Lake Cahuilla ( ; also known as Lake LeConte and Blake Sea) was a prehistoric lake 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 ...

and northern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. Located in the

Coachella Coachella may refer to: * Coachella, California * Coachella Canal, in California * Coachella (festival), an annual music and arts festival in California * "Coachella – Woodstock in My Mind", a 2017 song by Lana del Rey See also

* Coachell ...

and

Imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imperial, Nebraska * Imperial, Pennsylvania * Imperial, Texa ...

valleys, it covered surface areas of to a height of above sea level during the

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 ...

. During earlier stages of the

Pleistocene 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 ...

, the lake reached even higher elevations, up to above sea level. During the Holocene most of the water came from the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

with little contribution from local runoff; in the Pleistocene local runoff was higher and it is possible that Lake Cahuilla was supported solely from local water sources during the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...

. The lake overflowed close to

Cerro Prieto Cerro Prieto ( coc, Wee Ñaay, eng, "Black Hill") is a volcano located approximately 29 km (18 mi) SSE of Mexicali in the Mexican state of Baja California. The volcano lies astride a spreading center associated with the East Pacific R ...

into the Rio Hardy, eventually draining into the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

. The lake formed several times during the Holocene, when water from the Colorado River was diverted into the

Salton Trough The Salton Trough is an active tectonic pull-apart basin, or graben. It lies within the Imperial, Riverside, and San Diego counties of southeastern California, United States and extends south of the Mexico–United States border into the state of ...

. This tectonic depression forms the northern basin of the Gulf of California, but it was separated from the sea proper by the growth of the

Colorado River Delta The Colorado River Delta is the region where the Colorado River flows into the Gulf of California (also known as the Sea of Cortez) in eastern Mexicali Municipality in the north of the state of Baja California in northwesternmost Mexico. The ...

. Such changes in river courses may have been caused by

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s among the numerous faults that cross the region, such as 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 ...

. Conversely, it is possible that the weight of the water itself triggered earthquakes. During its existence, Lake Cahuilla formed strandlines and various beach deposits such as gravel bars and

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a pro ...

deposits. The lake existed in several stages over the last 2,000 years, periodically drying and refilling and eventually disappearing sometime after 1580. Between 1905 and 1907, due to an engineering accident, the

Salton Sea The Salton Sea is a shallow, landlocked, highly saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California. It lies on the San Andreas Fault within the Salton Trough that stretches to the Gulf o ...

formed in parts of the lower basin of Lake Cahuilla. Were it not for human intervention, the sea might have grown to the size of prehistoric Lake Cahuilla. Today the former lake bed forms the fertile regions of the Imperial and Coachella Valleys. The

Algodones Dunes The Algodones Dunes is a large sand dune field, or erg, located in the southeastern portion of the U.S. state of California, near the border with Arizona and the Mexican state of Baja California. The field is approximately long by wide and ex ...

were formed from sand deposited by Lake Cahuilla, which was transported by wind toward the area. During its existence, the lake supported a rich biota with fish,

bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

and vegetation on its shorelines. These resources supported human populations on its shores, as evidenced by a number of archeological sites and mythological references to the lake in the traditions of the

Cahuilla The Cahuilla , also known as ʔívil̃uqaletem or Ivilyuqaletem, are a Native American people of the various tribes of the Cahuilla Nation, living in the inland areas of southern California.William Phipps Blake William Phipps Blake (June 1, 1826 – May 22, 1910) was an American geologist, mining consultant, and educator. Among his best known contributions include being the first college trained chemist to work full-time for a United States chemical ...

. The lake is named after the

Cahuilla The Cahuilla , also known as ʔívil̃uqaletem or Ivilyuqaletem, are a Native American people of the various tribes of the Cahuilla Nation, living in the inland areas of southern California. A second name is "Blake Sea", after William Phipps Blake. The Cahuilla themselves named the lake ''paul'', and their mythology states that when their creator ''paulnevolent'' was cremated, tears turned the lake salty. The name "Lake LeConte" was coined in 1902 by Gilbert E. Bailey, and it is occasionally used to refer to the lake that existed during the

or Pleistocene. In 1980, M.R. Waters applied the term to cover all lakes of Holocene age in the Salton Basin. This name is derived from

Joseph LeConte Joseph Le Conte (alternative spelling: Joseph LeConte) (February 26, 1823 – July 6, 1901) was a physician, geologist, professor at the University of California, Berkeley and early California conservationist. Early life Of Huguenot descent, h ...

, a geography professor. Presently, the name "Lake Cahuilla" applies to the

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

at the northern end of the

Coachella Canal The Coachella Canal is a aqueduct that conveys Colorado River water for irrigation northwest from the All-American Canal to the Coachella Valley north of the Salton Sea in Riverside County, California. The canal was completed in 1949 and is cur ...

, in the Coachella Valley. "Lake Cahuilla" is also the name of a seismic station in California.

Geography

Lake Cahuilla formed in the region of the present-day

. It extended over the southern end of Coachella Valley in the north, through the

Imperial Valley , photo = Salton Sea from Space.jpg , photo_caption = The Imperial Valley below the Salton Sea. The US-Mexican border runs diagonally across the lower left of the image. , map_image = Newriverwatershed-1-.jpg , map_caption = Map of Imperial ...

in the south, and down to the

area in

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

. The general area is also known as the

Colorado Desert California's Colorado Desert is a part of the larger Sonoran Desert. It encompasses approximately , including the heavily irrigated Coachella and Imperial valleys. It is home to many unique flora and fauna. Geography and geology The Colorado De ...

. Currently, of the land is below sea level. The

extends northwest and has a width of at the border. Towns in areas formerly covered by Lake Cahuilla include, from north to south,

Indio Indio may refer to: Places * Indio, Bovey Tracey, an historic estate in Devon, England * Indio, California, a city in Riverside County, California, United States People with the name * Indio (musician), Canadian musician Gordon Peterson * Índio ...

Thermal A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

Mecca Mecca (; officially Makkah al-Mukarramah, commonly shortened to Makkah ()) is a city and administrative center of the Mecca Province of Saudi Arabia, and the Holiest sites in Islam, holiest city in Islam. It is inland from Jeddah on the Red ...

, Mortmar, Niland,

Calipatria Calipatria (portmanteau of ''California'' and ''Patria'', Spanish for "homeland") is a city in Imperial County, California. Calipatria is located north of El Centro. It is part of the El Centro Metropolitan Area. The population was 6,515 a ...

, Brawley,

and

El Centro El Centro (Spanish for "The Center") is a city and county seat of Imperial County, California, United States. El Centro is the largest city in the Imperial Valley, the east anchor of the Southern California Border Region, and the core urban are ...

Calexico Calexico () is a city in southern Imperial County, California. Situated on the Mexican border, it is linked economically with the much larger city of Mexicali, the capital of the Mexican state of Baja California. It is about east of San Diego ...

and

Mexicali Mexicali (; ) is the capital city of the Mexican state of Baja California. The city, seat of the Mexicali Municipality, has a population of 689,775, according to the 2010 census, while the Calexico–Mexicali metropolitan area is home to 1,000, ...

may have been covered as well. To the southeast, the New River and the

Alamo River The Alamo River ( es, Río Álamo) flows west and north from the Mexicali Valley (Baja California) across the Imperial Valley (California). The river drains into the Salton Sea. The New River, Alamo River, and the Salton Sea of the 21st century ...

now flow through the dry lakebed, while the Whitewater River and the San Felipe Creek enter from the northwest and southwest, respectively. Major shorelines existed at above

North American Datum The North American Datum (NAD) is the horizontal datum now used to define the geodetic network in North America. A datum is a formal description of the shape of the Earth along with an "anchor" point for the coordinate system. In surveying, ca ...

(NAD) and at above NAD. With a southern shore south of the US-Mexico border, Lake Cahuilla had a length of , a maximum width of and reached a depth of approximately at a water elevation of . The maximum surface area was about . The lake at maximum level held about of water. At maximum size, Lake Cahuilla was considerably larger than the Salton Sea and almost as large as the entire Salton Trough, and constituted one of the largest lakes of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Bat Caves Butte and Obsidian Butte formed islands in the lake when it was full although during highstands the latter was submerged. Relatively straight northwest–southeast trending eastern shores faced from northwest to southeast the

Indio Hills The Indio Hills are a low mountain range in the Colorado Desert. located in Riverside County, California's Coachella Valley. The hills were named for their proximity to the city of Indio, and are sometimes referred to as the Indio Mud Hills or ...

, the Mecca Hills, the

Orocopia Mountains The Orocopia Mountains are located in Riverside County in southern California, United States, east of the Coachella Valley, west of the Chuckwalla Mountains, and south of Interstate 10 in the Colorado Desert. The range lies in an east-west dire ...

, the

Chocolate Mountains The Chocolate Mountains of California are located in Imperial County, California, Imperial and Riverside County, California, Riverside counties in the Colorado Desert of Southern California. The mountains stretch more than 60 miles (100 km) ...

and the East Mesa. The less regular western shore faced the Santa Rosa Mountains towards north and the

Fish Creek Mountains The Fish Creek Mountains are a mountain range in Lander County, Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona ...

and

Vallecito Mountains The Vallecito Mountains are located in the Colorado Desert, in eastern San Diego County, Southern California. They are about north of the U.S. border with Mexico. Geography The mountains lie in Anza-Borrego Desert State Park, in an east–west ...

farther south. Earlier lake stages may have extended into the

Jacumba Mountains The Jacumba Mountains are a mountain range of the Peninsular Ranges system, located in eastern San Diego County, Southern California, near the U.S. border with Mexico. The mountain range lies in a northwest-southeasterly direction, east of the I ...

as well.

Hydrology

Inflow

Lake Cahuilla was formed by water from the

;

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...

and other inflows were negligible. Likewise, the precipitation (presently about ) did not contribute much to the lake budget. The amount of water needed to sustain Lake Cahuilla at a level of above sea level is possibly about half of the discharge of the Colorado River, and during times where the lake was filling nearly no water from the river would have reached the

Sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

of the Colorado River Delta directed water into the Lake Cahuilla area, a process that was more likely to happen during humid periods.

Distributaries A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distributar ...

in a

river delta A river delta is a landform shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, res ...

are inherently unstable and tend to change course often. Major floods may have triggered the change in river course, although most of the flood events in the prehistoric record do not appear to be associated with diversions to Lake Cahuilla and one cannot conclude that the river course changes are more likely to occur during wet periods. Given that the slope toward Lake Cahuilla is steeper than the one toward the Gulf of California, once the river entered the basin it likely stabilized on that course. In fact, it is remarkable that this slope difference doesn't regularly cause the river to enter the Salton Trough. The diversions occurred close to the apex of the Colorado River Delta and would have discharged water directly through the

and indirectly through Volcano Lake and the New River into Lake Cahuilla. The infilling of the lake may have been a catastrophic flood, considering that native people fled the

to the mountains. Infilling to an altitude of above sea level would have taken 12–20 years. When the lake was full, the Colorado River would have entered it at the southeastern side. When the Colorado River drained into Lake Cahuilla, the entire sediment flow ( ) of the river would have entered the lake; a sedimentation rate of has been inferred for the northern part of the lake while the Colorado River Delta shows evidence of reduced sedimentation while the river drained into Lake Cahuilla. Sedimentation of the inlet during highstands and resulting river course changes away from Lake Cahuilla would have resulted in the Colorado River changing its course back to the Gulf of California. Other major streams that drained into Lake Cahuilla were Whitewater River from the north, and San Felipe Creek and Carrizo Creek from the southwest. More minor drainage came from Arroyo Salado on the western shore, and Salt Creek and Mammoth Wash on the eastern shore. Additional unnamed drainages did exist. Drainage from the

and the Cargo Muchacho Mountains may have reached the lake but are now buried by the

. All these water systems are

ephemeral Ephemerality (from the Greek word , meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and experiences, fr ...

. Presently the only major streams entering the basin come from mountains to the west and northwest, but during the Pleistocene they likely transported more water. When lower sea levels entrenched a more southerly course of the Colorado River, Lake Cahuilla may have been nourished solely by local runoff during the Wisconsin glaciation.

Shorelines

Shorelines lie at altitudes of above sea level; the variation is probably caused by slumping, measurement problems, and different wave cut and beach deposit thicknesses. The most recent highstand lasted long enough to allow the formation of well developed shorelines. Fish fossils found off the coastline suggest that

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...

s connected to the lake formed there. Fluctuations of the lake level caused the deposition of beach berms. Based on recessional shorelines with distances of slightly over from each other, of depth would have evaporated in about 70 years. The shoreline is particularly visible at Travertine Point in the Santa Rosa Mountains, where the color contrast between the dark desert varnish above the shoreline and the

below is recognizable from US highway 99. The nature of the shoreline varies; to the east it includes high wavecut cliffs beneath the Mecca Hills over

baymouth bar A baymouth bar is a depositional feature as a result of longshore drift. It is a sandbank that partially or completely closes access to a bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water ...

s farther south, one of which reaches a length of at the Orocopia Mountains. Even farther south

shingle beach A shingle beach (also referred to as rocky beach or pebble beach) is a beach which is armoured with pebbles or small- to medium-sized cobbles (as opposed to fine sand). Typically, the stone composition may grade from characteristic sizes ranging ...

es are found, showing evidence of vigorous wave activity. At East Mesa, a long

barrier beach Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a ...

may have formed from sediments deposed by

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing o ...

s. Material eroded from the eastern and southwestern shores was deposited in the form of

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

and sand bars off the coast. As lake levels rose, at least one tributary stream had its valley filled in with Lake Cahuilla sediments.

Tufa Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertine. ...

s formed along shorelines, reaching maximum thicknesses of ; they are found especially on the northwestern shores. At the

, beaches made up of gravel and a travertine layer on the mountain front mark the shore.

Water composition

As deduced from the presence of freshwater

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s, Lake Cahuilla was a freshwater lake during its highstand, while lower lake level stages show fossil evidence of increased salinity. Alternatively the lake may have been

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

. The salinity may have been lower where the Colorado entered the lake and higher farther north.

Water currents

High cliffs, sandbars and piles of pebbles testify to the existence of strong wave action on the northeastern shore, which was influenced by strong northwesterly winds. Inversely, the gentle southern slopes of the lake bed probably reduced wave action on the lake's southern shores. Strong northwesterly winds likely created southbound lake currents on the eastern shores, forming beach structures from sediment imported from the north into the lake.

Outflow

Only about half of the discharge of the Colorado River was needed to sustain Lake Cahuilla; the rest drained across the delta into the Gulf of California. A above sea level outflow sill close to Cerro Prieto formed the likely spillway for the lake. Other data points to a sill height of , but topographic maps of the area are not very precise. The present day sill is about long, and Cerro Prieto lies on the

drainage divide A drainage divide, water divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a singl ...

between the New River and Rio Hardy watersheds. Water reached the Gulf of California through the present day Rio Hardy channel.

Oxygen-18 Oxygen-18 (, Ω) is a natural, stable isotope of oxygen and one of the environmental isotopes. is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceu ...

isotope data from tufas suggests that the lake was closed or mostly closed for much of its time, that the outflow did contribute little to the water balance; some water may also have been trapped in

aquifers An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

. The present-day sill to the Gulf of California lies at an altitude of above sea level; the sill was probably higher in the past given that the highest shorelines of Lake Cahuilla are above sea level. During the Pleistocene, the sill was even higher and thus lake levels could reach higher elevations. A rejuvenation of the river triggered by decreasing sea levels or tectonic subsidence at Cerro Prieto caused the levels of the various lakes to progressively decrease.

Dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyol ...

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

s from the

volcano may have stabilized the overflow sill against erosion; it is otherwise difficult to explain why the fairly easily eroded sill material was stable against downcutting by overflow. Once cut off from the Colorado River by changes in its course, Lake Cahuilla would have evaporated at a rate of , eventually drying in 53 years. Data taken from fossil ''

Mugil cephalus The flathead grey mullet (''Mugil cephalus'') is an important food fish species in the mullet family Mugilidae. It is found in coastal tropical and subtropical waters worldwide. Its length is typically . It is known with numerous English names ...

'' suggest that during the recession of the lake, the Colorado River still occasionally reached the lake.

Climate

The present day climate of the Lake Cahuilla area is dry and hot during summer. Temperatures range from with a high of . Precipitation amounts to . The mountains west of the Cahuilla area are considerably wetter. Evaporation rates can reach . Winds on the lake probably occurred in two patterns, northwesterly winds with speeds of and more persistent westerly winds with speeds of . These winds formed substantial waves in the lake and created

longshore current Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle) along a coast parallel to the shoreline, which is dependent on the angle incoming wave direction ...

s along the eastern shores of Lake Cahuilla. Pleistocene climate is harder to determine, though it was probably not much wetter than today, except in the mountains where precipitation increased. Drainage changes in the Colorado River Delta probably account for most of the water budget increases responsible for the formation of Lake Cahuilla. In the

Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...

large lakes also formed during that time. In the early Holocene the

North American Monsoon The North American monsoon, variously known as the Southwest monsoon, the Mexican monsoon, the New Mexican monsoon, or the Arizona monsoon is a pattern of pronounced increase in thunderstorms and rainfall over large areas of the southwestern Uni ...

strongly influenced the local climate and then progressively weakened. A colder climate introduced cold-limited animal species which appeared at lower altitudes, and

glaciers A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

formed on the

San Bernardino Mountains The San Bernardino Mountains are a high and rugged mountain range in Southern California in the United States. Situated north and northeast of San Bernardino and spanning two California counties, the range tops out at at San Gorgonio Mountain � ...

. A probable southward shift of the storm belts led to windier weather. According to data obtained from tufa in Lake Cahuilla, a wet period ended 9,000 years

before present Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becaus ...

, and between 6,200 and 3,000–2,000 years before present extended droughts occurred.

Geology

Lake Cahuilla formed in a region where the Gulf of California tectonic zone meets 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 ...

tectonic system. Volcanic activity and earthquakes occur as a consequence to this tectonic configuration. The San Andreas Fault runs roughly parallel to the northeastern margin of Lake Cahuilla, where it moved at a rate of over the last 45,000–50,000 years. Earthquakes are documented in sediments from Lake Cahuilla, but this southern segment has not ruptured in historical time. Tectonic extension occurs at the points where the fault forms stepovers, although the extensional structures are still relatively immature. The Cahuilla Basin, also known as the

Salton Sink The Salton Sink is the low point of an endorheic basin, 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 ...

, is part of the trough that is occupied by the Gulf of California. The basin structure is surrounded by various crystalline rocks that were formed from the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

era forwards to the

Tertiary period Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

. About of sediment fill the basin from the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

, testifying to rapid tectonic subsidence. Four million years ago, the Colorado River started to enter into the area, and the formation of the Colorado River Delta separated the Salton Trough during the Pleistocene from the Gulf of California; during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Laguna Salada Laguna Salada (, ''Salt Lake'') is a municipality (''municipio'') of the Valverde province in the Dominican Republic. Within the municipality there are three municipal districts (''distritos municipal''): Cruce de Guayacanes, Jaibón and La ...

, with yet smaller basins such as the Mesquite Basin also reported. Approximately of sediment have accumulated in the Salton Trough, burying the underlying crust.

Heat flow Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

analysis suggests that active extension is underway in the trough.

Faults and earthquakes

When Lake Cahuilla existed, individual earthquakes caused as much as displacement. Sediments of Lake Cahuilla have shown deformation structures similar to these formed by the

1971 San Fernando earthquake The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a magnitude o ...

in the Van Norman Reservoir of the

Los Angeles Aqueduct The Los Angeles Aqueduct system, comprising the Los Angeles Aqueduct (Owens Valley aqueduct) and the Second Los Angeles Aqueduct, is a water conveyance system, built and operated by the Los Angeles Department of Water and Power. The Owens Valley ...

. These deformation structures were formed by

soil liquefaction Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in ...

. Sediments of the lake Coachella have yielded evidence of eight earthquakes, dated to have occurred between 906 – 961, 1090 – 1152, 1275 – 1347, 1588 – 1662, and 1657 – 1713. Less certain is the timing of events between 959 – 1015 and 1320 – 1489. Patterns of seismic activity detected by paleoseismology suggest that the filling of Lake Cahuilla might have triggered stress changes that caused earthquakes along the San Andreas Fault and other faults when they were already close to rupture. Such lake-induced seismicity is known from

s and referred to as

induced seismicity Induced seismicity is typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust. Most induced seismicity is of a low magnitude. A few sites regularly have larger quakes, such ...

. Alternatively, earthquakes could have caused course changes in the Colorado River that then caused the lake to flood or to dry up; paleoseismology in

* Coachell ...

is consistent with this hypothesis. Some earthquakes such as the 1892 Laguna Salada earthquake caused large vertical displacements that could have triggered flooding. Conversely, tectonically driven uplift of the northern side of the Colorado River Delta tends to stabilize the present southward course of the river against diversions to the north. USGS map of Imperial fault zone

The

has offset Indian stone rings, its path is buried by sediments from Lake Cahuilla. During the Pleistocene, this fault was relatively inactive compared to the

Imperial Fault The Imperial Fault Zone is a system of geological faults located in Imperial County in the Southern California region, and adjacent Baja California state in Mexico. It cuts across the border between the United States and Mexico. Geology The I ...

and the

San Jacinto Fault The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and i ...

. Other faults that crossed the shores of Lake Cahuilla are: * The Extra fault zone, which divides a northern more stable basin from a southern basin that underwent tectonic extension and slightly slower sedimentation. * The Coyote Creek Fault, whose movement rate has been estimated from displacement of Lake Cahuilla sediments and probably accelerated during the time of Cahuilla's highstand. * The Superstition Mountain Fault which extends from the Coyote Creek fault. * The San Jacinto Fault which runs parallel to part of Cahuilla's western shore, was last active in 820–1280, 1280, 1440–1637 and 1440–1640 and whose fault trace could be buried beneath sediments from Lake Cahuilla. * The

Elmore Ranch fault Elmore may refer to: Places United States *Elmore, Alabama *Elmore County, Alabama *Elmore County, Idaho *Elmore, Illinois *Elmore, Minnesota * Elmore Township, Minnesota *Elmore, Ohio *Elmore City, Oklahoma *Elmore, Vermont **Lake Elmore *Elmore, ...

which displays evidence of after-lake activity in the Superstition Hills. Faults on the lake floor include the

Brawley Seismic Zone The Brawley Seismic Zone (BSZ), also known as the Brawley fault zone, is a predominantly extensional tectonic zone that connects the southern terminus of the San Andreas Fault with the Imperial Fault in Southern California. The BSZ is named for ...

, potentially the

Cerro Prieto Fault The Cerro Prieto Fault is a transform fault located in far northern Baja California. It runs between the Cerro Prieto spreading center located southwest of Mexicali, and the Wagner Basin, another spreading center which lies under the Gulf of Cal ...

, the Imperial Fault, and the Kane Springs Faults. The Imperial Fault may have ruptured together with a rupture of the San Andreas Fault during a highstand of Lake Cahuilla, and was last active during the 1940 Imperial Valley earthquake.

Volcanoes

Several volcanoes existed on the floor of Lake Cahuilla and are now emergent at the southeastern margin of the Salton Sea, including the Cerro Prieto and the

Salton Buttes The Salton Buttes are a group of volcanoes in California, on the Salton Sea. They consist of a -long row of five lava domes, named Mullet Island, North Red Hill, Obsidian Butte, Rock Hill and South Red Hill. They are closely associated with a ...

. Cerro Prieto is formed by two high

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...

s that coalesce into a volume of about and a wide crater on the northeastern dome. In addition,

mud pot A mudpot, or mud pool, is a sort of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud. The acid and microorganisms decompose surrounding rock into clay and mud. Description The mud of a mud ...

s and

mud volcano A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce la ...

es exist on the floor of the Cahuilla Basin. Geothermal energy is obtained in some parts of the region. The presence of volcanism may have been facilitated by extensional faults, which would have provided pathways for magma ascent. The Salton Buttes are five lava domes that form a long chain; each dome is less than wide. They are formed by rhyolite, which contains xenoliths. These domes are known as Mullet Hill, Obsidian Butte, Red Island and Rock Hill. Obsidian Butte originally formed subaerially but tufas and Wave-cut platform, wavecut forms show that Lake Cahuilla submerged the dome. Red Island erupted within Lake Cahuilla, forming pyroclastic flow deposits. Wave action removed pumice and probably formed Sand bar, beach bars from this volcano. Pumice rafts are found emplaced on local shorelines. Potassium-argon dating has yielded ages of 16,000 years ago for the Salton Buttes, later superseded by an age estimate of 33,000 ± 35,000 years ago and finally with a date of 2,480 ± 470 years before present on the basis of uranium-thorium dating. Despite these old ages, some of them still release steam. Cerro Prieto appears to be 108,000 ± 46,000 years old based on potassium-argon dating, but legends of native Cocopah, Cucupah people may indicate Holocene activity. Obsidian from Obsidian Butte has been found as far as away. It started being used between 510 BC-640 AD, which led to the theory that the Obsidian Butte could only be used as a source of obsidian once it was no longer covered by Lake Cahuilla. Obsidian Butte was underwater during the highstands, but at lower water levels it would have formed an island in Lake Cahuilla. During the late historical period it was a source of obsidian for southernmost California. File:Salton Buttes - Obsidian Butte from access road.JPG, Obsidian Butte File:Salton Buttes - Mullet Island from Red Island.JPG, Mullet Island File:Salton Buttes - Red Island and Rock Hill from Obsidian Butte - closeup.JPG, Red Island and Rock Hill

Biology

Bivalves occurred at the shores of Lake Cahuilla, including ''Anodonta californiensis'' and possibly ''Pisidium casertanum''. ''Anodonta'' shells are sometimes found within their own tunnels. They were probably used by inhabitants as a food source or to make shell beads. Gastropods identified include ''Amnicola longinqua'', ''Gyraulus parvus'', ''Helisoma trivolvis'', ''Physella ampullacea'', ''Physella humerosa'' and ''Tryonia protea''. These taxa were relatively abundant at the shores of the lake. Ostracods include ''Cypridopsis vidua'', ''Cyprinotus torosa'' and ''Limnocythere ceriotuberosa''. Sponges have been identified in fossil deposits as well. One mammal found in the lake was the muskrat, ''Ondatra zibethicus''. The lake formed an oasis in the desert. The shores of Lake Cahuilla developed arrowweed, tules and Willow weed, willowweed, with mesquite at distance to the shoreline and microbial mats underwater. Land plants identified in Lake Cahuilla sediments include evening primroses, pine, Polypodiaceae, ragweed, saltbushes, ''Selaginella sinuites'' and sunflower. Many of these are represented by pollen. The Pleistocene lake and adjacent lagoons featured charophytes of the genus ''Chara (alga), Chara''. The bird species that populated Lake Cahuilla resembled these around the present-day Salton Sea and may have contained species from the Gulf of California as well. They include ''Aechmophorus'' grebes, American coot, American white pelican, ''Anas'' and ''Aythya'' ducks, black-crowned night heron, eared grebes, pied-billed grebes and most likely shorebirds. Fish species that have been identified as having lived in Lake Cahuilla include ''Catostomus latipinnis'', ''Cyprinodon macularius'', ''Elops affinis'', ''Gila elegans'', ''Gila cypha'', ''Gila robusta'', ''

'', ''Poeciliopsis occidentalis'', ''Ptychocheilus lucius'', and ''Xyrauchen texanus''. Lake Cahuilla featured similar fish species as the lower Colorado River. Diatom species identified in sediments left by Lake Cahuilla include ''Cocconeis placentula'', ''Epithermia argus'', ''Epithermia turgida'', ''Mastogloia elliptica'', ''Navicula palpebralis'', ''Pinnularia viridis'', ''Rhopalodia gibba'', ''Surirella striatula'', ''Terpsinoe musica'' and ''Tetracyclus lacustris''. Other species whose identification is less clear are ''Campylodiscus clypeus'', ''Cyclotella kuetzingiana'', ''Hantzschia taenia'', ''Navicula clementis'', ''Navicula ergadensis'', ''Nitzschia etchegoinia'', ''Nitzschia granulata'' and ''Synedra ulna''. During periods when the level in the lake rose, vegetation in the flooded areas drowned and the organic material coming from it was washed ashore and later buried in coastal sediments. Five fish species and waterfowl populated the lake, and evidence exists of marshes on its shore. The flora and fauna along the seashores was probably robust enough to tolerate lake level drops for a while before increased salinity resulted in their disappearance.

History

Chronology

The history of Lake Cahuilla spans the late

and the

, with maximum lake extents occurring starting from 40,000 years ago. Pleistocene shorelines are found mainly on the western side at altitudes of ; an early high shoreline was dated at 37,400 ± 2,000 years before present. At Travertine Point, evidence of a lake going back to 13,000 ± 200 years ago has been found. According to dates obtained from tufas, between 20,350 and 1,300 years before present water levels were always more than above sea level. In the northeastern section of the lake, Pleistocene shorelines lie close to the path of the Coachella Canal. Pleistocene water levels are generally higher than the Holocene ones which did not exceed above sea level, probably due to erosion in the Colorado River delta. The latest highstand of Cahuilla was 400–550 years before present. Water levels of above sea level occurred between 200 BC and 1580. The well preserved shorelines, lack of desert pavements and desert varnish on shore features, and a relative lack of soil and archeological evidence suggest that Lake Cahuilla reached its maximum in the late Holocene. It was assumed at first that the lake existed in a single long interval between 1000 and 1500; however, later a succession of wet and dry phases was determined from radiocarbon dating. Each phase was stable for prolonged times. Most commonly, the occurrence of five separate lake stages and six highstands is assumed. One theory assumes four highstands between 695 and 1580. One chronology assumes these highstands occurred 100 BC – 600 AD, 900–1250 and 1300–1500. Six or five different cycles are documented in

* Coachell ...

. At Superstition Hills five lake cycles from 817 to 964, 1290–1330, 1440–1640, 1480–1660, 1638–1689 and 1675–1687 are documented; the 1440–1640 cycle may have consisted of four sub-cycles that occurred within short time distances from each other or may be part of a cycle centered at 1577 ± 67. An older highstand was observed at East Mesa and dated to 3,850 years before present. At least 12 different cycles of lake growth and lake shrinkage occurred over the last 2,000 – 3,000 years. Radiocarbon dates of the highstands range 300 ± 100 to 1,580 ± 200 before present. A recent theory envisages several lake cycles at 1731-1733 AD (Lake A), 1618-1636 AD (Lake B), 1486-1503 AD (Lake C), 1118-1165 or 1192-1241 AD (Lake D), 1007-1070 AD (Lake E), 930-966 AD (Lake F), and 612 AD-5 BC (Lake G). The basin was probably not entirely dry between the last three highstands. Some legends of the Kumeyaay, Kami and

Cahuilla The Cahuilla , also known as ʔívil̃uqaletem or Ivilyuqaletem, are a Native American people of the various tribes of the Cahuilla Nation, living in the inland areas of southern California. The occurrence of a highstand ("Lake A") around 1726 ± CE is secure. It is not clear whether Lake Cahuilla was full in 1540, year in which the Coronado expedition went through the area, although some transverses in the reports about the Coronado expedition have been interpreted as to imply that it was not. It is possible that at that time, the Colorado River was draining into both the Gulf of California and Lake Cahuilla. Juan de Oñate in 1605 and Eusebio Kino in 1702 report that natives told them of the existence of a lake. Likewise a map by John Rocque 1762 shows the Colorado River draining into a lake. Williams Blake in 1853 reported of a Cahuilla legend that had a lake extending "from mountain to mountain" and evaporating "little by little", interrupted by a flood without warning. Based on observations made by Juan Bautista de Anza during his 1774 trip through the region, Lake Cahuilla did not exist by that point. It is still possible that a short refilling occurred between 1680 and 1825. Some anomalously old radiocarbon dates of Lake Cahuilla deposits may be the consequence of the Colorado River transporting ancient carbonates into the lake. In addition, discrepancies between shell and other organic material ages can reach 400–800 years owing to old carbon; shells can also absorb carbon-14 from the air. Other research has documented no substantial old carbon effects. It is likely that ephemeral lakes formed in the Lake Cahuilla basin during floods of the Colorado River, such as in 1828, 1840, 1849, 1852, 1862, 1867, and 1891. In 1873, Joseph Widney proposed to recreate the whole sea in the hope of increasing precipitation over southern California and thus to enhance agricultural productivity; this was known as the "Widney Sea". Since 1905–1907, a new lake exists where Lake Cahuilla once stood, the Salton Sea. This lake formed when heavier than average spring melt runoff in the Colorado River breached an irrigation canal. The Salton Sea might have grown to the size of Lake Cahuilla if human efforts had not stopped the flood.

Research history

In 1853,

William Phipps Blake William Phipps Blake (June 1, 1826 – May 22, 1910) was an American geologist, mining consultant, and educator. Among his best known contributions include being the first college trained chemist to work full-time for a United States chemical ...

suggested that the Colorado River Delta cut off the basin from the sea and formed a Sink (geography), playa; later two freshwater stages and one marine stage were identified in the basin. One year later he reported the existence of the shoreline. Sykes in 1914 postulated that between 1706 and 1760 the Colorado River flooded the Lake Cahuilla basin, but there is no historical evidence for this. E.E.Free in 1914, estimated the existence of only one lake cycle, on the basis of a wavecut terrace. Hubbs and Miller (1948) assumed two freshwater stages. Originally it was believed that Lake Cahuilla formed around 900 AD and existed until 1500 but with fluctuations as the Colorado River changed its course. In 1978, Philip J. Wilke proposed that two highstands occurred, one between 900 and 1250 and another between 1300 and 1500. Another proposal by Waters in 1983 suggested highstands 700–900, 940–1210 and after 1250, the latter with some brief recessions to lower lake levels. Both proposals were criticized on the grounds that they came to definite conclusions with insufficient information. Malcolm J. Rogers suggested that early highstands of Lake Cahuilla had strong effects on the spread of ceramics in the region of California and Baja California, though this is considered untenable today.

Products and significance

The

, which border old Cahuilla shorelines, were formed by sand blown from Lake Cahuilla. This theory was first formulated in 1923. The process occurred either immediately after the lake reached modern highstands, or during earlier higher stands. Most likely, sand was transported to the dune field during times where the lake receded and its bed was exposed to wind. Various stages of Lake Cahuilla may correspond to waves of migrating dunes. At first the Whitewater River and local Arroyo (creek), washes were considered the primary source of these sands, which would have been transported to the Algodones area by longshore drift. This would imply a minimum age of 160,000 years. Later the Colorado River was identified as the main source of these sediments, but still potentially with some contribution from local drainages. At prevailing winds, most of the sediments from the Colorado would have been transported to the Cerro Prieto area and possibly carried by wind to the Gran Desierto de Altar. Clay and fine silt, dominated by lutite, were deposited in the lake. Closer to the shore, sand was also emplaced. River delta, Deltaic deposits have been found as well. Minerals identified include biotite, chlorite, illite, kaolinite, montmorillonite and muscovite, with varying colors depending on the origin of the sediments. The material deposited by Lake Cahuilla is also known as the Cahuilla formation (geology), formation. The Borrego and Pleistocene Brawley formations may also be linked to Lake Cahuilla. These lacustrine materials bury the northern part of the Colorado River Delta, and they give the ground a grayish color. The clays left by the lake were used for the production of ceramic by the inhabitants of the region; likewise Lake Cahuilla is responsible for the fertile soils of the Coachella Valley and Imperial Valley, an important agricultural province of the United States. Halite deposits left by the lake were mined in the 19–20th century. The weight of the water in Lake Cahuilla caused the surface beneath the lake to sink by about . Such ground depression has been observed at the ancient lakes Lake Bonneville, Lake Lahontan, Lake Minchin, and the modern reservoirs of Lake Mead, Three Gorges Reservoir in China, and La Grande River, La Grande in Quebec. The genus ''Cahuillus'' of Helminthoglyptidae, helminthoglyptid land snails is named after the lake. It contains the species ''Cahuillus indioensis'' with two subspecies ''indioensis'' and ''cathedralis'', ''Cahuillus greggi'' and ''Cahuillus mexicanus''.

Archaeology

Numerous archeological sites of the

Cahuilla The Cahuilla , also known as ʔívil̃uqaletem or Ivilyuqaletem, are a Native American people of the various tribes of the Cahuilla Nation, living in the inland areas of southern California.Colorado River Delta The Colorado River Delta is the region where the Colorado River flows into the Gulf of California (also known as the Sea of Cortez) in eastern Mexicali Municipality in the north of the state of Baja California in northwesternmost Mexico. The ...

which lost part of its water supply. The distribution of the languages in the region may reflect the effects of fluctuations of Lake Cahuilla; population shifts caused by the drying and flooding of Lake Cahuilla may have favored exchanges between the Tepiman and River Yuman languages and the propagation of Haplogroup B (mtDNA), B2a mitochondrial haplogroups in the native people. When Lake Cahuilla filled, it may have encouraged Quechan people to migrate to the area. This migration is considered to be a possible source for the spread of agriculture to the Peninsular Ranges. When Lake Cahuilla dried out after 1500 AD, these people would have migrated back south and west, a move possibly recorded in the oral traditions of the Quechan people and of people they mixed with. Legends have it that Lost Ship of the Desert, lost ships, sometimes described as pirate ships or galleons, sailed Lake Cahuilla and are now buried somewhere in the Colorado Desert.

References

Sources

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External links

* * * * * * {{authority control Lakes of the Great Basin, Cahuilla Former lakes of the United States, Cahuilla Pleistocene Colorado River Imperial Valley Coachella Valley Lower Colorado River Valley Geography of the Colorado Desert Geology of California Lakes of California, Cahuilla Natural history of Riverside County, California