The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is 277 miles long, up to 18 miles wide and attains a depth of over a mile; the canyon and adjacent rim are contained within Grand Canyon National Park, the Kaibab National Forest, Grand Canyon-Parashant National Monument, the Hualapai Indian Reservation, the Havasupai Indian Reservation and the Navajo Nation. President Theodore Roosevelt was a major proponent of preservation of the Grand Canyon area, visited it on numerous occasions to hunt and enjoy the scenery. Nearly two billion years of Earth's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. While some aspects about the history of incision of the canyon are debated by geologists, several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago.
Since that time, the Colorado River has driven the down-cutting of the tributaries and retreat of the cliffs deepening and widening the canyon. For thousands of years, the area has been continuously inhabited by Native Americans, who built settlements within the canyon and its many caves; the Pueblo people considered the Grand Canyon a holy site, made pilgrimages to it. The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540; the Grand Canyon is a river valley in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, is one of the six distinct physiographic sections of the Colorado Plateau province. It is not the deepest canyon in the world. However, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape. Geologically, it is significant because of the thick sequence of ancient rocks that are well preserved and exposed in the walls of the canyon; these rock layers record much of the early geologic history of the North American continent.
Uplift associated with mountain formation moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid; the uplift of the Colorado Plateau is uneven, the Kaibab Plateau that Grand Canyon bisects is over one thousand feet higher at the North Rim than at the South Rim. All runoff from the North Rim flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon; the result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side. Temperatures on the North Rim are lower than those on the South Rim because of the greater elevation. Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon is limited during the winter season due to road closures.
The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years, in part based on apatite /He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma. A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5–6 million years; the study, published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon. There is a substantial amount of controversy because this research suggests such a substantial departure from prior supported scientific consensus. In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years. However, this study has been criticized by those who support the "young canyon" age of around six million years as " attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet.
The major geologic exposures in the Grand Canyon range in age from the 2-billion-year-old Vishnu Schist at the bottom of the Inner Gorge to the 230-million-year-old Kaibab Limestone on the Rim. There is a gap of about a billion years between the 500-million-year-old stratum and the level below it, which dates to about 1.5 billion years ago. This large unconformity indicates a long period. Many of the formations were deposited in warm shallow seas, near-shore environments, swamps as the seashore advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which contains abundant geological evidence of aeolian sand dune deposition. Several parts of the Supai Group were deposited in non–marine environments; the great depth of the Grand Canyon and the height of its strata can be attributed to 5–10 thousand feet of uplift of the Colorado Plateau, starting about 65 million years ago. This uplift has steepened the stream gradient of the Colorado River
The Imperial Valley lies in the California counties of Imperial and Riverside. It is located in southeastern Southern California, is the site of an urban area centered on the city of El Centro; the Valley is bordered by the Colorado River to the east and, in part, the Salton Sea to the west. Farther west lies the San Imperial County border. To the north is the Coachella Valley region of Riverside County, which together with Imperial Valley form the Salton Trough, or the Cahuilla Basin the county line of Imperial and Riverside counties, to the south the international boundary with the U. S. state of California and Baja California. The culture of the area blends those of the United States and Mexico, due to its regional history and geographic location along the international border; the Imperial Valley economy is based on agriculture. Imperial Valley was so named in hopes of attracting settlers. Having done that it is now the home of the El Centro metropolitan area and an economic center of California's government defined "South Border".
Locally, the terms "Imperial Valley" and "Imperial County" are used synonymously. The Imperial Valley extends southward for 50 miles from the southern end of the Salton Sea into Mexico. Part of a trough stretching from the Coachella Valley to the Gulf of California, it is entirely below sea level—235 feet below at the edge of the Salton Sea, its hot desert climate is characterized by daily temperature extremes. It was once part of the Gulf of California, from which it was cut off by the dam-like deposits of the Colorado River Delta Fan as it carved out the Grand Canyon. Bordered by sand dunes and barren mountains, it was uninhabited until 1901, when the Imperial Canal was opened and diverted Colorado River water into the valley through Mexico. Flood-waters in 1905–07 destroyed the irrigation channels and created the Salton Sea now filled by the New River and irrigation run-off; the rivers in the southern part of the Salton Sea river basin flow south to north. The valley is bordered by the Colorado River to the east and, in part, the Salton Sea to the west.
Farther west lies the border with San Diego County and to the south the international boundary between the US state of California and Baja California, Mexico. To the north is the boundary with Riverside County and the Coachella Valley, which with the Imperial Valley form the "Cahuilla Basin" or the "Salton Trough"; the Imperial Valley has summer temperatures well over 100 °F, but from late October until mid-April the temperature is mild and can sometimes reach low temperatures not expected in a desert. During winter months the Valley averages more than eight hours of sunshine a day, receiving the most sunlight of any place in the United States; the lowest minimum temperature recorded in the Imperial Valley was 16 °F on January 22, 1937. The highest maximum temperature recorded was 121 °F on July 28, 1995; the lowest maximum temperature was 42 °F, recorded on January 24, 1949, the highest minimum temperature was 92 °F on June 30, 1946. The highest monthly mean temperature was 95.9 °F, recorded in August 1969 and the lowest mean temperature was 42.3 °F in February 1939.
The 85-year average annual rainfall is 2.93 inches with June being the driest month. The only recorded snowfall in the Valley occurred on December 12, 1932. Snow began falling by 5 a.m. the next day 2.5 inches had been recorded. In the southwest portion of Imperial Valley, 4 inches of snow was reported that day; this was the only snowfall of record to cover the entire valley. The El Centro Metropolitan Area is home to 182,972 residents, according to a 2017 US Census estimate, encompasses the whole Imperial County; the area is in the far southeast region of the State of California. Major population centers are Brawley, El Centro, the county seat. Imperial County had the largest percentage increase in population in California between 2008 and 2009 in the state, according to the California Department of Finance; the county had a population growth rate of 2.2 percent between July 1, 2008, July 1, 2009. The county's growth rate has been one of the top 10 out of 58 counties in California for the past six years.
Last year's growth rate was 2.43 percent. El Centro is the largest industrial center of the Imperial Valley, being the center of shipping exports as well as being home to retail, transportation and agricultural industries. There are two international border crossings nearby for commercial and noncommercial vehicles; the city's population was 37,835 at the 2000 census. The 2006 population is 40,563; the city is 50 feet below the largest city in the United States below sea level. Fifty percent of the jobs in El Centro come from the service and retail sector. Imperial Valley can loosely categorize its cities and communities into three regions: the Salton Beach Towns, Desert Cities, the El Centro area; the Salton Sea Beach Towns have the smallest cities but were resorts in their heyday and have since shrunk in population and size due to the current state of the Salton Sea. The cities and communities of the desert region are outliers in that they are away from urbanized Imperial and tend to be smaller in population than the cities surrounding El Centro.
Cities of the El Centro area tend to be larger than those of the desert and Salton regions. And the southeastern end of California is the state's poorest region with lower-income residents make up over half of the year-round population. Brawley Calexico El Centro Imperial Calipatria Holtville Westmor
Marble Canyon is the section of the Colorado River canyon in northern Arizona from Lee's Ferry to the confluence with the Little Colorado River, which marks the beginning of the Grand Canyon. Lee's Ferry is a common launching point for river runners starting their journey through the Grand Canyon. Marble Canyon is well known for the Navajo Bridge, where US Highway 89A crosses the Colorado River. Marble Canyon marks the western boundary of the Navajo Nation. In 1975, the former Marble Canyon National Monument, which followed the Colorado River northeast from the Grand Canyon to Lee's Ferry, was made part of Grand Canyon National Park; the name Marble Canyon is a misnomer. Although John Wesley Powell knew this when he named the canyon, he thought the polished limestone looked like marble. In his words, "The limestone of the canyon is polished, makes a beautiful marble. Sometimes the rocks are of many colors - white, gray and purple, with saffron tints." Marble Canyon is the site of one of the last great proposed dam projects on the Colorado, the Marble Canyon Dam.
Proposed and investigated in the early 1950s by the United States Bureau of Reclamation, the proposal met substantial opposition, notably from the Sierra Club, when a revived proposal was considered by the state of Arizona as part of the Central Arizona Project from 1965 to 1968. The proposed dam was abandoned in 1968. Exploratory holes, which were drilled in the Redwall Limestone of the canyon walls in an early phase of the abortive project, can still be seen at Mile 39.2. Marble Canyon is the only home of the endangered cactus Pediocactus bradyi
Gulf of California
The Gulf of California is a marginal sea of the Pacific Ocean that separates the Baja California Peninsula from the Mexican mainland. It is bordered by the states of Baja California, Baja California Sur and Sinaloa with a coastline of 4,000 km. Rivers which flow into the Gulf of California include the Colorado, Mayo, Sinaloa and the Yaqui; the gulf's surface area is about 160,000 km2. Depths range from fording at the estuary near Yuma, Arizona, to in excess of 3,000 meters in the deepest parts; the Gulf is thought to be one of the most diverse seas on the planet, is home to more than 5,000 species of micro-invertebrates. Home to over a million people, Baja California is the second-longest peninsula in the world, after the Malay Peninsula in Southeast Asia. Parts of the Gulf of California are a UNESCO World Heritage Site. AreaThe International Hydrographic Organization defines the southern limit of the Gulf of California as: "A line joining Piastla Point in Mexico, the southern extreme of Lower California".
The Gulf of California is 1,126 km long and 48–241 km wide, with an area of 177,000 km2, a mean depth of 818.08 m, a volume of 145,000 km3. The Gulf of California includes three faunal regions: the Northern Gulf of California the Central Gulf of California the Southern Gulf of CaliforniaOne recognized transition zone is termed the Southwestern Baja California Peninsula. Transition zones exist between faunal regions, they vary for each individual species. Geology Geologic evidence is interpreted by geologists as indicating the Gulf of California came into being around 5.3 million years ago as tectonic forces rifted the Baja California Peninsula off the North American Plate. As part of this process, the East Pacific Rise propagated up the middle of the Gulf along the seabed; this extension of the East Pacific Rise is referred to as the Gulf of California Rift Zone. The Gulf would extend as far as Indio, except for the tremendous delta created by the Colorado River; this delta blocks the sea from flooding the Imperial Valleys.
Volcanism dominates the East Pacific Rise. The island of Isla Tortuga is one example of this ongoing volcanic activity. Furthermore, hydrothermal vents due to extension tectonic regime, related to the opening of the Gulf of California, are found in the Bahía de Concepción, Baja California Sur. Islands The Gulf of California contains 37 major islands – the two largest being Isla Ángel de la Guarda and Tiburón Island. Most of the islands are found on the peninsular side of the gulf. In fact, many of the islands of the Sea of Cortez are the result of volcanic explosions that occurred during the early history of Baja California; the islands of Islas Marías, Islas San Francisco, Isla Partida are thought to be the result of such explosions. The formations of the islands, are not dependent on each other, they were each formed as a result of an individual structural occurrence. Several islands, including Isla Coronados, are home to volcanoes; the gulf has islands which together total about 420 hectares.
All of them as a whole were enacted as "Area Reserve and Migratory Bird Refuge and Wildlife" on August 2, 1978. In June 2000, the islands were given a new category "Protection Area Wildlife". In addition to this effort by the Mexican government, for its importance and recognition worldwide, all islands in the Gulf of California are part of the international program "Man and Biosphere" and are part of the World Reserve Network UNESCO Biosphere as Special Biosphere Reserve. Due to the vast expanse covered by this federal protected area conservation and management is carried out through a system of four regional directorates by way of co-direction. There is a regional directorate in the states of Baja California, Baja California Sur and Sinaloa. Notwithstanding the foregoing, the work of direct and indirect conservation is done in the islands is governed by a single Management Program, published in 2000, complemented by local and specific management programs archipelagos; the Directorate of Protection Area Wildlife California Gulf Islands in Baja California is responsible for 56 islands located off the coast of the state.
These are grouped into four archipelagos: San Luis Gonzaga or Enchanted, Guardian Angel, Bahia de los Angeles and San Lorenzo. Shores and tidesThe three general types of shores found in the Gulf of California include rocky shore, sandy beach, tidal flat; some of the rich biodiversity and high endemism that characterize the Gulf of California and make it such a hotspot for fishing can be attributed to insignificant factors, such as the types of rocks that make up a shore. Beaches with softer, more porous rocks have a higher species richness than those with harder, smoother rocks. Porous rocks will have more cracks and crevices in them, making them ideal living spaces for many animals; the rocks themselves, however need to be stable on the shore for a habitat to be stable. Additionally, the color of the rocks can affect the organisms living on a shore. For example, darker rocks will be warmer than lighter ones, can deter animals that do not have a high tolerance for heat. The
California's Colorado Desert is a part of the larger Sonoran Desert. It encompasses 7 million acres, including the irrigated Coachella and Imperial valleys, it is home to fauna. The Colorado Desert is a subdivision of the larger Sonoran Desert encompassing 7 million acres; the desert encompasses Imperial County and includes parts of San Diego County, Riverside County, a small part of San Bernardino County. Most of the Colorado Desert lies at a low elevation, below 1,000 feet, with the lowest point of the desert floor at 275 feet below sea level, at the Salton Sea. Although the highest peaks of the Peninsular Ranges reach elevations of nearly 10,000 feet, most of the region's mountains do not exceed 3,000 feet. In this region, the geology is dominated by the transition of the tectonic plate boundary from rift to fault; the southernmost strands of the San Andreas Fault connect to the northernmost extensions of the East Pacific Rise. The region is subject to earthquakes, the crust is being stretched, which will result in a sinking of the terrain over time.
The Colorado Desert's climate distinguishes it from other deserts. The region experiences greater summer daytime temperatures than higher-elevation deserts and never experiences frost. In addition, the Colorado Desert experiences two rainy seasons per year toward the southern portion of the region; the west coast Peninsular Ranges, or other west ranges, of Southern California–northern Baja California, block most eastern Pacific coastal air and rains, producing an arid climate. Other short or longer-term weather events can move in from the Gulf of California to the south, are active in the summer monsoons; these include remnants of Pacific hurricanes, storms from the southern tropical jetstream, the northern intertropical convergence zone. The region's terrestrial habitats include creosote bush scrub. Higher elevations are dominated by pinyon pine and California juniper, with areas of manzanita and Coulter pine. In addition to hardy perennials, more than half of the desert's plant species are herbaceous annuals, appropriately timed winter rains produce abundant early spring wildflowers.
In the southern portion of the region, the additional moisture supplied by summer rainfall fosters the germination of summer annual plants and supports smoketree and palo verde trees. Common desert wildlife include mule deer, desert kangaroo rat, cactus mouse, black-tailed jackrabbit, Gambel's quail, red-diamond rattlesnake. Among sensitive species are flat-tailed horned lizard, Coachella Valley fringe-toed lizard, desert tortoise, prairie falcon, Andrews' dune scarab beetle, peninsular bighorn sheep, California leaf-nosed bat; the best place to spot wildlife is at the wetland refuges along the Colorado River, Cibola National Wildlife Refuge and Imperial National Wildlife Refuge. In the Colorado Desert's arid environment and wetland habitats are limited in extent but are critically important to wildlife. Runoff from seasonal rains and groundwater springs forms desert arroyos, desert fan palm oases, freshwater marshes, brine lakes, desert washes and perennial streams, desert riparian vegetation communities dominated by cottonwood and non-native tamarisk.
Two of the region's most significant aquatic systems are the Colorado River. While most desert wildlife depend on aquatic habitats as water sources, a number of species, such as the arroyo toad, desert pupfish, Yuma rail, southwestern willow flycatcher, are restricted to these habitats. In some places, summer rains produce short-lived seasonal pools that host uncommon species like Couch's spadefoot toad. Desert fan palm oases are rare, they occur only where permanent water sources are available, such as at springs or along fault lines, where groundwater is forced to the surface by the movement of hard impermeable rock, can be found in the San Jacinto, Santa Rosa, Little San Bernardino mountains, in the canyons of Anza-Borrego Desert State Park, along the San Andreas Fault in the Coachella Valley. The only palm native to California, Washingtonia filifera, grows at the oases; some sub-regions of the Colorado Desert contain endemic flora. Along the Lower Colorado River Valley, in-flow side canyons, flatlands, or low-to-higher level elevations, at least three such flora occur: Hesperocallis undulata, Nolina bigelovii, Peucephyllum schottii.
Joshua Tree National Park Imperial NWR Sonny Bono Salton Sea NWR Indio Hills Palms Anza-Borrego Desert State Park Ocotillo Wells State Vehicular Recreation Area Picacho State Recreation Area Heber Dunes State Vehicular Recreation Area Salton Sea State Recreation Area The Colorado Desert is one of the least-populous regions in California, but human activities have had substantial impacts on the region's habitats and wildlife. Many unique communities aquatic and dune systems, are limited in distribution and separated by vast expanses of inhospitable, arid desert terrain. Limited human disturbances can have markedly deleterious effects on the endemic and sensitive species supported by these unique regional systems; some of the greatest human-caused effects on the region have resulted from the water diversions and flood control measures along the Colorado River. These measures have altered the region's hydrology by redistributing the region's water supp
Arizona is a state in the southwestern region of the United States. It is part of the Western and the Mountain states, it is the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona shares the Four Corners region with Utah and New Mexico. Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912, coinciding with Valentine's Day. Part of the territory of Alta California in New Spain, it became part of independent Mexico in 1821. After being defeated in the Mexican–American War, Mexico ceded much of this territory to the United States in 1848; the southernmost portion of the state was acquired in 1853 through the Gadsden Purchase. Southern Arizona is known for its desert climate, with hot summers and mild winters. Northern Arizona features forests of pine, Douglas fir, spruce trees. There are ski resorts in the areas of Flagstaff and Tucson. In addition to the Grand Canyon National Park, there are several national forests, national parks, national monuments.
About one-quarter of the state is made up of Indian reservations that serve as the home of 27 federally recognized Native American tribes, including the Navajo Nation, the largest in the state and the United States, with more than 300,000 citizens. Although federal law gave all Native Americans the right to vote in 1924, Arizona excluded those living on reservations in the state from voting until the state Supreme Court ruled in favor of Native American plaintiffs in Trujillo v. Garley; the state's name appears to originate from an earlier Spanish name, derived from the O'odham name alĭ ṣonak, meaning "small spring", which applied only to an area near the silver mining camp of Planchas de Plata, Sonora. To the European settlers, their pronunciation sounded like "Arissona"; the area is still known as alĭ ṣonak in the O'odham language. Another possible origin is the Basque phrase haritz ona, as there were numerous Basque sheepherders in the area. A native Mexican of Basque heritage established the ranchería of Arizona between 1734 and 1736 in the current Mexican state of Sonora, which became notable after a significant discovery of silver there, c.
1737. There is a misconception. For thousands of years before the modern era, Arizona was home to numerous Native American tribes. Hohokam and Ancestral Puebloan cultures were among the many that flourished throughout the state. Many of their pueblos, cliffside dwellings, rock paintings and other prehistoric treasures have survived, attracting thousands of tourists each year; the first European contact by native peoples was with Marcos de Niza, a Spanish Franciscan, in 1539. He explored parts of the present state and made contact with native inhabitants the Sobaipuri; the expedition of Spanish explorer Coronado entered the area in 1540–1542 during its search for Cíbola. Few Spanish settlers migrated to Arizona. One of the first settlers in Arizona was José Romo de Vivar. Father Kino was the next European in the region. A member of the Society of Jesus, he led the development of a chain of missions in the region, he converted many of the Indians to Christianity in the Pimería Alta in the 1690s and early 18th century.
Spain founded presidios at Tubac in 1752 and Tucson in 1775. When Mexico achieved its independence from the Kingdom of Spain and its Spanish Empire in 1821, what is now Arizona became part of its Territory of Nueva California known as Alta California. Descendants of ethnic Spanish and mestizo settlers from the colonial years still lived in the area at the time of the arrival of European-American migrants from the United States. During the Mexican–American War, the U. S. Army occupied the national capital of Mexico City and pursued its claim to much of northern Mexico, including what became Arizona Territory in 1863 and the State of Arizona in 1912; the Treaty of Guadalupe Hidalgo specified that, in addition to language and cultural rights of the existing inhabitants of former Mexican citizens being considered as inviolable, the sum of US$15 million dollars in compensation be paid to the Republic of Mexico. In 1853, the U. S. acquired the land south below the Gila River from Mexico in the Gadsden Purchase along the southern border area as encompassing the best future southern route for a transcontinental railway.
What is now known as the state of Arizona was administered by the United States government as part of the Territory of New Mexico until the southern part of that region seceded from the Union to form the Territory of Arizona. This newly established territory was formally organized by the Confederate States government on Saturday, January 18, 1862, when President Jefferson Davis approved and signed An Act to Organize the Territory of Arizona, marking the first official use of the name "Territory of Arizona"; the Southern territory supplied the Confederate government with men and equipment. Formed in 1862, Arizona scout companies served with the Confederate States Army duri