Los Angeles Basin
Encyclopedia
The Los Angeles Basin is the coastal sediment
-filled plain located between the Peninsular
and Transverse ranges
in southern California
in the United States
containing the central part of the city of Los Angeles
as well as its southern and southeastern suburbs (both in Los Angeles
and Orange
counties). It is approximately 35 miles (56 km) long and 15 miles (24 km) wide, bounded on the north by the Santa Monica Mountains
and Puente Hills
, and on the east and south by the Santa Ana Mountains
and San Joaquin Hills
. The Palos Verdes Peninsula, formerly an island, marks the outer edge of the basin along the coast. The confluence of the Los Angeles and Rio Hondo rivers is the center of the basin.'
approximately 15 million years ago (mya), when the terrain was underwater, during a crustal upheaval caused by a clockwise shift in the surrounding mountains. The underlying crustal weakening resulted in the formation of the large bowl of the basin. Sediment from the sea and rivers accumulated in the undersea bowl, building up in thick layers.
Approximately 5 million years ago, the crustal stretching subsided and the ocean floor of the basin was forced to the surface. Additional sediment accumulated during the upswell resulting in the floor of the basin as it exists today.
, that were once under the basin but have been largely extracted.
Other large active oil fields include the Huntington Beach Oil Field
, which underlies much of the city of Huntington Beach; and the Torrance Oil Field, adjacent to the Wilmington field on the northwest. Most of the numerous fields in the basin have either been abandoned or greatly scaled back in production since the early part of the 20th century; in the 1890s the oil field directly north of downtown Los Angeles, the Los Angeles City Oil Field
, led the state of California
in oil production. Some of the oil fields even in the dense urban core remain productive, including the Beverly Hills Oil Field
.
was recovered commercially from brine co-produced with oil. Dow Chemical Company
operated a number of plants at oil fields in the Los Angeles Basin, and recovered iodine from brines that averaged 50 parts per million iodine. Production started in 1932 and lasted into the 1960s.
s. The basin is often compared by geologist
s to a "a bowl of jelly" that can shake violently when driven by seismic
activity.
meters.
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
-filled plain located between the Peninsular
Peninsular Ranges
The Peninsular Ranges are a group of mountain ranges, in the Pacific Coast Ranges, which stretch from southern California in the United States to the southern tip of Mexico's Baja California peninsula; they are part of the North American Coast Ranges that run along the Pacific coast from Alaska...
and Transverse ranges
Transverse Ranges
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region that runs along the Pacific coast from Alaska to Mexico in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie between...
in southern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
containing the central part of the city of Los Angeles
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...
as well as its southern and southeastern suburbs (both in Los Angeles
Los Angeles County, California
Los Angeles County is a county in the U.S. state of California. As of 2010 U.S. Census, the county had a population of 9,818,605, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states...
and Orange
Orange County, California
Orange County is a county in the U.S. state of California. Its county seat is Santa Ana. As of the 2010 census, its population was 3,010,232, up from 2,846,293 at the 2000 census, making it the third most populous county in California, behind Los Angeles County and San Diego County...
counties). It is approximately 35 miles (56 km) long and 15 miles (24 km) wide, bounded on the north by the Santa Monica Mountains
Santa Monica Mountains
The Santa Monica Mountains are a Transverse Range in Southern California, along the coast of the Pacific Ocean in the United States.-Geography:...
and Puente Hills
Puente Hills
The Puente Hills is a chain of hills, one of the lower Transverse Ranges, in an unincorporated area in eastern Los Angeles County, California.-Geography:...
, and on the east and south by the Santa Ana Mountains
Santa Ana Mountains
The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately 36 mi southeast of the Los Angeles Basin largely along the border between Orange and Riverside counties.- Geography :The range starts in the...
and San Joaquin Hills
San Joaquin Hills
The San Joaquin Hills are a set of low hills in coastal Orange County, California. They extend in a northwest-southeast direction, starting in the northwest in Newport Beach at the southern edge of the Los Angeles Basin, and extending southeast to San Juan Capistrano.-Geography and habitats:Named...
. The Palos Verdes Peninsula, formerly an island, marks the outer edge of the basin along the coast. The confluence of the Los Angeles and Rio Hondo rivers is the center of the basin.'
Geology
The sediment in the basin is up to 6 miles (10 km) deep. The basin began to form during the NeogeneNeogene
The Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
approximately 15 million years ago (mya), when the terrain was underwater, during a crustal upheaval caused by a clockwise shift in the surrounding mountains. The underlying crustal weakening resulted in the formation of the large bowl of the basin. Sediment from the sea and rivers accumulated in the undersea bowl, building up in thick layers.
Approximately 5 million years ago, the crustal stretching subsided and the ocean floor of the basin was forced to the surface. Additional sediment accumulated during the upswell resulting in the floor of the basin as it exists today.
Petroleum
The accumulation of micro-organisms during this time is believed to be the source of the large deposits of oil, including the large Wilmington Oil FieldWilmington Oil Field
The Wilmington Oil Field is a large petroleum field in Los Angeles County in southern California in the United States in terms of cumulative oil produced. Discovered in 1932, it is the third largest oil field in the United States...
, that were once under the basin but have been largely extracted.
Other large active oil fields include the Huntington Beach Oil Field
Huntington Beach Oil Field
The Huntington Beach Oil Field is part of rich pools of oil found along the West Coast of the United States in the early 1920s stretching from Huntington Beach, California to Santa Barbara, California....
, which underlies much of the city of Huntington Beach; and the Torrance Oil Field, adjacent to the Wilmington field on the northwest. Most of the numerous fields in the basin have either been abandoned or greatly scaled back in production since the early part of the 20th century; in the 1890s the oil field directly north of downtown Los Angeles, the Los Angeles City Oil Field
Los Angeles City Oil Field
The Los Angeles City Oil Field is a large oil field north of Downtown Los Angeles. Long and narrow, it extends from immediately south of Dodger Stadium west to Vermont Avenue, encompassing an area of about four miles long by a quarter mile across...
, led the state of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
in oil production. Some of the oil fields even in the dense urban core remain productive, including the Beverly Hills Oil Field
Beverly Hills Oil Field
The Beverly Hills Oil Field is a large and currently active oil field underneath part of the city of Beverly Hills, California, USA, and portions of the adjacent city of Los Angeles...
.
Iodine
In former years iodineIodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
was recovered commercially from brine co-produced with oil. Dow Chemical Company
Dow Chemical Company
The Dow Chemical Company is a multinational corporation headquartered in Midland, Michigan, United States. As of 2007, it is the second largest chemical manufacturer in the world by revenue and as of February 2009, the third-largest chemical company in the world by market capitalization .Dow...
operated a number of plants at oil fields in the Los Angeles Basin, and recovered iodine from brines that averaged 50 parts per million iodine. Production started in 1932 and lasted into the 1960s.
Earthquakes
The sedimentary character of the basin is the principal reason why it is considered especially susceptible to excessive damage during earthquakeEarthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s. The basin is often compared by geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
s to a "a bowl of jelly" that can shake violently when driven by seismic
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
activity.
Subsidence
Its loose rock structure has also led to numerous instances of subsidence as a result of petroleum extraction, the most spectacular examples being the Baldwin HillsBaldwin Hills, Los Angeles, California
Baldwin Hills is a community and neighborhood in the South Los Angeles area of Los Angeles, within southwestern Los Angeles County, California...
meters.
See also
- Climate of the Los Angeles BasinClimate of the Los Angeles BasinThe Los Angeles Basin is noted for its moderate weather. It is characterized by a Mediterranean climate or seasonal changes in rainfall——dry summer and rainy winter——but relatively modest transitions in temperature...
- Oxnard PlainOxnard PlainThe Oxnard Plain is a large coastal plain in southwest Ventura County, California bounded by the Santa Monica Mountains, the Santa Susana Mountains, and Oak Ridge to the east, the Topatopa Mountains to the north, the Santa Clara River Valley to the northeast and the Pacific Ocean to the south and...
- San Joaquin ValleySan Joaquin ValleyThe San Joaquin Valley is the area of the Central Valley of California that lies south of the Sacramento – San Joaquin River Delta in Stockton...