounds the eastern and southern edges of the northern basin. This dune is up to 470 m wide, 16.7 m high, and nearly 9.5 km in length. Part of the dune is active, receiving

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

from the mud flat exposed between the dune and the salt pan. Most of the eastern (north-south) leg of the dune, which is lower and narrower, is currently inactive. Westward retreat of the shoreline exposed the former lake flat to colonization and stabilization by salt-resistant plants. Thenardite-215859

Notes

References

United States Bureau of Land Management - Carrizo Plain National Monument

External links

{{Commons category, Soda Lake (San Luis Obispo County)
Virtual Guidebooks - Panoramas of Soda Lake
Landforms of San Luis Obispo County, California Endorheic lakes of California Dunes of California Bodies of water of San Luis Obispo County, California

Endorheic drainage basin

Dunes

See also

Notes

References

External links