In earth science, erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust, transports it to another location. This natural process is caused by the dynamic activity of erosive agents, that is, ice, air, plants and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind erosion, zoogenic erosion, anthropogenic erosion; the particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Natural rates of erosion are controlled by the action of geological weathering geomorphic drivers, such as rainfall; the rates at which such processes act control. Physical erosion proceeds fastest on steeply sloping surfaces, rates may be sensitive to some climatically-controlled properties including amounts of water supplied, wind speed, wave fetch, or atmospheric temperature.
Feedbacks are possible between rates of erosion and the amount of eroded material, carried by, for example, a river or glacier. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, which control the arrival and emplacement of material at a new location. While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the natural rate of erosion in the region. Excessive erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses.
Water and wind erosion are the two primary causes of land degradation. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, gully erosion. Splash erosion is seen as the first and least severe stage in the soil erosion process, followed by sheet erosion rill erosion and gully erosion. In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles; the distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs.
If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope. Sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are of the order of a few centimetres or less and along-channel slopes may be quite steep; this means that rills exhibit hydraulic physics different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when runoff water accumulates and flows in narrow channels during or after heavy rains or melting snow, removing soil to a considerable depth. Valley or stream erosion occurs with continued water flow along a linear feature; the erosion is both downward, deepening the valley, headward, extending the valley into the hillside, creating head cuts and steep banks.
In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain; the stream gradient becomes nearly flat, lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone
The red fox is the largest of the true foxes and one of the most distributed members of the order Carnivora, being present across the entire Northern Hemisphere from the Arctic Circle to North Africa, North America and Eurasia. It is listed as least concern by the IUCN, its range has increased alongside human expansion, having been introduced to Australia, where it is considered harmful to native mammals and bird populations. Due to its presence in Australia, it is included on the list of the "world's 100 worst invasive species"; the red fox originated from smaller-sized ancestors from Eurasia during the Middle Villafranchian period, colonised North America shortly after the Wisconsin glaciation. Among the true foxes, the red fox represents a more progressive form in the direction of carnivory. Apart from its large size, the red fox is distinguished from other fox species by its ability to adapt to new environments. Despite its name, the species produces individuals with other colourings, including leucistic and melanistic individuals.
Forty-five subspecies are recognised, which are divided into two categories: the large northern foxes, the small, basal southern foxes of Asia and North Africa. Red foxes are together in pairs or small groups consisting of families, such as a mated pair and their young, or a male with several females having kinship ties; the young of the mated pair remain with their parents to assist in caring for new kits. The species feeds on small rodents, though it may target rabbits, game birds, reptiles and young ungulates. Fruit and vegetable matter is eaten sometimes. Although the red fox tends to kill smaller predators, including other fox species, it is vulnerable to attack from larger predators, such as wolves, golden jackals and medium- and large-sized felines; the species has a long history of association with humans, having been extensively hunted as a pest and furbearer for many centuries, as well as being represented in human folklore and mythology. Because of its widespread distribution and large population, the red fox is one of the most important furbearing animals harvested for the fur trade.
Too small to pose a threat to humans, it has extensively benefited from the presence of human habitation, has colonised many suburban and urban areas. Domestication of the red fox is underway in Russia, has resulted in the domesticated red fox. Females are called vixens, young cubs are known as kits. Although the Arctic fox has a small native population in northern Scandinavia, while the corsac fox's range extends into European Russia, the red fox is the only fox native to Western Europe, so is called "the fox" in colloquial British English; the word "fox" comes from Old English. Compare with West Frisian foks, Dutch vos, German Fuchs. This, in turn, derives from Proto-Indo-European *puḱ-'thick-haired. Compare to the Hindi pū̃ch'tail', Tocharian B päkā'tail; the bushy tail forms the basis for the fox's Welsh name, literally'bushy', from llwyn'bush'. Portuguese: raposa from rabo'tail', Lithuanian uodẽgis from uodegà'tail', Ojibwa waagosh from waa, which refers to the up and down "bounce" or flickering of an animal or its tail.
The scientific term vulpes derives from the Latin word for fox, gives the adjectives vulpine and vulpecular. The red fox is considered a more specialised form of Vulpes than the Afghan and Bengal foxes in the direction of size and adaptation to carnivory, it is, not as adapted for a purely carnivorous diet as the Tibetan fox. The species is Eurasian in origin, may have evolved from either Vulpes alopecoides or the related Chinese V. chikushanensis, both of which lived during the Middle Villafranchian. The earliest fossil specimens of V. vulpes were uncovered in Baranya, Hungary dating from 3.4-1.8 million years ago. The ancestral species was smaller than the current one, as the earliest red fox fossils are smaller than modern populations; the earliest fossil remains of the modern species date back to the mid-Pleistocene in association with the refuse of early human settlements. This has led to the theory that the red fox was hunted by primitive humans as both a source of food and pelts. Red foxes colonised the North American continent in two waves: during or before the Illinoian glaciation, during the Wisconsinan glaciation.
Gene mapping demonstrates that red foxes in North America have been isolated from their Old World counterparts for over 400,000 years, thus raising the possibility that speciation has occurred, that the previous binomial name of Vulpes fulva may be valid. In the far north, red fox fossils have been found in Sangamonian deposits in the Fairbanks District and Medicine Hat. Fossils dating from the Wisconsian are present in 25 sites in Arkansas, Colorado, Missouri, New Mexico, Texas and Wyoming. Although they ranged far south during the Wisconsinan, the onset of warm conditions shrank their range toward the north, have only reclaimed their former American ranges because of human-induced environmental changes. Genetic testing indicates two distinct red fox refugia exist in North America, which have been separated since the Wisconsinan; the northern refugium occurs in Alaska and western Canada, consists of the large subspecies V. v. alascensis, V. v. abietorum, V. v. regalis, V. v. rubricosa. The southern refugium occurs in the subalpine parklands and alpine meadows of the Rocky Mountains, the Cascade Range, Sierra Nevada
Crotaphytus is a genus of lizards known as collared lizards. They are a genus of small to medium-sized predators indigenous to arid environments of the southwestern regions of North America; the following species and subspecies are recognized as being valid. Crotaphytus antiquus Axtell & Webb, 1995 – venerable collared lizard Crotaphytus bicinctores N. M. Smith & W. W. Tanner, 1972 – Great Basin collared lizard or desert collared lizard Crotaphytus collaris – common collared lizard Crotaphytus collaris auriceps Fitch & W. W. Tanner, 1951 – yellow-headed collared lizard Crotaphytus collaris baileyi Stejneger, 1890 – western collared lizard Crotaphytus collaris collaris – eastern collared lizard Crotaphytus collaris fuscus Ingram & W. W. Tanner, 1971 – Chihuahuan collared lizard Crotaphytus collaris melanomaculatus Axtell & Webb, 1995 – black-spotted collared lizard Crotaphytus dickersonae K. P. Schmidt, 1922 – Mexican collared lizard Crotaphytus grismeri McGuire, 1994 – Grismer's collared lizard Crotaphytus insularis Van Denburgh & Slevin, 1921 Crotaphytus nebrius Axtell & Montanucci, 1977 – Sonoran collared lizard Crotaphytus reticulatus Baird, 1858 – reticulated collared lizard Crotaphytus vestigium N.
M. Smith & W. W. Tanner, 1972 – Baja California collared lizardNota bene: A binomial authority in parentheses or a trinomial authority in parentheses indicates that the species or subspecies was described in a genus other than Crotaphytus. In 1969, Oklahoma designated its first state reptile. Citations BibliographyHolbrook JE. North American Herpetology. Vol. II.. Philadelphia: J. Dobson. 142 pp.. Shearer, Benjamin F.. State Names, Seals and Symbols. Westport, Connecticut: Greenwood Publishing Group. ISBN 0-313-28862-3. Photos of genus members
Moab is a city on the southern edge of Grand County in southeastern Utah in the western United States. The population was 5,046 at the 2010 census, in 2017 the population was estimated to be 5,253, it is largest city in Grand County. Moab attracts a large number of tourists every year visitors to the nearby Arches and Canyonlands national parks; the town is a popular base for mountain bikers who ride the extensive network of trails including the Slickrock Trail, for off-roaders who come for the annual Moab Jeep Safari. The Biblical name Moab refers to an area of land located on the eastern side of the Jordan River; some historians believe the city in Utah came to use this name because of William Andrew Peirce, the first postmaster, believing that the biblical Moab and this part of Utah were both "the far country". However, others believe the name has Paiute origins, referring to the word moapa, meaning "mosquito"; some of the area's early residents attempted to change the city's name, because in the Christian Bible, Moabites are demeaned as incestuous and idolatrous.
One petition in 1890 had 59 signatures and requested a name change to "Vina". Another effort attempted to change the name to "Uvadalia". Both attempts failed. During the period between 1829 and the early 1850s, the area around what is now Moab served as the Colorado River crossing along the Old Spanish Trail. Latter-day Saint settlers attempted to establish a trading fort at the river crossing called the Elk Mountain Mission in April 1855 to trade with travellers attempting to cross the river. Forty men were called on this mission. There were repeated Indian attacks, including one on September 23, 1855, in which James Hunt, companion to Peter Stubbs, was shot and killed by a Native American. After this last attack, the fort was abandoned. A new round of settlers from Rich County, led by Randolph Hockaday Stewart, established a permanent settlement in 1878 under the direction of Brigham Young. Moab was incorporated as a town on December 20, 1902. In 1883 the Denver and Rio Grande Western Railroad main line was constructed across eastern Utah.
The rail line did not pass through Moab, instead passing through the towns of Thompson Springs and Cisco, 40 miles to the north. Other places to cross the Colorado were constructed, such as Lee's Ferry, Navajo Bridge and Boulder Dam; these changes shifted. Moab farmers and merchants had to adapt from trading with passing travelers to shipping their goods to distant markets. Soon Moab's origins as one of the few natural crossings of the Colorado River were forgotten; the U. S. military deemed the bridge over the Colorado River at Moab important enough to place it under guard as late as World War II. In 1943, a former Civilian Conservation Corps camp outside Moab was used to confine Japanese American internees labeled "troublemakers" by authorities in the War Relocation Authority, the government body responsible for overseeing the wartime incarceration program; the Moab Isolation Center for "noncompliant" Japanese Americans was created in response to growing resistance to WRA policies within the camps.
On January 11, 1943, the sixteen men who had initiated the two-day protests were transferred to Moab from the town jails where they were booked after the riot. Having closed just fifteen months prior, all 18 military-style structures of the CCC camp were in good condition, the site was converted to its new use with minimal renovation. 150 military police guarded the camp, director Raymond Best and head of security Francis Frederick presided over administration. On February 18, thirteen transfers from Gila River, were brought to Moab, six days ten more arrived from Manzanar. An additional fifteen Tule Lake inmates were transferred on April 2. Most of these new arrivals were removed from the general camp population because of their resistance to the WRA's attempts to determine the loyalty of incarcerated Japanese Americans, met with confusion and anger because of a lack of explanation as to how and why internees would be assessed; the Moab Isolation Center remained open until April 27, when most of its inmates were bused to the larger and more secure Leupp Isolation Center.
In 1994, the "Dalton Wells CCC Camp/Moab Relocation Center" was added to the National Register of Historic Places, although no marker exists on the site, an information plaque at the current site entrance and a photograph on display at the Dan O'Laurie Museum in Moab mention the former isolation center. Moab's economy was based on agriculture, but shifted to mining. Uranium and vanadium were discovered in the area in the 1920s. Potash and manganese came next, oil and gas were discovered. In the 1950s Moab became the so-called "Uranium Capital of the World" after geologist Charles Steen found a rich deposit of uranium ore south of the city; this discovery coincided with the advent of the era of nuclear weapons and nuclear power in the United States, Moab's boom years began. The city population grew nearly 500% over the next few years, bringing the population to near 6,000 people; the explosion in population caused much construction of schools. Charles Steen donated a great deal of money and land to create new houses and
A natural arch, natural bridge, or rock arch is a natural rock formation where an arch has formed with an opening underneath. Natural arches form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion from the sea, rivers or weathering. Most natural arches are formed from narrow fins and sea stacks composed of sandstone or limestone with steep vertical, cliff faces; the formations become narrower due to erosion over geologic time scales. The softer rock stratum erodes away creating rock shelters, or alcoves, on opposite sides of the formation beneath the harder stratum, or caprock, above it; the alcoves erode further into the formation meeting underneath the harder caprock layer, thus creating an arch. The erosional processes exploit weaknesses in the softer rock layers making cracks larger and removing material more than the caprock; the choice between bridge and arch is somewhat arbitrary. The Natural Arch and Bridge Society identifies a bridge as a subtype of arch, water-formed.
By contrast, the Dictionary of Geological Terms defines a natural bridge as a "natural arch that spans a valley of erosion."The largest natural arch, by a significant margin, is the Xianren Bridge in China, with a span of 122 ± 5 meters. On coasts two different types of arches can form depending on the geology. On discordant coastlines rock types run at 90° to the coast. Wave refraction concentrates the wave energy on the headland, an arch forms when caves break through the headland. Two examples of this type of arch are London Arch—previously known as London Bridge—in Victoria and Neill Island in the Andaman Islands, India; when these arches collapse, they form stacks and stumps. On concordant coastlines rock types run parallel to the coastline, with weak rock such as shale protected by stronger rock such as limestone; the wave action along concordant coastlines breaks through the strong rock and erodes the weak rock quickly. Good examples of this type of arch are the Durdle Door and Stair Hole near Lulworth Cove on Dorset's Jurassic Coast in south England.
When Stair Hole collapses it will form a cove. Weather-eroded arches begin their formation as deep cracks. Erosion occurring within the cracks wears away exposed rock layers and enlarges the surface cracks isolating narrow sandstone walls which are called fins. Alternating frosts and thawing cause crumbling and flaking of the porous sandstone and cut through some of the fins; the resulting holes become weathering. The arches collapse leaving only buttresses that in time will erode. Many weather-eroded arches are found in Arches National Park, Canyonlands National Park, Grand Staircase-Escalante National Monument, all located in southern Utah, United States; some natural bridges may look like arches, but they form in the path of streams that wear away and penetrate the rock. Pothole arches form by chemical weathering as water collects in natural depressions and cuts through to the layer below. Natural Bridges National Monument in Utah protects the area surrounding three large natural bridges, all of which were formed by streams running through canyons, the largest of, named Sipapu Bridge with a span of 225 feet.
The Rainbow Bridge National Monument's namesake was formed by flowing water which created the largest known natural bridge in the Western Hemisphere with a span of 234 feet, based on a laser measurement made in 2007. Xianren Bridge known as Fairy Bridge, in Guangxi, China is the world's largest known natural bridge with a span recorded at 400 feet by the Natural Arch and Bridge Society in October 2010, with a precision of ±15 feet. Natural bridges can form from natural limestone caves, where paired sinkholes collapse and a ridge of stone is left standing in between, with the cave passageway connecting from sinkhole to sinkhole. Like all rock formations, natural bridges are subject to continued erosion, will collapse and disappear. One example of this was the double-arched Victorian coastal rock formation, London Bridge, which lost an arch after storms increased erosion. Moon Hill in Yangshuo, Guizhou Province, China, is an example of an arch formed by the remnant of a karst limestone cave. In a few places in the world, natural arches are utilized by humans as transportation bridges with highways or railroads running across them.
In Virginia, US Route 11 traverses Natural Bridge. Two additional natural arch roadways are found in Kentucky; the first arch, a cave erosion arch made of limestone, is located in Carter Caves State Resort Park and it has a paved road on top. The second arch, a weather-eroded sandstone arch with a dirt road on top, is located on the edge of Natural Bridge State Park in Kentucky; the latter arch is called White's Branch Arch and the road going over it is referred to as the Narrows Road. In Europe, the Romanian village of Ponoarele has a road 60 m long and 13 m wide, passing over a stone arch 4 m thick, 20 m high, with a 9 m span; the arch is called God's Bridge. In South America, the railroad from Lima, Peru crosses the Rio Yauli on a natural bridge near kilometer 214.2 as it approaches the city of La Oroya, Peru. Aloba Arch, Chad Boatswain Bird Island, Ascension Island Bogenfels, Namibia Goedehoop natural rock bridge, South Africa Hole-in-the-Wall, Eastern Cape, South Africa Tassili n'Ajjer and Tadrart Rouge, two mountain ranges with many arches, Algeria Tukuyu natural bridge, Ta
Prospecting is the first stage of the geological analysis of a territory. It is the physical search for minerals, precious metals or mineral specimens, is known as fossicking. Prospecting is a small-scale form of mineral exploration, an organised, large scale effort undertaken by commercial mineral companies to find commercially viable ore deposits. Prospecting is physical labour, involving traversing, panning and outcrop investigation, looking for signs of mineralisation. In some areas a prospector must make claims, meaning they must erect posts with the appropriate placards on all four corners of a desired land they wish to prospect and register this claim before they may take samples. In other areas publicly held lands are open to prospecting without staking a mining claim; the traditional methods of prospecting involved combing through the countryside through creek beds and along ridgelines and hilltops on hands and knees looking for signs of mineralisation in the outcrop. In the case of gold, all streams in an area would be panned at the appropriate trap sites looking for a show of'colour' or gold in the river trail.
Once a small occurrence or show was found, it was necessary to intensively work the area with pick and shovel, via the addition of some simple machinery such as a sluice box and winnows, to work the loose soil and rock looking for the appropriate materials. For most base metal shows, the rock would have been mined by hand and crushed on site, the ore separated from the gangue by hand; these shows were short-lived and abandoned quite soon, requiring the prospector to move onwards to the next and bigger and better show. Though, the prospector would strike it rich and be joined by other prospectors and larger-scale mining would take place. Although these are thought of as "old" prospecting methods, these techniques are still used today but coupled with more advanced techniques such as geophysical magnetic or gravity surveys. In most countries in the 19th and early 20th century, it was unlikely that a prospector would retire rich if he was the one who found the greatest of lodes. For instance Patrick Hannan, who discovered the Golden Mile, died without receiving anywhere near a fraction of the value of the gold contained in the lodes.
The same story repeated at Bendigo, Ballarat and California. In the United States and Canada prospectors were lured by the promise of gold and other precious metals, they traveled across the mountains of the American West, carrying picks and gold pans. The majority of early prospectors had no training and relied on luck to discover deposits. Other gold rushes occurred in Papua New Guinea, Australia at least four times, in South Africa and South America. In all cases, the gold rush was sparked by idle prospecting for gold and minerals which, when the prospector was successful, generated'gold fever' and saw a wave of prospectors comb the countryside. Modern prospectors today rely on training, the study of geology, prospecting technology. Knowledge of previous prospecting in an area helps in determining location of new prospective areas. Prospecting includes geological mapping, rock assay analysis, sometimes the intuition of the prospector. Metal detectors are invaluable for gold prospectors, as they are quite effective at detecting gold nuggets within the soil down to around 1 metre, depending on the acuity of the operator's hearing and skill.
Magnetic separators may be useful in separating the magnetic fraction of a heavy mineral sand from the nonmagnetic fraction, which may assist in the panning or sieving of gold from the soil or stream. Prospecting pickaxes are used to scrape at rocks and minerals, obtaining small samples that can be tested for trace amounts of ore. Modern prospecting pickaxes are sometimes equipped with magnets, to aid in the gathering of ferromagnetic ores. Prospecting pickaxes are equipped with a triangular head, with a sharp point. Bioprospecting Geobotanical prospecting Gold prospecting Gold Prospectors Association of America Gold rush Mineral exploration Mining Oil exploration United States Geological Survey Metal Detector Prospecting in Tasmania Prospecting in Nova Scotia Prospecting in Northwestern Ontario Historical pictures of prospectors and the Gold Rush Prospecting in the West Prospecting in Indonesia