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The Salton Sea is a shallow, saline, endorheic rift lake located directly on the San Andreas Fault, predominantly in 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 〔http://waterdata.usgs.gov/ca/nwis/uv?site_no=10254005〕 below sea level. The deepest point of the sea is 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 soil (creating fertile farmland) and building up the terrain constantly changing the course of the river. For the next thousands of years the river has 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 itself many times. The latest natural cycle occurred around 1600-1700 as remembered by Native Americans who talked with the first settlers. Fish traps still exist at many locations and it is evident that the Native Americans would move the traps depending upon the cycle. The most recent inflow of water from the now heavily controlled Colorado River was accidentally created by the engineers of the California Development Company in 1905. In an effort to increase water flow into the area for farming, irrigation canals were dug from the Colorado River into the valley. Due to fears of silt buildup, a cut was made in the bank of the Colorado River to further increase the water flow. The resulting outflow overwhelmed the engineered canal, and the river flowed into the Salton Basin for two years, filling the historic dry lake bed and creating the modern sea, before repairs were completed. While it varies in dimensions and area with fluctuations in agricultural runoff and rainfall, the Salton Sea averages by . With an estimated surface area of or , the Salton Sea is the largest lake in California. The average annual inflow is less than , which is enough to maintain a maximum depth of and a total volume of about . However, due to changes in water apportionments agreed upon for the Colorado River under the Quantification Settlement Agreement of 2003, the overall water level of the Sea is expected to decrease significantly between 2013 and 2021. The lake's salinity, about , is greater than that of the waters of the Pacific Ocean (), but less than that of the Great Salt Lake (which ranges from ). The concentration increases by about one percent every year. About of salt is deposited in the valley each year. ==History== 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 had reached the western shore of the Gulf of California, creating a massive barrier that excluded 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, including most of the area occupied by Anza-Borrego Desert State Park, would all be submerged, as the Gulf would extend as far north as Indio. As a result, the Salton Basin has over the ages been alternately a freshwater lake, an increasingly saline 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 was replenished by the rivers and rainfall, a cycle that repeated itself many times over hundreds of thousands of years, perhaps cycling every 400 to 500 years.〔 Some evidence indicates the basin was occupied periodically by multiple lakes. Wave-cut shorelines at various elevations are still preserved on the hillsides of the east and west margins of the present lake, the Salton Sea, showing 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. Once part of a vast inland sea that covered a large area of Southern California, the endorheic Salton Sink was the site of a major salt mining operation.〔(The Salton Sea – Its Beginnings ). Accessed 2010-06-14〕 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.〔(Carpelan, Lars H. History of the Salton Sea )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Salton Sea」の詳細全文を読む スポンサード リンク
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