An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to toss people around and destroy whole cities; the seismicity, or seismic activity, of an area is the frequency and size of earthquakes experienced over a period of time. The word tremor is used for non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground; when the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can trigger landslides, volcanic activity. In its most general sense, the word earthquake is used to describe any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused by rupture of geological faults, but by other events such as volcanic activity, mine blasts, nuclear tests.
An earthquake's point of initial rupture is called its hypocenter. The epicenter is the point at ground level directly above the hypocenter. Tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane; the sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the fault surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of stick-slip behavior. Once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface; this continues until the stress has risen sufficiently to break through the asperity allowing sliding over the locked portion of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, cracking of the rock, thus causing an earthquake.
This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior. There are three main types of fault, all of which may cause an interplate earthquake: normal and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip and movement on them involves a vertical component. Normal faults occur in areas where the crust is being extended such as a divergent boundary. Reverse faults occur in areas.
Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip. Reverse faults those along convergent plate boundaries are associated with the most powerful earthquakes, megathrust earthquakes, including all of those of magnitude 8 or more. Strike-slip faults continental transforms, can produce major earthquakes up to about magnitude 8. Earthquakes associated with normal faults are less than magnitude 7. For every unit increase in magnitude, there is a thirtyfold increase in the energy released. For instance, an earthquake of magnitude 6.0 releases 30 times more energy than a 5.0 magnitude earthquake and a 7.0 magnitude earthquake releases 900 times more energy than a 5.0 magnitude of earthquake. An 8.6 magnitude earthquake releases the same amount of energy as 10,000 atomic bombs like those used in World War II. This is so because the energy released in an earthquake, thus its magnitude, is proportional to the area of the fault that ruptures and the stress drop.
Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The topmost, brittle part of the Earth's crust, the cool slabs of the tectonic plates that are descending down into the hot mantle, are the only parts of our planet which can store elastic energy and release it in fault ruptures. Rocks hotter than about 300 °C flow in response to stress; the maximum observed lengths of ruptures and mapped faults are 1,000 km. Examples are the earthquakes in Chile, 1960; the longest earthquake ruptures on strike-slip faults, like the San Andreas Fault, the North Anatolian Fault in Turkey and the Denali Fault in Alaska, are about half to one third as long as the lengths along subducting plate margins, those along normal faults are shorter. The most important parameter controlling the maximum earthquake magnitude on a fault is however not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins, the dip angle of the rupture plane is shallow about 10 de
Elgin is a city in Bastrop and Travis Counties in the U. S. state of Texas. The population was 8,135 at the 2010 census; the city is a suburb of Austin, is part of the Greater Austin metropolitan area. Elgin is known as the Sausage Capital of Texas and the Brick Capital of the Southwest, due to the presence of three operating brickyards in the mid-20th century; the City of Elgin owes its existence to a major flood of the Colorado River in 1869. The railroad was to have run from McDade, 10 miles east of Elgin, southwest to the Colorado River at a point somewhere between Bastrop and Webberville to Austin following the river. In 1871, the Houston and Texas Central Railroad built through the area and established a flag stop called Glasscock named for George W. Glasscock, a local resident and Republic of Texas soldier who lived in the area in the 1830s. Glasscock was renamed on August 18, 1872, for Robert Morris Elgin, the railroad's land commissioner, following the practice of naming new railroad towns after officers of the company.
Elgin was established. The original plat placed the train depot in the center of a one-square-mile area. Elgin was incorporated, received a post office the following year, a Baptist Sunday school began meeting in a private home. Much of the town's early population was drawn from nearby Perryville, which the railroad had bypassed. Perryville, or Hogeye as it was nicknamed, was located 2.5 miles to the south. The town was known by three different names: the name Young's Settlement was chosen in honor of the Michael Young family; the post office was named Young's Settlement, the churches and Masonic Lodge carried the name Perryville. The name Hogeye was given to the stage stop at the Litton home where dances were held and, according to legend, the fiddler knew only one tune: "Hogeye", which he played over and over as the crowd danced on the puncheon floor. In 1879, Elgin was described as a "thriving depot town" of 400, it had a newspaper, a gin, a gristmill. Three years Methodists erected the first church building in town.
In 1884, Elgin had five general stores, two druggists, three cotton gins, a saloon. In 1885, a group of citizens met in Elgin to organize a new north-south railroad which would run from Taylor, the rail head for the Missouri and Texas Railroad 16 miles to the north, through Elgin to Bastrop, the county seat, 16 miles to the south; the Taylor and Bastrop Railroad was formed in 1886 and began building the line. That same year, the "Katy" continued the construction on to Houston. Thus, Elgin became the beneficiary of two major rail lines with eight passenger trains daily, adding to Elgin's business as a shipping point for cotton and livestock. By 1890, Elgin had a population of 1,100 and supported two hotels, a broom factory, two doctors, a dentist, the Elgin Courier newspaper; the next year oil was discovered 5 miles southeast of town. Coal proved better for the economy, when the large coal belt nearby was mined in the early 20th century, bringing Latin-Americans and African-Americans to the area.
The year 1900 resulted in a bumper crop of Elgin prospered. Elgin grew but through the 20th century, from 1,258 in 1904 to 4,846 in 1990; the city incorporated in 1901, electing Charles Gillespie, building contractor, as mayor, as well as J. D. Hemphill as marshal, W. E. McCullough, J. Wed Davis, Ed Lawhon, Max Hirach, F. S. Wade as aldermen. Local law enforcement was established to enforce newly established criminal codes. By 1910, Elgin was enjoying a period of great prosperity as families from out on the prairie and surrounding communities moved to town and built nice homes. By 1940, Elgin was the site of two big brick and tile plants. Elgin enterprise was stimulated during World War II by the proximity of the army training facility Camp Swift. A third brick company was established in the town in the mid-1950s, lured by the high-quality clay deposits in the area. In addition to the brick plants, a local sausage factory processed thousands of pounds of beef and pork a week. Five cotton gins and a cotton oil mill were in operation at the same time.
Other industries included grain processing and hydraulic press manufacturing. By the 1980s, proximity to Austin had begun to attract commuters to Elgin. In the mid-1980s, the Elgin Courier was still being published, the sausage had achieved wider fame, two brick and tile plants were still in operation. Elgin was the site of a furniture plant and a leather works; the Elgin Commercial Historic District includes 14 city blocks of commercial and industrial buildings. Most of these buildings are constructed of locally produced brick and were erected from 1872 to 1947; the Elgin Commercial Historic District was added to the National Register of Historic Places in 1996. Within the 14-block district, 67 buildings are considered contributing structures. A contributing structure is one. Southside includes Central Avenue C in the downtown district. Five buildings are under restoration in the Southside area. During the past 14 years, private property owners, business owners, the public sector have invested about $9 million in the downtown are
Georgetown is a city in and the county seat of Williamson County, United States, with a population of 47,400 at the 2010 census and a population of 63,716 at the 2016 Census estimate. It is 30 miles from Austin. Southwestern University, the oldest university in Texas, founded in 1840, is located in Georgetown about one-half mile from the historic square. Sun City Texas is a large retirement-oriented and age-restricted development that constitutes more than one-third of Georgetown's population. Georgetown has a notable range of Victorian residential architecture. In 1976, a local historic ordinance was passed to recognize and protect the significance of the historic central business district, in 1977, the Williamson County Courthouse Historical District, containing some 46 contributing structures, was listed on the National Register of Historic Places. Georgetown is known as the "Red Poppy" Capital of Texas for the red poppy wildflowers planted throughout the city. Georgetown's Red Poppy Festival, which attracts up to 30,000 visitors annually, is held in April each year on the historic square.
Georgetown has been the site of human habitation since at least 9,000 BC, considerably before that. The earliest known inhabitants of the county, during the late Pleistocene, can be linked to the Clovis culture, a Paleo-Indian culture characterized by the manufacture of distinctive "Clovis points" that first appeared around 9200 BC, as early as 11,500 BC, at the end of the last glacial period. One of the most important discoveries in recent times is that of the ancient skeletal remains dubbed the "Leanderthal Lady" because of its age and proximity to a nearby community Leander, Texas; the site is southwest of Georgetown and was discovered by accident by Texas Department of Transportation workers while core samples for a new highway were being drilled. The site has been extensively studied for many years, samples carbon date the findings to the Pleistocene period, about 10,500 years ago. Archeological dig sites showing a much greater evidence of Archaic period inhabitants have been found in burned rock middens at several sites along the San Gabriel that are now inundated by Granger Lake and at the confluence of the North and South San Gabriel Rivers in Georgetown.
The earliest known historical occupants of the county, the Tonkawas, were a flint-working, hunting people who followed buffalo on foot and periodically set fire to the prairie to aid them in their hunts. During the 18th century, they made the transition to a horse culture and used firearms to a limited extent. Small numbers of Kiowa, Yojuane and Mayeye Indians were living in the county at the time of the earliest Anglo settlements; as these native populations thinned due to non-indigenous settlements, the Comanches still continued to raid native peoples settlements in the county until the 1860s. Georgetown was named for George Washington Glasscock. Early American and Swedish pioneers were attracted to the area's abundance of timber and good, clear water. In addition, the land was fertile. Georgetown is the county seat of Williamson County, formed on March 13, 1848, after the early settlers petitioned the state legislature to create it out of Milam County; the county was to have been named San Gabriel County, but was instead named after Robert McAlpin Williamson, a Texas statesman and judge at the time.
Georgetown was an agrarian community for most of the early 20th centuries. The Shawnee Trail, a cattle trail that led from Texas to the rail centers in Kansas and Missouri, crossed through Georgetown; the establishment of Southwestern University in 1873 and construction of a railroad in 1878 contributed to the town's growth and importance. A stable economy developed, based on agricultural activity. Cotton was the dominant crop in the area between the 1920s. Williamson County was once the top producer of cotton in Texas. To transport cattle and bales of cotton, at one time, Georgetown was served by two national railroads, the International-Great Northern Railroad, merged into the Missouri Pacific, the Missouri–Kansas–Texas Railroad; the regional Georgetown and Granger Railroad was completed to Austin in 1904. Georgetown is served by the appropriately named Georgetown Railroad, a'short line' railroad that uses portions of the former M-K-T and the I-GN to connect with the Union Pacific Railroad at Round Rock and at Granger.
Extensive damage and loss of life throughout the county from a 1921 flood led Georgetown to seek flood control. A low-pressure system from a hurricane settled in over Williamson County and brought more than 23 inches of rain in Taylor and more than 18 inches of rain in Georgetown. An estimated 156 persons perished in many of them farm laborers; the flood and its horrific destruction culminated in the building of a dam on the north fork of the San Gabriel River to create and impound Lake Georgetown, which opened on October 5, 1979. Both Georgetown and Round Rock own the water rights to Lake Georgetown for municipal water use. Population growth and industrial expansion continued modestly in the 20th century until about 1960, when residential and industrial development, due to major growth and urban expansion of nearby Austin accelerated. In 2008, Fortune Small Business magazine named Georgetown the number-two best city in the nation to "live and launch" a new business. In March 2015, Georgetown announced that their municipal-owned utility, Georgetown Utility Systems, would begin buying 100% of its power for its customers from wind and solar farms by 2017, effective
University of Texas at Austin
The University of Texas at Austin is a public research university in Austin, Texas. It is the flagship institution of the University of Texas System; the University of Texas was inducted into the Association of American Universities in 1929, becoming only the third university in the American South to be elected. The institution has the nation's eighth-largest single-campus enrollment, with over 50,000 undergraduate and graduate students and over 24,000 faculty and staff. A Public Ivy, it is a major center for academic research, with research expenditures exceeding $615 million for the 2016–2017 school year; the university houses seven museums and seventeen libraries, including the Lyndon Baines Johnson Library and Museum and the Blanton Museum of Art, operates various auxiliary research facilities, such as the J. J. Pickle Research Campus and the McDonald Observatory. Among university faculty are recipients of the Nobel Prize, Pulitzer Prize, the Wolf Prize, the Primetime Emmy Award, the Turing Award, the National Medal of Science, as well as many other awards.
As of October 2018, 11 Nobel Prize winners, 2 Turing Award winners and 1 Fields medalist have been affiliated with the school as alumni, faculty members or researchers. Student athletes are members of the Big 12 Conference, its Longhorn Network is the only sports network featuring the college sports of a single university. The Longhorns have won four NCAA Division I National Football Championships, six NCAA Division I National Baseball Championships, thirteen NCAA Division I National Men's Swimming and Diving Championships, has claimed more titles in men's and women's sports than any other school in the Big 12 since the league was founded in 1996; the first mention of a public university in Texas can be traced to the 1827 constitution for the Mexican state of Coahuila y Tejas. Although Title 6, Article 217 of the Constitution promised to establish public education in the arts and sciences, no action was taken by the Mexican government. After Texas obtained its independence from Mexico in 1836, the Texas Congress adopted the Constitution of the Republic, under Section 5 of its General Provisions, stated "It shall be the duty of Congress, as soon as circumstances will permit, to provide, by law, a general system of education."On April 18, 1838, "An Act to Establish the University of Texas" was referred to a special committee of the Texas Congress, but was not reported back for further action.
On January 26, 1839, the Texas Congress agreed to set aside fifty leagues of land—approximately 288,000 acres —towards the establishment of a publicly funded university. In addition, 40 acres in the new capital of Austin were reserved and designated "College Hill." In 1845, Texas was annexed into the United States. The state's Constitution of 1845 failed to mention higher education. On February 11, 1858, the Seventh Texas Legislature approved O. B. 102, an act to establish the University of Texas, which set aside $100,000 in United States bonds toward construction of the state's first publicly funded university. The legislature designated land reserved for the encouragement of railroad construction toward the university's endowment. On January 31, 1860, the state legislature, wanting to avoid raising taxes, passed an act authorizing the money set aside for the University of Texas to be used for frontier defense in west Texas to protect settlers from Indian attacks. Texas's secession from the Union and the American Civil War delayed repayment of the borrowed monies.
At the end of the Civil War in 1865, The University of Texas's endowment was just over $16,000 in warrants and nothing substantive had been done to organize the university's operations. This effort to establish a University was again mandated by Article 7, Section 10 of the Texas Constitution of 1876 which directed the legislature to "establish and provide for the maintenance and direction of a university of the first class, to be located by a vote of the people of this State, styled "The University of Texas."Additionally, Article 7, Section 11 of the 1876 Constitution established the Permanent University Fund, a sovereign wealth fund managed by the Board of Regents of the University of Texas and dedicated for the maintenance of the university. Because some state legislators perceived an extravagance in the construction of academic buildings of other universities, Article 7, Section 14 of the Constitution expressly prohibited the legislature from using the state's general revenue to fund construction of university buildings.
Funds for constructing university buildings had to come from the university's endowment or from private gifts to the university, but the university's operating expenses could come from the state's general revenues. The 1876 Constitution revoked the endowment of the railroad lands of the Act of 1858, but dedicated 1,000,000 acres of land, along with other property appropriated for the university, to the Permanent University Fund; this was to the detriment of the university as the lands the Constitution of 1876 granted the university represented less than 5% of the value of the lands granted to the university under the Act of 1858. The more valuable lands reverted to the fund to support general educat
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl
The Ouachita Mountains referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of deformed Paleozoic strata constituting the Ouachita Fold and Thrust Belt, one of the important orogenic belts of North America; the Ouachitas continue in the subsurface to the southeast where they make a poorly understood connection with the Appalachians and to the southwest where they join with the Marathon area of West Texas. Together with the Ozark Plateaus, the Ouachitas form the U. S. Interior Highlands; the highest natural point is Mount Magazine at 2,753 feet. Louis R. Harlan claimed that "Ouachita" is composed of the Choctaw words ouac for buffalo and chito for large, together meaning "country of large buffaloes". At one time, herds of buffalo inhabited the lowland areas of the Ouachitas. Historian Muriel H. Wright wrote that "Ouachita" is composed of the Choctaw words owa for hunt and chito for big, together meaning "big hunt far from home".
According to the article Ouachita in the Encyclopedia of Oklahoma History and Culture, "Ouachita" comes from the French spelling of the Caddo word washita, meaning "good hunting grounds". The Ouachitas are a major physiographic province of Arkansas and Oklahoma and are grouped with the Arkansas River Valley. Together with the Ozark Plateaus, the Ouachitas form the U. S. Interior Highlands, one of few mountainous regions between the Appalachians and Rockies; the Ouachitas are dominated by pine and hickory. The shortleaf pine and post oak are common in upland areas; the maple-leaf oak is found at only four sites worldwide. Some native tree species, such as the eastern red-cedar, are colonizers of human-disturbed sites; the Ouachita National Forest covers 1.8 million acres of the Ouachitas. It is one of the largest and oldest national forests in the Southern U. S. created through an executive order by President Theodore Roosevelt on December 18, 1907. There are six wilderness areas within the Ouachita National Forest, which are protected areas designed to minimize the impacts of human activities.
Bison and elk once have since been extirpated. Today, there are large populations of white-tailed deer and other common temperate forest animals. Though elusive, hundreds of black bear roam the Ouachitas. Several species of salamander are endemic to the Ouachitas and have traits that vary from one locale to another; the Athens Piedmont consists of a series of none exceeding 1,000 feet. It is located south of the Ouachitas and extends from Arkadelphia, Arkansas to the Arkansas-Oklahoma border; the Athens Piedmont runs through Clark, Howard and Sevier counties in Arkansas and McCurtain County in Oklahoma. The Caddo and Missouri mountains are a high, compact group of mountains composed of the weather-resistant Arkansas Novaculite, they are located in Montgomery and Polk counties, Arkansas. The highest natural point is Raspberry Mountain at 2,358 feet; the headwaters of multiple rivers are found in this area, including the Caddo and Little Missouri rivers. The Cross Mountains are located in Polk and Sevier counties, Arkansas and McCurtain County, Oklahoma.
The highest natural point is Whiskey Peak at 1,670 feet. The Crystal Mountains are located in Montgomery County, Arkansas, they are so named because of the occurrence of some of the world's finest quartz. The Crystal Mountains are taller than the nearby Zig Zag Mountains, achieving elevations over 1,800 feet; the Fourche Mountains are a long, continuous chain of mountains composed of the weather-resistant Jackfork Sandstone. They extend from Pulaski County, Arkansas to Atoka County and are home to several popular sites of interest, including Pinnacle Mountain State Park near Little Rock, Arkansas; the highest natural point is Rich Mountain at 2,681 feet, which intersects the Arkansas-Oklahoma border near Mena, Arkansas. The Fourche Mountains form a major watershed divide between the Arkansas River Basin to the north and the Red River Basin to the south; the Frontal Ouachita Mountains are located in the Arkansas River Valley and feature a number of isolated landforms. The highest natural point is Mount Magazine at 2,753 feet, the highest natural point of the Ouachitas and U.
S. Interior Highlands; the Frontal Ouachita Mountains are structurally quite different from the rest of the Ouachitas and are sometimes considered a separate range. The Trap Mountains are located in Garland and Hot Spring counties, Arkansas; the highest natural point is Trap Mountain at 1,310 feet. The Zig Zag Mountains are located in Garland County and are home to the thermal springs of Hot Springs National Park, they are so named because of their unique chevron shape when viewed from above, the result of plunging anticlines and synclines. The Zig Zag Mountains do reach heights over 1,400 feet; the Ouachitas are formed by a thick succession of deformed Paleozoic strata constituting the Ouachita Fold and Thrust Belt, which outcrops for 220 miles in western Arkansas and southeastern Oklahoma. In a general sense, the Ouachitas are considered an anticlinorium because the oldest known rocks are located towards the center of the outcrop area; the Ouachitas continue in the subsurface to the Black Warrior Basin of Alabama and Mississippi where they plunge towards the Appalachian Mountains.
To the southwest, the Ouachitas join with the Marathon area of west Texas where rocks of the Ouachita Fold and Thrust Belt are exposed. Unlike many ranges in the United St
Washingtonia filifera known as desert fan palm, California fan palm or California palm, is a flowering plant in the palm family native to the far southwestern United States and Baja California. Growing to 15–20 m tall by 3–6 m broad, it is an evergreen monocot with a tree-like growth habit, it has waxy, fan-shaped leaves. Other common names include California fan petticoat palm; the specific epithet filifera means "thread-bearing". W. filifera is the only palm native to the Western United States and the country's largest native palm. Primary populations are found in desert riparian habitats at spring-fed and stream-fed oases in the Colorado Desert and at a few scattered locations in the Mojave Desert, it is found near watercourses in the Sonoran Desert along the Gila River in Yuma, along the Hassayampa River and near New River in Maricopa County, in portions of Pima County, Pinal County, Mohave County, several other isolated locations in Clark County, Nevada. It is a naturalized species in the warm springs near Death Valley and in the extreme northwest of Sonora.
It is reportedly naturalized in the Southeast, Hawaii, the U. S. Virgin Islands, Australia. W. filifera grows to 18 m in height in ideal conditions. The California fan palm is known as the desert fan palm, American cotton palm, Arizona fan palm; the fronds are up to 4 m long, made up of a petiole up to 2 m long, bearing a fan of leaflets 1.5–2.0 m long. They have long, thread-like, white fibers, the petioles are pure green with yellow edges and filifera-filaments, between the segments; the trunk is gray and tan, the leaves are gray green. When the fronds die, they remain drop down to cloak the trunk in a wide skirt; the shelter that the skirt creates provides a microhabitat for invertebrates. If any red color is present on petioles or trunk, it is not a pure W. filifera, but a W. fila-busta hybrid. W. filifera lives from 80 to 250 years or more. Desert fan palms provide habitat for the giant palm-boring beetle, western yellow bat, hooded oriole, many other bird species. Hooded orioles places to build nests.
Numerous insect species visit the hanging inflorescences. The palm boring beetle Dinapate wrightii can chew through the trunks of other palms. A continued infestation of beetles can kill various genera and species of palms. W. filifera appears to be resistant to the red palm weevil via a mechanism of antibiosis — production of compounds lethal to the larvae. The desert fan palm is experiencing a population and range expansion due to global warming or removing excess mustangs. Natural oases are restricted to areas downstream from the source of hot springs, though water is not always visible at the surface. Grazing animals can kill young plants through trampling, or by eating the terminus at the apical meristem, the growing portion of the plant; this may have kept palms restricted to a lesser range than indicated by the availability of water. Today's oasis environment may have been protected from colder climatic changes over the course of its evolution. Thus, this palm is restricted by both water and climate to separated relict groves.
The trees in these groves show little if any genetic differentiation, suggesting that the genus is genetically stable. Joshua Tree National Park in the Mojave Desert preserves and protects healthy riparian palm habitat examples in the Little San Bernardino Mountains, westward where water rises through the San Andreas Fault on the east valley side. In the central Coachella Valley, the Indio Hills Palms State Reserve and nearby Coachella Valley Preserve, other large oases are protected and accessible; the Santa Rosa and San Jacinto Mountains National Monument, Anza-Borrego Desert State Park both have large and diverse W. filifera canyon oasis habitats. The fruit of the fan palm was eaten raw, cooked, or ground into flour for cakes; the Cahuilla and related tribes used the leaves to make sandals, thatch roofs, baskets. The stems were used to make cooking utensils; the Moapa band of Paiutes and other Southern Paiutes have written memories of using this palm's seed, fruit, or leaves for various purposes including starvation food.
W. filifera is cultivated as an ornamental tree. It is one of the hardiest Coryphoidiae palms, rated as hardy to USDA hardiness zone 8, it can survive brief temperatures of −10 °C with minor damage, established plants have survived, with severe leaf damage, brief periods as low as −12 °C. The plants grow best in Mediterranean climates, but can be found in humid subtropical climates such as eastern Australia and the southeastern USA, it has gained the Royal Horticultural Society's Award of Garden Merit. Johnson. "Washingtonia filifera". IUCN Red List of Threatened Species. Version 2006. International Union for Conservation of Nature. Retrieved 11 May 2006. Floridata.com: Washingtonia filifera Cornett, J. W. 2010. Desert Palm Oasis. Nature Trails Press, Palm Springs, California. Interactive Distribution Map for Washingtonia filifera USDA Plants Profile: Washingtonia filifera UC Jepson Manual treatment — Washingtonia filifera Calflora Database: Washingtonia filifera Washingtonia filifera in Flora of North America Washingtonia filifera — U.
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