In geology and physical geography, a plateau called a high plain or a tableland, is an area of a highland consisting of flat terrain, raised above the surrounding area with one or more sides with steep slopes. Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, erosion by water and glaciers. Plateaus are classified according to their surrounding environment as intermontane, piedmont, or continental. Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, erosion by water and glaciers. Volcanic plateaus are produced by volcanic activity; the Columbia Plateau in the northwestern United States is an example. They may be formed by upwelling of volcanic extrusion of lava; the underlining mechanism in forming plateaus from upwelling starts when magma rises from the mantle, causing the ground to swell upward. In this way, flat areas of rock are uplifted to form a plateau. For plateaus formed by extrusion, the rock is built up from lava spreading outward from cracks and weak areas in the crust.
Plateaus can be formed by the erosional processes of glaciers on mountain ranges, leaving them sitting between the mountain ranges. Water can erode mountains and other landforms down into plateaus. Dissected plateaus are eroded plateaus cut by rivers and broken by deep narrow valleys. Computer modeling studies suggest that high plateaus may be a result from the feedback between tectonic deformation and dry climatic conditions created at the lee side of growing orogens. Plateaus are classified according to their surrounding environment. Intermontane plateaus are the highest in the world, bordered by mountains; the Tibetan Plateau is one such plateau. Lava or volcanic plateaus are the plateau; the magma that comes out through narrow cracks or fissures in the crust spread over large area and solidifies. These layers of lava sheets form volcanic plateaus; the Antrim plateau in Northern Ireland, The Deccan Plateau in India and the Columbia Plateau in the United States are examples of lava plateaus. Piedmont plateaus are bordered on one side by mountains and on the other by a sea.
The Piedmont Plateau of the Eastern United States between the Appalachian Mountains and the Atlantic Coastal Plain is an example. Continental plateaus are bordered on all sides by oceans, forming away from the mountains. An example of a continental plateau is the Antarctic Polar Plateau in East Antarctica; the largest and highest plateau in the world is the Tibetan Plateau, sometimes metaphorically described as the "Roof of the World", still being formed by the collisions of the Indo-Australian and Eurasian tectonic plates. The Tibetan plateau covers 2,500,000 km2, at about 5,000 m above sea level; the plateau is sufficiently high to reverse the Hadley cell convection cycles and to drive the monsoons of India towards the south. The second-highest plateau is the Deosai Plateau of the Deosai National Park at an average elevation of 4,114 m, it is located in northern Pakistan. Deosai means'the land of giants'; the park protects an area of 3,000 km2. It is known for its rich flora and fauna of the Karakoram-West Tibetan Plateau alpine steppe ecoregion.
In spring it is covered by a wide variety of butterflies. The highest point in Deosai is Deosai Lake, or Sheosar Lake from the Shina language meaning "Blind lake" near the Chilim Valley; the lake lies at an elevation of 4,142 m, one of the highest lakes in the world, is 2.3 km long, 1.8 km wide, 40 m deep on average. Some other major plateaus in Asia are: Najd in the Arabian Peninsula elevation 762 to 1,525 m, Armenian Highlands, Iranian plateau, Anatolian Plateau, Mongolian Plateau, the Deccan Plateau. Another large plateau is the icy Antarctic Plateau, sometimes referred to as the Polar Plateau, home to the geographic South Pole and the Amundsen-Scott South Pole Station, which covers most of East Antarctica where there are no known mountains but rather 3,000 m high of superficial ice and which spreads slowly toward the surrounding coastline through enormous glaciers; this polar ice cap is so massive that the echolocation sound measurements of ice thickness have shown that large parts of the Antarctic "dry land" surface have been pressed below sea level.
Thus, if that same ice cap were removed, the large areas of the frozen white continent would be flooded by the surrounding Antarctic Ocean or Southern Ocean. On the other hand, were the ice cap melts away too the surface of the land beneath it would rebound away through isostasy from the center of the Earth and that same land would rise above sea level. A large plateau in North America is the Colorado Plateau, which covers about 337,000 km2 in Colorado, Utah and New Mexico. In northern Arizona and southern Utah the Colorado Plateau is bisected by the Colorado River and the Grand Canyon. How this came to be is that over 10 million years ago, a river was there, though not on the same cours
West Virginia is a state located in the Appalachian region in the Southern United States, considered to be a part of the Middle Atlantic States. It is bordered by Pennsylvania to the north, Maryland to the east and northeast, Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest. West Virginia is the 41st largest state by area, is ranked 38th in population; the capital and largest city is Charleston. West Virginia became a state following the Wheeling Conventions of 1861, after the American Civil War had begun. Delegates from some Unionist counties of northwestern Virginia decided to break away from Virginia, although they included many secessionist counties in the new state. West Virginia was admitted to the Union on June 20, 1863, was a key border state during the war. West Virginia was the only state to form by separating from a Confederate state, the first to separate from any state since Maine separated from Massachusetts, was one of two states admitted to the Union during the American Civil War.
While a portion of its residents held slaves, most of the residents were yeomen farmers, the delegates provided for gradual abolition of slavery in the new state Constitution. The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States; however the Bureau of Labor Statistics classifies West Virginia as a part of the Mid-Atlantic. The northern panhandle extends adjacent to Pennsylvania and Ohio, with the West Virginia cities of Wheeling and Weirton just across the border from the Pittsburgh metropolitan area, while Bluefield is less than 70 miles from North Carolina. Huntington in the southwest is close to the states of Ohio and Kentucky, while Martinsburg and Harpers Ferry in the Eastern Panhandle region are considered part of the Washington metropolitan area, in between the states of Maryland and Virginia; the unique position of West Virginia means that it is included in several geographical regions, including the Mid-Atlantic, the Upland South, the Southeastern United States.
It is the only state, within the area served by the Appalachian Regional Commission. The state is noted for its mountains and rolling hills, its significant logging and coal mining industries, its political and labor history, it is known for a wide range of outdoor recreational opportunities, including skiing, whitewater rafting, hiking, mountain biking, rock climbing, hunting. Many ancient man-made earthen mounds from various prehistoric mound builder cultures survive in the areas of present-day Moundsville, South Charleston, Romney; the artifacts uncovered in these give evidence of village societies. They had a tribal trade system culture. In the 1670s during the Beaver Wars, the powerful Iroquois, five allied nations based in present-day New York and Pennsylvania, drove out other American Indian tribes from the region in order to reserve the upper Ohio Valley as a hunting ground. Siouan language tribes, such as the Moneton, had been recorded in the area. A century the area now identified as West Virginia was contested territory among Anglo-Americans as well, with the colonies of Pennsylvania and Virginia claiming territorial rights under their colonial charters to this area before the American Revolutionary War.
Some speculative land companies, such as the Vandalia Company, the Ohio Company and Indiana Company, tried to legitimize their claims to land in parts of West Virginia and present day Kentucky, but failed. This rivalry resulted in some settlers petitioning the Continental Congress to create a new territory called Westsylvania. With the federal settlement of the Pennsylvania and Virginia border dispute, creating Kentucky County, Kentuckians "were satisfied, the inhabitants of a large part of West Virginia were grateful."The Crown considered the area of West Virginia to be part of the British Virginia Colony from 1607 to 1776. The United States considered this area to be the western part of the state of Virginia from 1776 to 1863, before the formation of West Virginia, its residents were discontented for years with their position in Virginia, as the government was dominated by the planter elite of the Tidewater and Piedmont areas. The legislature had electoral malapportionment, based on the counting of slaves toward regional populations, the western white residents were underrepresented in the state legislature.
More subsistence and yeoman farmers lived in the west and they were less supportive of slavery, although many counties were divided on their support. The residents of this area became more divided after the planter elite of eastern Virginia voted to secede from the Union during the Civil War. Residents of the western and northern counties set up a separate government under Francis Pierpont in 1861, which they called the Restored Government. Most voted to separate from Virginia, the new state was admitted to the Union in 1863. In 1864 a state constitutional convention drafted a constitution, ratified by the legislature without putting it to popular vote. West Virginia abolished slavery by a gradual process and temporarily disenfranchised men who had held Confederate office or fought for the Confederacy. West Virginia's history has been profoundly affected by its mountainous terrain and vast river valleys, rich natural resources; these were all factors driving its economy and the lifestyles of its residents, who tended to live in many small isolated communities in the mountain valleys.
A 2010 analysis of
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
Seneca Rocks is a large crag and local landmark in Pendleton County in the Eastern Panhandle of West Virginia, USA. The south peak is one of a small number of peaks inaccessible except by technical rock climbing techniques on the East Coast of the United States. One of the best-known scenic attractions in West Virginia, the sheer rock faces are a popular challenge for rock climbers. Seneca Rocks is visible from, accessible by way of, West Virginia Route 28, West Virginia Route 55 and U. S. Route 33 in the Spruce Knob-Seneca Rocks National Recreation Area of the Monongahela National Forest; the three highways converge in the hamlet of Seneca Rocks, named for the cliffs nearby. Seneca Rocks is at the north end of the River Knobs, which contain several other similar "razorback" ridges or "fins" such as Judy Rocks and Nelson Rocks, all on the western flank of North Fork Mountain. Seneca Rocks is a prominent and visually striking formation rising nearly 900 feet above the confluence of Seneca Creek with the North Fork of the South Branch of the Potomac River.
It overlooks the community of Seneca Rocks known as "Mouth of Seneca". The Rocks consist with a central notch between. A prominent pinnacle — "the Gendarme" — occupied the notch; the west flank of the Wills Mountain Anticline in the area of Seneca Rocks consists of geological strata that have been upended and rotated 90 degrees to form the impressive crag as well as other prominent outcroppings of the erosion-resistant white/gray Tuscarora quartzite, including nearby Champe Rocks. The Anticline is a gigantic upward bulge formed more than 200 million years ago at the end of the Paleozoic Era; the quartzite is 250 feet thick here, located on exposed ridges as caprock or exposed crags. The rock is composed of fine grains of sand that were laid down in the Silurian Period some 440 million years ago, in an extensive sand shoal at the edge of the ancient Iapetus Ocean. Eons of geologic activity followed, as the ocean closed and the underlying rock uplifted and folded. Millions of years of erosion stripped away the overlying rock and left remnants of the arching folds in the form of these landmark outcrops.
Evidence suggests that the Native Americans of the Archaic Period may have camped at the mouth of nearby Seneca Creek at the foot of the Rocks. The famous Great Indian Warpath, known locally as the "Seneca Trail", followed the Potomac River, allowing the Algonquian and Seneca nations to transit the area for purposes of trade and war. Excavation for the building of the present Seneca Rocks Visitor Center uncovered evidence of two villages, the more recent of which thrived about 600 years ago. About a dozen dwellings were found; the first European visitors to see the region were surveyors who passed through around 1746, the first settlers arrived at Mouth of Seneca fifteen years later. At that time, West Virginia was the edge of the great wilderness; the Rocks were visited and sketched by the well-known writer and magazine illustrator David Hunter Strother around 1853. His sketches were reworked and published two decades as a popular wood engraving in an 1872 issue of Harpers New Monthly Magazine..
It is unknown. Undoubtedly Native Americans scaled the rocks prior to European settlers reaching the area, but there is no record of their ascents; the historic ascent of Paul Bradt, Don Hubbard, Sam Moore in 1939 found an inscription of "D. B. September 16, 1908." This has been attributed to a surveyor named Bittenger, known to be working in the area. The documented climbing history of the Rocks begins in 1935 with a roped descent - the ascent was a steep hike – of the North Peak by Paul Bradt and Florence Perry. In the 1930s and 40's only a few climbers from the Washington, D. C. and Pittsburgh areas, attempted to climb Seneca Rocks. In 1943 and'44, as part of the West Virginia Maneuver Area, 10th Mountain Division of the U. S. Army used Seneca and Champe Rocks to train mountain troops in assault climbing in preparation for action in the Apennines of Italy, they left behind an estimated 75 thousands soft iron pitons, some of which can still be found on the rocks, which inspired one of the faces to be named "The Face of a Thousand Pitons".
The Spruce Knob-Seneca Rocks National Recreation Area was established within the Monongahela National Forest by an act of the U. S. Congress on September 28, 1965; the Rocks themselves were purchased by the federal government in 1969 from the heirs of D. C. Harper; the original visitor center was opened in 1978, constructed on a grant of $297,000. A 1985 flood damaged the facility. On October 22, 1987, "the Gendarme", an isolated and prominent pinnacle of the Rocks, fell to the ground. On May 26, 1992, the visitor center was destroyed by arson; the current visitor center — known as the Seneca Rocks Discovery Center — was completed in the fall of 1998 on a 5 million dollar grant. The "Seneca Rock" turnpoint at 38°50′03″N 79°22′04″W has been used by glider pilots for gliding competitions and soaring awards because its distinctive appearance in aerial photographs made it suitable for photo documentation of the flight performance; this turnpoint was used on many 500 kilometer out-and-return course flights from Ridge Soaring Gliderport in Julian, including an October 15, 1995, flight by Canadian pilot Walter Weir, recognized as a world record at the time.
Seneca Rocks is a popular location for recreational rock climbing. There are 375 major mapped climbing routes, varying in degree from 5.0 to 5.13. There are two climbing schools located in Seneca Rocks that
New Mexico is a state in the Southwestern region of the United States of America. It is one of the Mountain States and shares the Four Corners region with Utah and Arizona. With a population around two million, New Mexico is the 36th state by population. With a total area of 121,592 sq mi, it is the fifth-largest and sixth-least densely populated of the 50 states. Due to their geographic locations and eastern New Mexico exhibit a colder, alpine climate, while western and southern New Mexico exhibit a warmer, arid climate; the economy of New Mexico is dependent on oil drilling, mineral extraction, dryland farming, cattle ranching, lumber milling, retail trade. As of 2016–2017, its total gross domestic product was $95 billion with a GDP per capita of $45,465. New Mexico's status as a tax haven yields low to moderate personal income taxes on residents and military personnel, gives tax credits and exemptions to favorable industries; because of this, its film industry contributed $1.23 billion to its overall economy.
Due to its large area and economic climate, New Mexico has a large U. S. military presence marked notably with the White Sands Missile Range. Various U. S. national security agencies base their research and testing arms in New Mexico such as the Sandia and Los Alamos National Laboratories. During the 1940s, Project Y of the Manhattan Project developed and built the country's first atomic bomb and nuclear test, Trinity. Inhabited by Native Americans for many thousands of years before European exploration, it was colonized by the Spanish in 1598 as part of the Imperial Spanish viceroyalty of New Spain. In 1563, it was named Nuevo México after the Aztec Valley of Mexico by Spanish settlers, more than 250 years before the establishment and naming of the present-day country of Mexico. After Mexican independence in 1824, New Mexico became a Mexican territory with considerable autonomy; this autonomy was threatened, however, by the centralizing tendencies of the Mexican government from the 1830s onward, with rising tensions leading to the Revolt of 1837.
At the same time, the region became more economically dependent on the United States. At the conclusion of the Mexican–American War in 1848, the United States annexed New Mexico as the U. S. New Mexico Territory, it was admitted to the Union as the 47th state on January 6, 1912. Its history has given New Mexico the highest percentage of Hispanic and Latino Americans, the second-highest percentage of Native Americans as a population proportion. New Mexico is home to part of the Navajo Nation, 19 federally recognized Pueblo communities of Puebloan peoples, three different federally recognized Apache tribes. In prehistoric times, the area was home to Ancestral Puebloans and the modern extant Comanche and Utes inhabited the state; the largest Hispanic and Latino groups represented include the Hispanos of New Mexico and Mexican Americans. The flag of New Mexico features the state's Spanish origins with the same scarlet and gold coloration as Spain's Cross of Burgundy, along with the ancient sun symbol of the Zia, a Puebloan tribe.
These indigenous, Mexican and American frontier roots are reflected in the eponymous New Mexican cuisine and the New Mexico music genre. New Mexico received its name long before the present-day nation of Mexico won independence from Spain and adopted that name in 1821. Though the name “Mexico” itself derives from Nahuatl, in that language it referred to the heartland of the Empire of the Mexicas in the Valley of Mexico far from the area of New Mexico, Spanish explorers used the term “Mexico” to name the region of New Mexico in 1563. In 1581, the Chamuscado and Rodríguez Expedition named the region north of the Rio Grande "San Felipe del Nuevo México"; the Spaniards had hoped to find wealthy indigenous Mexica cultures there similar to those of the Aztec Empire of the Valley of Mexico. The indigenous cultures of New Mexico, proved to be unrelated to the Mexicas, they were not wealthy, but the name persisted. Before statehood, the name "New Mexico" was applied to various configurations of the U.
S. territory, to a Mexican state, to a province of New Spain, all in the same general area, but of varying extensions. With a total area of 121,699 square miles, the state is the fifth-largest state of the US, larger than British Isles. New Mexico's eastern border lies along 103°W longitude with the state of Oklahoma, 2.2 miles west of 103°W longitude with Texas. On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, with Chihuahua making up about 90% of that; the western border with Arizona runs along the 109° 03'W longitude. The southwestern corner of the state is known as the Bootheel; the 37°N parallel forms the northern boundary with Colorado. The states of New Mexico, Colorado and Utah come together at the Four Corners in New Mexico's northwestern corner. New Mexico has no natural water sources
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
Beds are the layers of sedimentary rocks that are distinctly different from overlying and underlying subsequent beds of different sedimentary rocks. Layers of beds are called strata, they are formed from sedimentary rocks being deposited on the Earth's solid surface over a long periods of time. The stratigraphy are layered in the same order that they were deposited, allowing a differentiation of which beds are younger and which ones are older; the structure of a bed is determined by its bedding plane. Beds can be differentiated including rock or mineral type and particle size; the term is applied to sedimentary strata, but may be used for volcanic flows or ash layers. In a quarry, bedding is a term used for a structure occurring in granite and similar massive rocks that allows them to split in well-defined planes horizontally or parallel to the land surface. Other kinds of beds are graded beds. Cross beds are not layered horizontally and are formed by a combination of local deposition on the inclined surfaces of ripples or dunes, local erosion.
Graded beds shows a gradual change in clast sizes from one side of the bed to the other. A normal grading is when there are bigger grain sizes on the older side while an inverse grading is when there are smaller grain sizes on the older side. By knowing the type of beds, geologists can determine the relative ages of the rocks. A bed is the smallest lithostratigraphic unit ranging in thickness from a centimeter to several meters and distinguishable from beds above and below it; the thickness of the bed is determined by the time period involving the deposition of the rocks. Thick Bed - 100cm Thick Bed - 30cm Medium Bed - 10cm Thin Bed - 3cm Very Thin Bed - 1cm Thinner than 1cm is called a Lamina In geotechnical engineering a bedding plane forms a discontinuity that may have a large influence on the mechanical behaviour of soil and rock masses in, for example, foundation, or slope construction. There are geologic principles that the beds follow. Though there can be cases where the principles do not apply due to faults, they are true for most cases.
Law of Superposition is the law that states that the oldest rocks are deposited first and has the younger layers deposited last, as long as the beds have not been overturned through tectonic activities. This is used to date their relative ages. Law of Original Horizontality states that if the beds are not horizontal the layers were caused to either fold or tilt through tectonic activities, they were all deposited horizontally due to gravity. Law of Lateral Continuity states; this means that if two places separated by erosional features have similar rocks, it could mean that they were continuous. Cross-Cutting Relationship states, it helps with dating the rocks. Geological unit Lamination Stratigraphy Stratum Lamina, Laminaset and Bedset. Campbell, Charles V. Sedimentology, vol. 8, issue 1, pp. 7-26