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Sierran Arc
In early Triassic time, an extensive volcanic arc system called the Sierran Arc began to develop along the western margin of the North American continent. In Southern California, this volcanic arc would develop throughout the Mesozoic Era to become the geologic regions known as the Sierra Nevada Batholith, the Peninsular Ranges Batholith, (in the Peninsular Ranges), and other plutonic and volcanic centers throughout the greater Mojave Desert region. Geology These massive belts of plutonic (intrusive) and volcanic (extrusive) regional belts and isolated centers developed as plate convergence and subduction took place farther west along the western continental margin. These igneous provinces shed vast quantities of sediment both eastward into the Western Interior Seaway and westward into Pacific margin basin. At the same time, older sedimentary materials and rocks were subjected to regional metamorphism throughout much of Baja and Southern California. In the region today, granitic ...
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Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of arch ...
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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 Mexico. Before becoming a state in 1952, the area was known as the North Territory of Baja California (). It has an area of (3.57% of the land mass of Mexico) and comprises the northern half of the Baja California Peninsula, north of the 28th parallel, plus oceanic Guadalupe Island. The mainland portion of the state is bordered on the west by the Pacific Ocean; on the east by Sonora, the U.S. state of Arizona, and the Gulf of California; on the north by the U.S. state of California; and on the south by Baja California Sur. The state has an estimated population of 3,769,020 as of 2020, significantly higher than the sparsely populated Baja California Sur to the south, and similar to San Diego County, California, to its north. Over 75% of t ...
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Nevadan Orogeny
The Nevadan orogeny occurred along the western margin of North America during the Middle Jurassic to Early Cretaceous time which is approximately from 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kinds of orogenic processes occurring. During the early stages of orogenesis an "Andean type" continental magmatic arc developed due to subduction of the Farallon oceanic plate beneath the North American Plate. The latter stages of orogenesis, in contrast, saw multiple oceanic arc terranes accreted onto the western margin of North America in a "Cordilleran type" accretionary orogen. Deformation related to the accretion of these volcanic arc terranes is mostly limited to the western regions of the resulting mountain ranges ( Klamath Mountain range and Sierra Nevada) and is absent from the eastern regions. In addition, the deformation experienced in these mountain ranges is mostly due to the Nevadan orogeny and not other external events such ...
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Cenozoic Era
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configuration of continents. It is the latest of three geological eras since complex life evolved, preceded by the Mesozoic and Paleozoic. It started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor. The Cenozoic is also known as the Age of Mammals because the terrestrial animals that dominated both hemispheres were mammalsthe eutherians (placentals) in the northern hemisphere and the metatherians (marsupials, now mainly restricted to Australia) in the southern hemisphere. The extinction of many groups allowed mammals and birds to greatly diversify so that ...
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Blythe, California
Blythe is a city in eastern Riverside County, California, United States. It is in the Palo Verde Valley of the Lower Colorado River Valley region, an agricultural area and part of the Colorado Desert along the Colorado River, approximately east of Los Angeles and west of Phoenix. Blythe was named after Thomas Henry Blythe, a San Francisco financier, who established primary water rights to the Colorado River in the region in 1877. The city was incorporated on July 21, 1916. The population was 18,317 at the 2020 census. History Etymology Blythe was named after Thomas Henry Blythe, a San Francisco businessman and entrepreneur. Mr. Blythe established primary water rights to the Colorado River in the southwestern California region in 1877. The town was originally named Blythe City, by Thomas Blythe himself, but the name was shortened to simply ''Blythe'' around the time the first post office was opened in 1908. Early years In the early or mid-1870s, William Calloway (kn ...
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McCoy Mountains
The McCoy Mountains are located in southeastern California in the United States. The southeast terminus of the range lies adjacent the western edge of the Parker Valley in a southern stretch of the Lower Colorado River Valley corridor. Geography The range lies in a northwest-southeasterly direction east of the Palen Mountains and south of the Little Maria Mountains. The mountain range is approximately 18 miles long and is located just north of Interstate 10, and about seven miles northeast of Chuckawalla Valley State Prison. The mountains reach an elevation of 2,054 feet above sea level at McCoy Peak, at the southern end of the range. Downtown Blythe, California is about 10 miles to the east. Palen/McCoy Wilderness Area The McCoy Mountains are in thPalen/McCoy Wilderness Area managed by the Bureau of Land Management. Within the Palen-McCoy Wilderness are the Granite, McCoy, Palen, Little Maria, and Arica Mountains, which are five distinct mountain ranges separated by broad ...
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Santa Barbara, California
Santa Barbara ( es, Santa Bárbara, meaning "Saint Barbara") is a coastal city in Santa Barbara County, California, of which it is also the county seat. Situated on a south-facing section of coastline, the longest such section on the West Coast of the United States, the city lies between the steeply rising Santa Ynez Mountains and the Pacific Ocean. Santa Barbara's climate is often described as Mediterranean, and the city has been dubbed "The American Riviera". According to the 2020 U.S. Census, the city's population was 88,665. In addition to being a popular tourist and resort destination, the city has a diverse economy that includes a large service sector, education, technology, health care, finance, agriculture, manufacturing, and local government. In 2004, the service sector accounted for 35% of local employment. Education in particular is well represented, with four institutions of higher learning nearby: the University of California, Santa Barbara, Santa Barbara City ...
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Los Padres National Forest
Los Padres National Forest is a United States national forest in southern and central California. Administered by the United States Forest Service, Los Padres includes most of the mountainous land along the California coast from Ventura to Monterey, extending inland. Elevations range from sea level to . Geography The forest is approximately in area, of which or about 88% are public lands; the rest are privately owned inholdings. The forest is divided into two non-contiguous areas separated approximately 40 to 50 miles from one another. The northern division lies within Monterey County and includes the Big Sur Coast and its scenic interior areas. This is a very popular area for hiking, with of hiking trails and 11 campgrounds (ranging from very rugged to suitable for recreational vehicles). The Ventana Wilderness in this division includes the Sisquoc Condor Sanctuary, created in 1937, which is the oldest designated sanctuary for the large endangered birds. The larger, s ...
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Santa Monica Mountains
The Santa Monica Mountains is a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. Because of its proximity to densely populated regions, it is one of the most visited natural areas in California. The Santa Monica Mountains National Recreation Area encompasses this mountain range. Geography The range extends approximately east-west from the Hollywood Hills in Los Angeles to Point Mugu in Ventura County. The western mountains, separating the Conejo Valley from Malibu, suddenly end at Mugu Peak as the rugged, nearly impassible shoreline gives way to tidal lagoons and coastal sand dunes of the alluvial Oxnard Plain. The mountain range contributed to the isolation of this vast coastal plain before regular transportation routes reached western Ventura County. The eastern mountains form a barrier between the San Fernando Valley and the Los Angeles Basin, separating "the Valley" on the north and west-central Los A ...
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Transverse Ranges
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Barbara, Ventura, Los Angeles, San Bernardino, Riverside and Kern counties. The Peninsular Ranges lie to the south. The name Transverse Ranges is due to their east–west orientation, making them transverse to the general northwest–southeast orientation of most of California's coastal mountains.Dibblee Jr, T.W., 1982. Regional geology of the Transverse Ranges Province of southern California. ''Geology and mineral wealth of the California Transverse Ranges'', ''10'', pp.7-26. The ranges extend from west of Point Conception eastward approximately 500 kilometers into the Mojave and Colorado Desert. The geology and topography of the ranges express three distinct segments that have contrasting elevations, rock types, and vegetation. ...
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Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of the Mesozoic, Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic magmatic province, Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago and is marked by an extinction event associated with widespread Anoxic event, oceanic anoxia, ocean acidification, and elevated temperatures likely caused by the eruption of the Karoo-Ferrar, Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and i ...
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Sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually r ...
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