Shallow saline lake in southern California

Map of the Salton Sea drainage area

The Salton Sea is a shallow, saline, endorheic rift lake on the San Andreas Fault, predominantly in the U.S. state of California's Imperial and Coachella valleys.

The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Imperial and Riverside counties in Southern California. Its surface is 236.0 ft (71.9 m) below sea level as of January 2018.[1] Its deepest point is 5 ft (1.5 m) higher than the lowest point of Death Valley. The sea is fed by the New, Whitewater, and Alamo rivers, as well as agricultural runoff, drainage systems, and creeks.

Over millions of years, the Colorado River has flowed into the Imperial Valley and deposited alluvium (soil) creating fertile farmland, building up the terrain and constantly moving its main (or only) river delta. For thousands of years, the river has alternately flowed into and out of the valley, alternately creating a freshwater lake, an increasingly saline lake, and a dry desert basin, depending on river flows and the balance between inflow and evaporative loss. The cycle of filling has been about every 400–500 years and has repeated many times.

One such most notable instance took place around 700 AD – great flows of water into the basin, creating Lake Cahuilla, which at its peak was 115 miles (185 km) long, 35 miles (56 km) wide, and 314 feet (96 m) deep, making it one of the largest lakes in North America. This watering of the basin, during extended severe drought, benefited hunter-gatherers who lived there: although the water was too saline to drink, its presence attracted fish and waterfowl to the area.[2] The lake existed for over 600 years until the intake silted up, leaving a closed basin that dried up in around 50 years.

The latest natural cycle occurred around 1600–1700 AD, according to Native Americans who spoke with the first European settlers. Fish traps still exist at many locations, and the Native Americans evidently moved the traps depending upon the cycle.

The inflow of water from the now heavily controlled Colorado River was accidentally created by the engineers of the California Development Company in 1905. To provide water to the Imperial Valley for farming, beginning in 1900, an irrigation canal was dug from the Colorado River to the old Alamo River channel, directing the water west and then north near Mexicali. The headgates and canals suffered silt buildup, so a series of cuts were made in the bank of the Colorado River to further increase the water flow. The resulting outflow overwhelmed the third intake, "Mexican Cut", near Yuma, Arizona, and the river flowed into the Salton Basin for two years, filling what was then a dry lake bed and creating the modern sea, before repairs were completed.[3][4][5]

While it varies in dimensions and area with fluctuations in agricultural runoff and rainfall, the Salton Sea is about 15 by 35 miles (24 by 56 km). With an estimated surface area of 343 square miles (890 km2) or 350 square miles (910 km2), the Salton Sea is the largest lake in California by surface area.[6][7][8] The average annual inflow is less than 1.2 million acre⋅ft (1.5 km3), which is enough to maintain a maximum depth of 43 feet (13 m) and a total volume of about 6 million acre⋅ft (7.4 km3). However, due to changes in water apportionments agreed upon for the Colorado River under the Quantification Settlement Agreement of 2003, the surface area of the sea is expected to decrease by 60% between 2013 and 2021.[9][10][needs update]

The lake's salinity, about 56 grams per litre (7.5 oz/US gal), is greater than that of the Pacific Ocean (35 g/l (4.7 oz/US gal)), but less than that of the Great Salt Lake (which ranges from 50 to 270 g/l (6.7 to 36.1 oz/US gal)). The concentration has been increasing at a rate of about 3% per year.[11] About 4 million short tons (3.6 million t) of salt are deposited in the valley each year.[12]

In 2020, Palm Springs Life magazine summarized the ecological situation as "Salton Sea derives its fame as the biggest environmental disaster in California history".[13]

History [ edit ]

The area was once part of a vast inland sea that covered a large area of Southern California. Geologists estimate that for three million years, at least through all the years of the Pleistocene glacial age, a large delta was deposited by the Colorado River in the southern region of the Imperial Valley. Eventually, the delta reached the western shore of the Gulf of California, creating a barrier that separated the area of the Salton Sea from the northern reaches of the Gulf. Were it not for this barrier, the entire Salton Sink along with the Imperial Valley would be submerged as the Gulf would extend as far north as Indio.[14]

Since the exclusion of the ocean, the Salton Basin has over the ages been alternately a freshwater lake, an increasingly saline endorheic lake, and a dry desert basin, depending on river flows and the balance between inflow and evaporative loss. A lake exists only during times it is replenished by the rivers and rainfall, a cycle that has repeated many times over hundreds of thousands of years,[15] perhaps cycling every 400 to 500 years.[16]

Evidence that the basin was occupied periodically by multiple lakes includes wave-cut shorelines at various elevations preserved on the hillsides of the east and west margins of the present lake, the Salton Sea. These indicate that the basin was occupied intermittently as recently as a few hundred years ago. The last of the Pleistocene lakes to occupy the basin was Lake Cahuilla, also periodically identified on older maps as Lake LeConte or the Blake Sea, after American professor and geologist William Phipps Blake.

Throughout the Spanish period of California's history, the area was referred to as the "Colorado Desert" after the Colorado River. In a railroad survey completed in 1855, it was called "the Valley of the Ancient Lake". On several old maps from the Library of Congress, it has been found labeled "Cahuilla Valley" (after the local Native American tribe) and "Cabazon Valley" (after a local Native American chief – Chief Cabazon). "Salt Creek" first appeared on a map in 1867 and "Salton Station" is on a railroad map from 1900, although this place had been there as a rail stop since the late 1870s.[17] Until the advent of the modern sea, the Salton Sink was the site of a major salt-mining operation.[18]

History during the 1900s [ edit ]

Original caption: "Dry Bed of Colorado River Below Imperial Intake ... River Diverted Into Imperial Canal

In 1900, the California Development Company began construction of irrigation canals to divert water from the Colorado River into the Salton Sink, a dry lake bed. After construction of these irrigation canals, the Salton Sink became fertile for a time, allowing farmers to plant crops.[19]

Within two years, the Imperial Canal became filled with silt from the Colorado River. Engineers tried to alleviate the blockages to no avail. In 1905, heavy rainfall and snowmelt caused the Colorado River to swell, overrunning the third intake cut into the bank of the river and sending the flood into the Alamo Canal. The resulting flood poured down the canal, and down two former dry arroyos: the New River in the west, and the Alamo River in the east, each about 60 mi (97 km) long.[20] Over about two years, these two newly created rivers [21] carried the entire volume of the Colorado River into the Salton Sink.[16]

The Southern Pacific Railroad tried to stop the flooding by dumping earth into the canal's headgates area, but the effort was not fast enough, and the river eroded deeper and deeper into the dry desert sand of the Imperial Valley. A large waterfall formed as a result and began cutting rapidly upstream along the path of the Alamo Canal that now was occupied by the Colorado. This waterfall was initially 15 feet (4.6 m) high, but grew to 80 feet (24 m) high before the flow through the breach was stopped. Originally, it was feared that the waterfall would recede upstream to the true main path of the Colorado, becoming up to 100 to 300 feet (30 to 91 m) high, at which point it would be practically impossible to fix the problem.

Salton Sea

As the basin filled, the town of Salton, a Southern Pacific Railroad siding, and Torres-Martinez Native American land were submerged. The sudden influx of water and the lack of any drainage from the basin resulted in the formation of the Salton Sea.[22][23]

The U.S. Navy conducted a preliminary inspection of the Salton Sea in January 1940, and the Salton Sea Test Base (SSTB, run by Sandia Labs) was initially commissioned as the Salton Sea Naval Auxiliary Air Station, in October 1942. The SSTB, just to the southeast of Salton City, originally functioned as an operational and training base for seaplanes. Additional activities at the base included experimental testing of solid-fuel plane-launched rockets, jet-assist take-off testing, aeroballistic testing of inert atomic weapon test units at land and marine target areas, training bombing at marine targets, testing of the effects of long-term storage on atomic weapons, testing of the Project Mercury space capsule parachute landing systems, parachute training and testing, and military training exercises. The base was abandoned in 1978.[24]

The continuing intermittent flooding of the Imperial Valley from the Colorado River led to the idea of the need for a desilting dam on the Colorado River for flood control. The Imperial Dam was built to avoid the flooding that created the Salton Sea.[25]

Subsequent evolution [ edit ]

The Salton Sea had some success as a resort area, with Salton City, Salton Sea Beach, and Desert Shores, on the western shore and Desert Beach, North Shore, and Bombay Beach, built on the eastern shore in the 1950s. However, many of the settlements substantially shrank in size, or have been abandoned, mostly due to the increasing salinity and pollution of the lake over the years from agricultural runoff and other sources. Many of the species of fish that lived in the sea have been killed off by the combination of pollutants, salt levels, and algal blooms. Dead fish have been known to wash up in mass quantities on the beaches. The smell of the lake, combined with the stench of the decaying fish, also contributed to the decline of the tourist industry around the Salton Sea. The US Geological Survey describes the smell as "objectionable", "noxious", "unique", and "pervasive".[26]

An article in June 2018 stated that as "California’s largest lake dries up, it threatens nearby communities with clouds of toxic dust", increasing the incidence of asthma among the population. The coverage added that "the air in Imperial County is some of the worst in the country, a dense blend of ozone and particulate matter".[27] An April 2020 news item stated that in the Eastern Coachella, communities were facing "disproportionately higher rates of asthma and respiratory complications" because of high concentrations of contaminants in the air".[28]

Some people are visiting the Salton Sea and the surrounding settlements to explore the abandoned structures and see the squatter settlement of Slab City. The town of Niland is 1.5 miles (2.4 km) southeast of the sea, with a population of 1,006. A visitor to the community in 2018 found "quirky decorations, graffiti, and some questionable structural integrity" but also "establishments like motels, RV parks, laundromats, and a diner".[29] In late June 2020, a fire in Niland caused a great deal of damage in Niland, displacing 112 people; by that time, the estimated population had diminished to 500.[30]

Smithsonian magazine in October 2018 referred to Slab City as a "Squatters’ Paradise" which locals consider to be "one of America's last free places".[31] The article said of the population: "There are clearly people there who don’t want to be found, so there’s something about disappearing, and the desert offers that kind of opportunity".[32]

The population of Bombay Beach declined for years and the buildings were rotting away, but some people had moved into the settlement. A news item in April 2018 stated that it was "enjoying a rebirth of sorts with an influx of artists, intellectuals and hipsters who have turned it into a bohemian playground".[33] The population estimate for 2020 was 415 persons, certainly higher than the official census number of 295 in 2010.[34]

A 2020 article provided this comment about the settlements around the Salton Sea:[35]

Since 2011, Bombay Beach and its surrounds have been reinvented as a destination for desert art. It’s not alone in that distinction – south of the city lie the towns of Niland and Slab City, other areas that have attracted artists and led to creations like East Jesus and Salvation Mountain.

A visitor in 2019 wrote that in Bombay Beach, there were many "discarded homes and trailers long-since abandoned ... windowless husks blanketed in graffiti, surrounded by broken furniture and rubble.[36]

Climate [ edit ]

According to the Köppen climate classification system, the Salton Sea has a Hot desert climate (BWh). According to the United States Department of Agriculture, the Plant Hardiness zone is 9b with an average annual extreme minimum temperature of 28.5 °F (−1.9 °C).[37] The temperature of the surface water changes with the seasonally varying air temperature. Winter surface water can reach temperatures as low as 50 °F (10 °C) and summer surface water highs can reach 95 °F (35 °C).[38]

Climate data for Salton Sea, Imperial County, CA Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Average high °F (°C) 70.9

(21.6) 74.5

(23.6) 80.3

(26.8) 86.8

(30.4) 95.0

(35.0) 102.9

(39.4) 107.2

(41.8) 106.6

(41.4) 102.0

(38.9) 91.5

(33.1) 79.0

(26.1) 69.8

(21.0) 88.9

(31.6) Average low °F (°C) 41.7

(5.4) 45.0

(7.2) 50.1

(10.1) 55.3

(12.9) 62.4

(16.9) 69.2

(20.7) 76.7

(24.8) 77.7

(25.4) 71.3

(21.8) 59.9

(15.5) 48.5

(9.2) 40.9

(4.9) 58.3

(14.6) Average precipitation inches (mm) 0.38

(9.7) 0.43

(11) 0.40

(10) 0.06

(1.5) 0.02

(0.51) 0.02

(0.51) 0.09

(2.3) 0.22

(5.6) 0.20

(5.1) 0.21

(5.3) 0.15

(3.8) 0.38

(9.7) 2.56

(65) Average relative humidity (%) 39.6 37.8 33.7 28.6 27.3 24.5 29.6 32.2 30.6 30.7 34.6 38.9 32.3 Average dew point °F (°C) 32.0

(0.0) 33.9

(1.1) 35.9

(2.2) 36.9

(2.7) 42.2

(5.7) 45.6

(7.6) 55.8

(13.2) 58.3

(14.6) 52.1

(11.2) 42.7

(5.9) 35.3

(1.8) 30.8

(−0.7) 41.8

(5.4) Source: PRISM Climate Group[39]

Ecology [ edit ]

Dead fish on the western shore of Salton City

Potential natural vegetation [ edit ]

According to the A. W. Kuchler U.S. Potential natural vegetation Types, the area roughly within 3 miles (4.8 km) of the sandy shoreline of the Salton Sea would have a Saltbush / Greasewood (40) vegetation type and a Great Basin Shrubland (7) vegetation form.[40]

Fish population [ edit ]

Due to the high salinity, very few fish species can tolerate living in the Salton Sea. Introduced tilapia (hybrid Mozambique × Wami) are the main fish that can tolerate the high salinity levels and pollution.[41][42] As of 2014, other fresh and brackish water fish species lived in the rivers and canals that fed the Salton Sea, including redbelly tilapia, threadfin shad, carp, red shiner, channel catfish, white catfish, largemouth bass, mosquitofish, sailfin molly, and the vulnerable desert pupfish.[42][43]

The California Office of Environmental Health Hazard Assessment developed a safe eating advisory for fish caught in the Salton Sea based on levels of mercury or PCBs found in local species.[44]

A September 2019 report stated that ten years earlier, "there were some 100 million fish in the Sea. Now, more than 97 percent of those fish are gone".[45]

Avian population [ edit ]

The Salton Sea has been termed a "crown jewel of avian biodiversity" by Dr. Milt Friend of the Salton Sea Science Office. Over 400 species have been documented at the Salton Sea. The most diverse and probably the most significant populations of bird life in the continental United States are hosted, rivaled only by Big Bend National Park in Texas.[46] It supports 30% of the remaining population of the American white pelican.[47] The Salton Sea is also a major resting stop on the Pacific Flyway. On 18 November 2006, a Ross's gull, a high Arctic bird, was sighted and photographed there.[48]

A December 2018 report by the National Georgraphic Society stated that the Sea is an important stopover point for migrating birds. "Nearly all of California’s population of eared grebes, for example, stop over at the lake, and at least a third of all the white pelicans living in North America ..." The report expressed concern about the reducing input of water into the Sea and the increasing salinity. "Without that extra water, the lake’s shrinking will start to accelerate—making it saltier, smaller, less welcoming to the birds that rely on it during migration".[49]

Increasing salinity [ edit ]

Salt deposits along the eastern shore of the sea

The lack of an outflow means the Salton Sea does not have a natural stabilization system; it is very dynamic. Fluctuations in the water level caused by variations in agricultural runoff, the ancient salt deposits in the lake bed, and the relatively high salinity of the inflow feeding the sea are all causing increasing salinity. The body was initially a freshwater lake, but by the 1960s, its rising salinity had begun to jeopardize some of its species.[50] With a salinity now exceeding 5.0% w/v (saltier than seawater), most species of fish can no longer survive. A freshwater fish notable for its ability to withstand the rising salinity of the Salton Sea, the desert pupfish, can survive salinities ranging from 0.0% to 7.0%.[51] Fertilizer runoffs have resulted in eutrophication, with large algal blooms and elevated bacterial levels.[52] Both the hypersalinity and presence of contaminants in the Salton Sea triggered massive die-offs in the fish and avian populations; Salt water carries less oxygen than fresh water, which was further depleted by algal blooms and by extreme temperatures during the summer period, and the contamination promoted the outbreak and spread of diseases such as avian cholera. In turn, the loss of several species of fish that the avian population depended on for food increased their risk of starvation, exacerbating their decline.

By the 1970s, the runoff which was full of salty chemicals led to a warning that the salinity of the lake would no longer sustain wildlife; that occurred by the early 1980s.[53]

In November 2019, an emergency was declared because of the "heavily polluted New River, which empties into the Salton Sea". Some were hoping that this would help to accelerate a restoration project which would enable the state to obtain federal funding. By January 2020, the salinity of the Salton Sea was double that of the Atlantic Ocean.[54] An undated report on the Imperial County web site provided these specifics: "Salton Sea salinity is about 44,000 mg/L, that is approximately 4.4% salt. The amount of salts that is deposited in the Imperial Valley agricultural land with irrigation water is approximately four million tons of salts annually. To maintain crop productivities, equal amount of salts must be leached from the root zone".[55]

Geology [ edit ]

Earthquakes and tectonic setting [ edit ]

Aerial view of the Salton Sea from the north

Aerial view of the Salton Sea from the south

The Salton Sea and surrounding basin sits over the San Andreas Fault, San Jacinto Fault, Imperial Fault Zone, and a "stepover fault" shear zone system. Geologists have determined that previous flooding episodes from the Colorado River have been linked to earthquakes along the San Andreas Fault. Sonar and other instruments were used to map the Salton Sea's underwater faults during the study. During the period when the basin was filled by Lake Cahuilla, a much larger inland sea, earthquakes higher than magnitude 7 occurred roughly every 180 years, the last one occurring within decades of 1700. Computer models suggest the normal faults in the area are most vulnerable to deviatoric stress loading by filling in of water. Currently, a risk still exists for an earthquake of magnitude 7 to 8. Simulations also showed, in the Los Angeles area, shaking and thus damage would be more severe for a San Andreas earthquake that propagated along the fault from the south, rather than from the north. Such an earthquake also raises the risk for soil liquefaction in the Imperial Valley region.[56][57]

The effective drainage divide that separates the Salton Sea from the Gulf of California is about 9 m (30 ft) in elevation and is located near Delta, northeastern Baja California State, Mexico, south-southeast of Mexicali.[58] Past sea level rise may partially be responsible for the salinity of the lake, while potential future changes in sea levels could occur. However, other factors such as hydrothermal vents, diffusion of salt from minerals and sediment, including concentrated brine, and evaporites are another contributor to salinity, as is the recent lowering of lake levels raising the salinity, though sedimentary records show the lake surface elevation reached levels 10–12 m above world sea level in the 1500s.[59]

Volcanism [ edit ]

Evidence of geothermal activity is also visible. The Salton Buttes are volcanoes in the geothermal field of the same name. Mudpots and mud volcanoes are found on the eastern side of the Salton Sea.[60] The area is used for geothermal electricity generation, with plants located along the southeastern shore of the Salton Sea in Imperial County.[61]

Remediation efforts [ edit ]

Early efforts and proposals for a sea level canal [ edit ]

Alternatives for "saving" the Salton Sea have been evaluated since 1955.[citation needed]

Interest in the sea was sparked in the 1990s by Congressman Sonny Bono.[62] His widow, Mary Bono Mack, elected to fill his seat, has continued to be interested in the Salton Sea, as has Representative Jerry Lewis of Redlands.[62] In 1998, the Sonny Bono Salton Sea Restoration Project was named for the politician.[62]

In the late 1990s, the Salton Sea Authority, a local joint powers agency, and the US Bureau of Reclamation began efforts to evaluate and develop an alternative to save the Salton Sea. A draft Environmental Impact Report/Environmental Impact Statement, which did not specify a preferred alternative, was released for public review in 2000. Since that time, the Salton Sea Authority has developed a preferred concept[63][full citation needed] that involves the construction of a large dam that would impound water to create a marine sea in the northern and southern parts of the sea and along the western edge.[citation needed]

Satellite image of the Salton Sea with surrounding developments

Many other concepts have been proposed.[64] Aqua Genesis Ltd propose to bring in seawater from the Gulf of California, rapidly desalinate it at Salton Sea tapping into geothermal heat, then sell the non-saline water. This concept would involve the construction of over 20 miles (32 km) of pipes and tunneling; amid increasing water demand, it would provide 1,000,000 acre feet (1.2 km3) of water to Southern California coastal cities each year.[65] One vying project as to the sea salt market is to pipe seawater to a wetland in Mexico, Laguna Salada for that trade.

State restoration plan [ edit ]

Abandoned, salt-encrusted structures on the Salton Sea shore at Bombay Beach

In 2003, the Imperial Irrigation District agreed to sell a portion of its allotment from the Colorado River for 45 years to the San Diego County Water Authority.[66] The California State Legislature, by legislation enacted in 2003 and 2004, directed the Secretary of the California Resources Agency to prepare a restoration plan for the Salton Sea ecosystem, and an accompanying Environmental Impact Report.[67] As part of this effort, the Secretary for Resources has established an advisory committee to provide recommendations to assist in the preparation of the Ecosystem Restoration Plan, including consultation throughout all stages of the alternative selection. The California Department of Water Resources and California Department of Fish and Game are leading the effort to develop a preferred alternative for the restoration of the Salton Sea ecosystem and the protection of wildlife dependent on that ecosystem.

On January 24, 2008, the California Legislative Analyst's Office released a report titled "Restoring the Salton Sea."[67] The preferred alternative outlined in the draft plan calls for spending almost $9 billion over 25 years and proposes a smaller but more manageable Salton Sea. The amount of water available for use by humans and wildlife would be reduced by 60% from 365 square miles (950 km2) to about 147 square miles (380 km2). About 52 miles (84 km) of barrier and perimeter dikes – constructed most likely out of boulders, gravel, and stone columns – would be erected, along with earthen berms to corral the water into a horseshoe shape along the northern shoreline of the sea from San Felipe Creek on the west shore to Bombay Beach on the east shore. The central portion of the sea would be allowed to evaporate almost completely and would serve as a brine sink, while the southern portion of the sea would be constructed into a saline habitat complex. Construction on the project would be completed by 2035.

By 2014, large swaths of lake bed were exposed and salt levels drastically increased due to mandated water transfers to metropolitan areas along the coast and other factors, limiting the water inflow. Besides the resulting fish kills, the shrinking lake interrupts the bird migration, causes dust clouds, and negatively impacts local tourism.[68] During the first 15 years after the sale of the Imperial water to San Diego County, the irrigation district has been required to put water into the Salton Sea to compensate for the loss of agricultural runoff needed to replenish the sea. Since the requirement expired in 2017, the district sent a letter to the California State Water Resources Control Board in 2014 asking that the board sponsor negotiations to get the state to fulfill its obligation to stop the deterioration of the sea. Pacific Institute, an Oakland-based environmental think tank, was warning that the lack of replenishment water was leading to a "period of very rapid deterioration."[69] The rapidly shrinking sea was a "looming environmental and public health crisis"[66] With the increased shrinkage, dust storms would increase and a rotten-egg smell could reach to the coastal cities.[69]

In 2018, California's Natural Resources Agency received 11 proposals to increase waterflow to the sea in order to reduce dust and dust-borne toxins. Proposal costs ranged from $300 million to several billion dollars. No winner was selected in this phase.[70] In February 2020, the agency finished the "Bruchard Road Dust Suppression Project" and reported further actions to be taken until 2028.[71]

A July 2020 news item (written by a lobby group) discussed one method to improve the Sea "to prevent wind spreading toxic dust": refilling it with water imported from the Sea of Cortés; that would require the building of an aqueduct. (A June 9 research report however stated that the cost of "transferring water from agricultural users to the Salton Sea" would be lower and achievable using existing infrastructure).[72] The aqueduct proposal, and others, hang on the outcome of a feasibility study expected in late 2021.[73]

In popular culture [ edit ]

An abandoned boat stuck in the ground, close to the west coast marina of the Salton Sea

Films [ edit ]

Games [ edit ]

In the video-game Grand Theft Auto V (2013), a location called the Alamo Sea is based on the Salton Sea; Sandy Shores, a town that sits on the lake's southern edge, is based on the town of Desert Shores.[86]

Music [ edit ]

Television [ edit ]

The History Channel's 2006 episode "Engineering Disasters 18" (#13-04), from the television documentary series Modern Marvels , describes the combined manmade and natural events leading to the creation of the Salton Sea in the early 20th century, its brief popularity as a resort destination midcentury, and its subsequent decline due to high salinity and farm runoff. Impacts to Salton Sea fish and bird populations are addressed and future plans to rescue the sea are described. [88]

, describes the combined manmade and natural events leading to the creation of the Salton Sea in the early 20th century, its brief popularity as a resort destination midcentury, and its subsequent decline due to high salinity and farm runoff. Impacts to Salton Sea fish and bird populations are addressed and future plans to rescue the sea are described. National Geographic Explorer was present on June 10, 2018 to record an encounter between supporters of a flat Earth and members of the Independent Investigations Group. An experiment successfully demonstrated the curvature of the earth via the disappearance over distance of boat-based and shore-based targets.[89]

See also [ edit ]

References [ edit ]