The Andes or Andean Mountains are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. This range is about 7,000 km long, about 200 to 700 km wide, of an average height of about 4,000 m; the Andes extend from north to south through seven South American countries: Venezuela, Ecuador, Bolivia and Argentina. Along their length, the Andes are split into several ranges, separated by intermediate depressions; the Andes are the location of several high plateaus – some of which host major cities such as Quito, Bogotá, Medellín, Sucre, Mérida and La Paz. The Altiplano plateau is the world's second-highest after the Tibetan plateau; these ranges are in turn grouped into three major divisions based on climate: the Tropical Andes, the Dry Andes, the Wet Andes. The Andes Mountains are the world's highest mountain range outside Asia; the highest mountain outside Asia, Argentina's Mount Aconcagua, rises to an elevation of about 6,961 m above sea level.
The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to the equatorial bulge resulting from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m; the Andes are part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica. The etymology of the word Andes has been debated; the majority consensus is that it derives from the Quechua word anti, which means "east" as in Antisuyu, one of the four regions of the Inca Empire. The Andes can be divided into three sections: The Southern Andes in Chile. In the northern part of the Andes, the isolated Sierra Nevada de Santa Marta range is considered to be part of the Andes; the term cordillera comes from the Spanish word "cordel", meaning "rope".
The Andes range is about 200 km wide throughout its length, except in the Bolivian flexure where it is about 640 kilometres wide. The Leeward Antilles islands Aruba and Curaçao, which lie in the Caribbean Sea off the coast of Venezuela, were thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between the South American and Caribbean plates; the Andes are a Mesozoic–Tertiary orogenic belt of mountains along the Pacific Ring of Fire, a zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of tectonic plate processes, caused by the subduction of oceanic crust beneath the South American Plate, it is the result of a convergent plate boundary between the Nazca Plate and the South American Plate The main cause of the rise of the Andes is the compression of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate.
To the east, the Andes range is bounded by several sedimentary basins, such as Orinoco, Amazon Basin, Madre de Dios and Gran Chaco, that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and a less rugged topography; the Andes Mountains contain large quantities of iron ore located in many mountains within the range. The Andean orogen has a series of oroclines; the Bolivian Orocline is a seaward concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point, the orientation of the Andes turns from Northwest in Peru to South in Chile and Argentina; the Andean segment north and south of the orocline have been rotated 15° to 20° counter clockwise and clockwise respectively.
The Bolivian Orocline area overlaps with the area of maximum width of the Altiplano Plateau and according to Isacks the orocline is related to crustal shortening. The specific point at 18° S where the coastline bends is known as the "Arica Elbow". Further south lies the Maipo Orocline or Maipo Transition Zone located between 30° S and 38°S with a break in trend at 33° S. Near the southern tip of the Andes lies the Patagonian orocline; the western rim of the South American Plate has been the place of several pre-Andean orogenies since at least the late Proterozoic and early Paleozoic, when several terranes and microcontinents collided and amalgamated with the ancient cratons of eastern South America, by the South American part of Gondwana. The formation of the modern Andes began with the events of the Triassic when Pangaea began the break up that resulted in developing several rifts; the development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east.
The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress and erosion. Tectonic forces above the subduction zone al
Little Colorado River
The Little Colorado River is a tributary of the Colorado River in the U. S. state of Arizona, providing the principal drainage from the Painted Desert region. Together with its major tributary, the Puerco River, it drains an area of about 26,500 square miles in eastern Arizona and western New Mexico. Although it stretches 340 miles, only the headwaters and the lowermost reaches flow year-round. Between St. Johns and Cameron, most of the river is a wide, braided wash, only containing water after heavy snowmelt or flash flooding; the lower 57.2 miles is known as the Little Colorado River Gorge and forms one of the largest arms of the Grand Canyon, at over 3,000 feet deep where it joins the Colorado near Desert View in Grand Canyon National Park. The river rises in Apache County; the West Fork starts in a valley on the north flank of Mount Baldy at an elevation of nearly 10,000 feet, while the East Fork starts nearby. The forks meet in a canyon near the town of Greer, it flows into River Reservoir leaves the canyon near Eagar.
The river turns north, meandering through Richville Valley, before emptying into Lyman Lake, impounded by an irrigation dam built in 1912. From there the river continues north, past the town of St. Johns. Shortly afterwards, the river transforms from a perennial stream to an ephemeral wash as it travels northwestwards through Hunt Valley, where it receives the Zuni River receiving Silver Creek and the Puerco River—its main tributaries—near the town of Holbrook as it flows into the Painted Desert; the Little Colorado passes Joseph City and crosses the Southern Transcon route of the BNSF Railway, now winding north into Coconino County. The river enters the Navajo Nation, drops over the 185-foot Grand Falls of the Little Colorado shortly after. Below Grand Falls, the river flows through a rugged canyon for about 15 miles. Emerging into the desert again, the Little Colorado skirts the eastern edge of Wupatki National Monument and passes the town of Cameron, where it is bridged by U. S. Highway 89.
From Cameron, the Little Colorado River carves an steep and narrow gorge into the Colorado Plateau achieving a maximum depth of about 3,200 feet. The depth of the canyon is such that groundwater is forced to the surface, forming numerous springs that restore a perennial river flow, it joins the Colorado deep inside miles from any major settlement. The confluence marks the end of the Marble Canyon segment of the Grand Canyon and the beginning of Upper Granite Gorge; the Little Colorado River is one of the two major tributaries of the Colorado River in Arizona, the other being the Gila River. Runoff peaks twice a year, first in the early spring from snow melt and highland rain; the annual runoff is variable with the possibility of no flow occurring due to a weak snow pack or lack of summer rain. Conversely, years such as 1949, 1973, 1979, 1983 and 1993 have seen massive volumes of spring snowmelt while large monsoon runoff has occurred in 1955, 1964, 1984 and 2006. Monthly average flows in the springtime average several hundred cfs and can reach 2,000 to 3,000 cubic feet per second.
Only the upper reaches of the river above St. Johns, the lowermost stretch below Cameron, flow year round. According to a streamflow gauge near Cameron, before the river enters the Grand Canyon, the river's average annual flow was 367.2 cubic feet per second from 1948 to present. The highest annual average was 1,127 cubic feet per second in 1973, the lowest was 14.1 cubic feet per second in 2000. The river's peak flows can be far higher than its average flow, because of quick desert runoff from cloudbursts. At the same gauge, peak flows were recorded from 1923 to 2008, with spotty data from 1924 to 1947; the highest recorded peak was 120,000 cubic feet per second on September 20, 1923, while the lowest was 1,590 cubic feet per second in 1974. Human activity in the Little Colorado River watershed dates back to the early Holocene epoch, in the last glacial period. Nomadic hunter-gatherers inhabited the water-rich and diverse upper basin of the Little Colorado for 8,000 years before the Navajo and Hopi tribes populated the area.
Many of these people practiced small-scale irrigation in riverside villages, located in sheltered canyons and cliffs that provided defense. Early Spanish explorers exploring the Grand Canyon area were most the first Europeans to see the Little Colorado River, they called it the Little Colorado. Other than fur trappers and mountain men, one of the first organized expeditions into the area of the Little Colorado River was led by Amiel Weeks Whipple in 1853–54 during one of the expeditions to map out a route for a transcontinental railroad. Called The Great Railroad Expeditions, or Pacific Railroad Surveys, Whipple's expedition consisted of several teams going along the 35th parallel from Albuquerque to the Pacific, following the Santa Fe Trail route; the Little Colorado River known as the Flax River, the first Rio Chiquito, is depicted and labelled as such on a map compiled by Lt. Joseph C. Ives and published in the official volumes of those expeditions. Ives would again return to the area in 1858 after navigating a steamboat named the Explorer up the Colorado from south of Yuma northwards to Black Canyon, at which point his party went
The Himalayas, or Himalaya, form a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has many including the highest, Mount Everest; the Himalayas include over fifty mountains exceeding 7,200 m in elevation, including ten of the fourteen 8,000-metre peaks. By contrast, the highest peak outside Asia is 6,961 m tall. Lifted by the subduction of the Indian tectonic plate under the Eurasian Plate, the Himalayan mountain range runs west-northwest to east-southeast in an arc 2,400 km long, its western anchor, Nanga Parbat, lies just south of the northernmost bend of Indus river. Its eastern anchor, Namcha Barwa, is just west of the great bend of the Yarlung Tsangpo River; the Himalayan range is bordered on the northwest by the Hindu Kush ranges. To the north, the chain is separated from the Tibetan Plateau by a 50–60 km wide tectonic valley called the Indus-Tsangpo Suture. Towards the south the arc of the Himalaya is ringed by the low Indo-Gangetic Plain.
The range varies in width from 350 km in the west to 150 km in the east. The Himalayas are distinct from the other great ranges of central Asia, although sometimes the term'Himalaya' is loosely used to include the Karakoram and some of the other ranges; the Himalayas are inhabited by 52.7 million people, are spread across five countries: Nepal, Bhutan and Pakistan. Some of the world's major rivers – the Indus, the Ganges and the Tsangpo-Brahmaputra – rise in the Himalayas, their combined drainage basin is home to 600 million people; the Himalayas have a profound effect on the climate of the region, helping to keep the monsoon rains on the Indian plain and limiting rainfall on the Tibetan plateau. The Himalayas have profoundly shaped the cultures of the Indian subcontinent; the name of the range derives from himá and ā-laya. They are now known as the "Himalaya Mountains" shortened to the "Himalayas", they were described in the singular as the Himalaya. This was previously transcribed Himmaleh, as in Emily Dickinson's poetry and Henry David Thoreau's essays.
The mountains are known as the Himālaya in Nepali and Hindi, the Himalaya or'The Land of Snow' in Tibetan, the Hamaleh Mountain Range in Urdu and the Ximalaya Mountain Range in Chinese. In the middle of the great curve of the Himalayan mountains lie the 8,000 m peaks of Dhaulagiri and Annapurna in Nepal, separated by the Kali Gandaki Gorge; the gorge splits the Himalayas into Western and Eastern sections both ecologically and orographically – the pass at the head of the Kali Gandaki, the Kora La is the lowest point on the ridgeline between Everest and K2. To the east of Annapurna are the 8,000 m peaks of Manaslu and across the border in Tibet, Shishapangma. To the south of these lies Kathmandu, the capital of Nepal and the largest city in the Himalayas. East of the Kathmandu Valley lies valley of the Bhote/Sun Kosi river which rises in Tibet and provides the main overland route between Nepal and China – the Araniko Highway/China National Highway 318. Further east is the Mahalangur Himal with four of the world's six highest mountains, including the highest: Cho Oyu, Everest and Makalu.
The Khumbu region, popular for trekking, is found here on the south-western approaches to Everest. The Arun river drains the northern slopes of these mountains, before turning south and flowing through the range to the east of Makalu. In the far east of Nepal, the Himalayas rise to the Kanchenjunga massif on the border with India, the third highest mountain in the world, the most easterly 8,000 m summit and the highest point of India; the eastern side of Kanchenjunga is in the Indian state of Sikkim. An independent Kingdom, it lies on the main route from India to Lhasa, which passes over the Nathu La pass into Tibet. East of Sikkim lies the ancient Buddhist Kingdom of Bhutan; the highest mountain in Bhutan is Gangkhar Puensum, a strong candidate for the highest unclimbed mountain in the world. The Himalayas here are becoming rugged with forested steep valleys; the Himalayas continue, turning northeast, through the Indian State of Arunachal Pradesh as well as Tibet, before reaching their easterly conclusion in the peak of Namche Barwa, situated in Tibet inside the great bend of the Yarlang Tsangpo river.
On the other side of the Tsangpo, to the east, are the Kangri Garpo mountains. The high mountains to the north of the Tsangpo including Gyala Peri, are sometimes included in the Himalayas. Going west from Dhaulagiri, Western Nepal is somewhat remote and lacks major high mountains, but is home to Rara Lake, the largest lake in Nepal; the Karnali River cuts through the center of the region. Further west, the border with India follows the Sarda River and provides a trade route into China, where on the Tibetan plateau lies the high peak of Gurla Mandhata. Just across Lake Manasarovar from this lies the sacred Mount Kailash, which stands close to the source of the four main rivers of Himalayas and is revered in Hinduism, Sufism and Bonpo. In the newly created Indian state of Uttarkhand, the Himalayas rise again as the Garhwal Himalayas with the high peaks of Nanda Devi and Kamet; the state is an important pilgrimage destination, with
The Mendip Hills is a range of limestone hills to the south of Bristol and Bath in Somerset, England. Running east to west between Weston-super-Mare and Frome, the hills overlook the Somerset Levels to the south and the Chew Valley and other tributaries of the Avon to the north; the hills give their name to the local government district of Mendip, which administers most of the area. The higher, western part of the hills, covering 198 km2 has been designated an Area of Outstanding Natural Beauty, which gives it a level of protection comparable to a national park; the hills are formed from Carboniferous Limestone, quarried at several sites. Three nationally important semi-natural habitats are characteristic of the area: ash–maple woodland, calcareous grassland and mesotrophic grassland. With their temperate climate these support a range of flora and fauna including birds and small mammals; the dry stone walls that divide the pasture into fields are of botanical importance as they support important populations of the nationally scarce wall whitlowgrass.
The origin of the name "Mendip" is unclear, but it is known that there has been human habitation since Palaeolithic and Mesolithic times with a range of artefacts being recovered from caves. Neolithic, Iron Age, Bronze Age features such as barrows are numerous with over 200 scheduled ancient monuments recorded. There is evidence of mining in the Mendips dating back to the late Bronze Age, which increased after the Roman invasion for lead and silver around Charterhouse; the difficult conditions in the area were noted by William Wilberforce in 1789, which inspired Hannah More to begin her work improving the conditions of the Mendip miners and agricultural workers. In the 18th and early 19th centuries 7,300 ha of the common heathland on the hills were enclosed. In World War II a bombing decoy was constructed on top of Black Down at Beacon Batch. More the mast of the Mendip transmitting station, micro-hydroelectric turbines and a wind turbine have been installed. There are still several quarries on the Mendip Hills.
Some of the stone is still carried by Mendip Rail. Although the Roman Fosse Way crossed the hills, the main roads avoid the higher areas and run along the bottom of the scarp slope on the north and south of the hills; the western end of the hills is crossed by the M5 motorway and A38. Further east, running north to south, are the A37 and A39. A wide range of outdoor sports and leisure activities take place in the Mendips, many based on the particular geology of the area; the hills are recognised as a national centre for caving and cave diving, as well as being popular with climbers and natural historians. Wookey Hole Caves and some of the caves in Cheddar Gorge are open as show caves. Long distance footpaths include the Mendip Limestone Link. Several explanations for the name "Mendip" have been suggested, its earliest known form is Mendepe in 1185. One suggestion is that it is derived from the medieval term "Myne-deepes". Others suggest it derives from Celtic monith, meaning mountain or hill, with an uncertain second element Old English yppe in the sense of upland or plateau.
A third explanation is. The suffix may be a contraction of the Old English hop. Possible further meanings have been identified; the first is'the stone pit' from the Celtic meyn and dyppa in reference to the collapsed cave systems of Cheddar. The second is "awesome" from the Old English moen and deop; the Mendip Hills are the most southerly Carboniferous Limestone upland in Britain. The rock strata known as the Carboniferous Limestone were laid down during the early Carboniferous Period, about 320–350 million years ago. Subsequently, much of northwestern Europe underwent continental collision throughout the late Paleozoic Era, culminating in the final phases of the Variscan orogeny near the end of the Carboniferous, 300 million years ago; this tectonic activity produced a complex suite of mountain and hill ranges across what is now southern Ireland, south-western England and elsewhere in western Europe. As a result of the Variscan mountain-building, the Mendip area now comprises at least four anticlinal fold structures, with an east-west trend, each with a core of older Devonian sandstone and Silurian volcanic rocks.
The latter are quarried as a concrete aggregate. The Mendips were higher and steeper 200 to 300 million years ago, subsequent erosion has resulted in a range of surface features including gorges, dry valleys, screes and others typical of karst landscapes; these are complemented underground by a large number of caves both beneath the plateau and at the base of the southern escarpment. Wookey Hole is one example of the caves of the area. There are areas of limestone pavement and other karst features. Dissolution of the limestone produced many of the gorges including Cheddar Gorge and Burrington Combe. Springs are a common feature of the eastern part of the hills, a number of which have associated tufa deposits; the Devonian and Silurian rocks are more resistant to weathering than the limestone, form some of the highest points on the hills, including the highest at Beacon Batch on Black Down, 325 metres above sea level. Black Down is a moorland area, with its steeper slopes covered in bracken and its flatter summit in heather and grasses rather than the pasture which covers much of the plate
Yorkshire, formally known as the County of York, is a historic county of Northern England and the largest in the United Kingdom. Due to its great size in comparison to other English counties, functions have been undertaken over time by its subdivisions, which have been subject to periodic reform. Throughout these changes, Yorkshire has continued to be recognised as a geographical territory and cultural region; the name is familiar and well understood across the United Kingdom and is in common use in the media and the military, features in the titles of current areas of civil administration such as North Yorkshire, South Yorkshire, West Yorkshire and East Riding of Yorkshire. Within the borders of the historic county of Yorkshire are vast stretches of unspoiled countryside; this can be found in the Yorkshire Dales and North York Moors and with the open aspect of some of the major cities. Yorkshire has been named "God's Own County" or "God's Own Country"; the emblem of Yorkshire is the White Rose of the English royal House of York, the most used flag representative of Yorkshire is the White Rose on a blue background, which after nearly fifty years of use, was recognised by the Flag Institute on 29 July 2008.
Yorkshire Day, held annually on 1 August, is a celebration of the general culture of Yorkshire, ranging from its history to its own dialect. Yorkshire is covered by different Government Office Regions. Most of the county falls within Yorkshire and the Humber while the extreme northern part of the county, such as Middlesbrough, Redcar and Startforth, falls within North East England. Small areas in the west of the county are covered by the North West England region. Yorkshire or the County of York was so named as it is the shire of York's Shire. "York" comes from the Viking name for Jórvík. "Shire" is from scir meaning care or official charge. The "shire" suffix is locally pronounced /-ʃə/ "shuh", or /-ʃiə/, a homophone of "sheer". Early inhabitants of Yorkshire were Celts, who formed two separate tribes, the Brigantes and the Parisi; the Brigantes controlled territory which became all of the North Riding of Yorkshire and the West Riding of Yorkshire. The tribe controlled most of Northern England and more territory than any other Celtic tribe in England.
That they had the Yorkshire area as their heartland is evident in that Isurium Brigantum was the capital town of their civitas under Roman rule. Six of the nine Brigantian poleis described by Claudius Ptolemaeus in the Geographia fall within the historic county; the Parisi, who controlled the area that would become the East Riding of Yorkshire, might have been related to the Parisii of Lutetia Parisiorum, Gaul. Their capital was at Petuaria, close to the Humber Estuary. Although the Roman conquest of Britain began in 43 AD, the Brigantes remained in control of their kingdom as a client state of Rome for an extended period, reigned over by the Brigantian monarchs Cartimandua and her husband Venutius; this situation suited both the Romans and the Brigantes, who were known as the most militant tribe in Britain. Queen Cartimandua left her husband Venutius for his armour bearer, setting off a chain of events which changed control of the region. Cartimandua, due to her good relationship with the Romans, was able to keep control of the kingdom.
At the second attempt, Venutius seized the kingdom, but the Romans, under general Petillius Cerialis, conquered the Brigantes in 71 AD. The fortified city of Eboracum was named as capital of Britannia Inferior and joint capital of all Roman Britain; the emperor Septimius Severus ruled the Roman Empire from Eboracum for the two years before his death. Another emperor, Constantius Chlorus, died in Eboracum during a visit in 306 AD; this saw his son Constantine the Great, who became renowned for his contributions to Christianity, proclaimed emperor in the city. In the early 5th century, the Roman rule ceased with the withdrawal of the last active Roman troops. By this stage, the Western Empire was in intermittent decline. After the Romans left, small Celtic kingdoms arose in the region, including the Kingdom of Ebrauc around York and the Kingdom of Elmet to the west. Elmet remained independent from the Germanic Northumbrian Angles until some time in the early 7th century, when King Edwin of Northumbria expelled its last king and annexed the region.
At its greatest extent, Northumbria stretched from the Irish Sea to the North Sea and from Edinburgh down to Hallamshire in the south. Scandinavian York or Danish/Norwegian York is a term used by historians for the south of Northumbria during the period of the late 9th century and first half of the 10th century, when it was dominated by Norse warrior-kings. Norse monarchy controlled varying amounts of Northumbria from 875 to 954, however the area was invaded and conquered for short periods by England between 927 and 954 before being annexed into England in 954, it was associated with the much longer-lived Kingdom of Dublin throughout this period. An army of Danish Vikings, the Great Heathen Army as its enemies referred to it, invaded Northumbrian territory in 866 AD; the Danes conquered and assumed what is now York and renamed it Jórvík, making it the capital city of a new Danish kingdom under the same name. The area which this kingdom covered included most of Southern Northumbria equivalent to the borders of Yorkshire extending further West.
The Danes went on to conque
Sediment is a occurring material, broken down by processes of weathering and erosion, is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation and if buried, may become sandstone and siltstone. Sediments are most transported by water, but wind and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian deposition. Glacial moraine deposits and till are ice-transported sediments. Sediment can be classified based on its grain composition. Sediment size is measured on a log base 2 scale, called the "Phi" scale, which classifies particles by size from "colloid" to "boulder". Composition of sediment can be measured in terms of: parent rock lithology mineral composition chemical make-up.
This leads to an ambiguity in which clay can be used as a composition. Sediment is transported based on the strength of the flow that carries it and its own size, volume and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, while larger or denser particles will be more to fall through the flow. Rivers and streams carry sediment in their flows; this sediment can be in a variety of locations within the flow, depending on the balance between the upwards velocity on the particle, the settling velocity of the particle. These relationships are shown in the following table for the Rouse number, a ratio of sediment fall velocity to upwards velocity. Rouse = Settling velocity Upwards velocity from lift and drag = w s κ u ∗ where w s is the fall velocity κ is the von Kármán constant u ∗ is the shear velocity If the upwards velocity is equal to the settling velocity, sediment will be transported downstream as suspended load. If the upwards velocity is much less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling and saltating.
If the upwards velocity is higher than the settling velocity, the sediment will be transported high in the flow as wash load. As there are a range of different particle sizes in the flow, it is common for material of different sizes to move through all areas of the flow for given stream conditions. Sediment motion can create self-organized structures such as ripples, dunes, or antidunes on the river or stream bed; these bedforms are preserved in sedimentary rocks and can be used to estimate the direction and magnitude of the flow that deposited the sediment. Overland flow can transport them downslope; the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion. If overland flow is directly responsible for sediment entrainment but does not form gullies, it is called "sheet erosion". If the flow and the substrate permit channelization, gullies may form.
The major fluvial environments for deposition of sediments include: Deltas Point bars Alluvial fans Braided rivers Oxbow lakes Levees Waterfalls Wind results in the transportation of fine sediment and the formation of sand dune fields and soils from airborne dust. Glaciers carry a wide range of sediment sizes, deposit it in moraines; the overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation. This expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow; this equation is important in that changes in the power of the flow change the ability of the flow to carry sediment, this is reflected in the patterns of erosion and deposition observed throughout a stream. This can be localized, due to small obstacles. Erosion and deposition can be regional. Deposition can occur due to dam emplacement that causes the river to pool and deposit its entire load, or due to base level rise.
Seas and lakes accumulate sediment over time. The sediment can consist of terrigenous material, which originates on land, but may be deposited in either terrestrial, marine, or lacustrine environments, or of sediments originating in the body of water. Terrigenous material is supplied by nearby rivers and streams or reworked marine sediment. In the mid-ocean, the exoskeletons of dead organisms are responsible for sediment accumulation. Deposited sediments are the source of sedimentary rocks, which can contain fossils of
Yosemite Valley is a glacial valley in Yosemite National Park in the western Sierra Nevada mountains of Central California. The valley is about 7.5 miles long and 3000–3500 feet deep, surrounded by high granite summits such as Half Dome and El Capitan, densely forested with pines. The valley is drained by the Merced River, a multitude of streams and waterfalls flow into it, including Tenaya, Illilouette and Bridalveil Creeks. Yosemite Falls is the highest waterfall in North America, is a big attraction in the spring when the water flow is at its peak; the valley is renowned for its natural environment, is regarded as the centerpiece of Yosemite National Park, attracting visitors from around the world. The Valley is the main attraction in the park for the majority of visitors, a bustling hub of activity during tourist season in the summer months. Most visitors pass through the Tunnel View entrance. Visitor facilities are located in the center of the valley. There are both hiking trail loops that stay within the valley and trailheads that lead to higher elevations, all of which afford glimpses of the park's many scenic wonders.
Yosemite Valley is located on the western slope of the Sierra Nevada mountains, 150 miles due east of San Francisco. It stretches for 7.5 miles in a east–west direction, with an average width of about 1 mile. Yosemite Valley represents only one percent of the park area, but this is where most visitors arrive and stay. More than half a dozen creeks tumble from hanging valleys at the top of granite cliffs that can rise 3000–3500 feet above the valley floor, which itself is 4000 ft above sea level; these streams combine into the Merced River, which flows out from the western end of the valley, down the rest of its canyon to the San Joaquin Valley. The flat floor of Yosemite Valley holds both forest and large open meadows, which have views of the surrounding crests and waterfalls. Below is a description of these features, looking first at the walls above, moving west to east as a visitor does when entering the valley visiting the waterfalls and other water features, returning east to west with the flow of water.
The first view of Yosemite Valley many visitors see is the Tunnel View. So many paintings were made from a viewpoint nearby that the National Park Service named that viewpoint Artist Point; the view from the lower end of the Valley contains the great granite monolith El Capitan on the left, Cathedral Rocks on the right with Bridalveil Fall. Just past this spot the Valley widens with the Cathedral Spires the pointed obelisk of Sentinel Rock to the south. Across the Valley on the northern side are the Three Brothers, rising one above the other like gables built on the same angle – the highest crest is Eagle Peak, with the two below known as the Middle and Lower Brothers. To this point the Valley has been curving to the left. Now a grand curve back to the right begins, with Yosemite Falls on the north, followed by the Royal Arches, topped by North Dome. Opposite, to the south, is Glacier Point, 3,200 feet above the Valley floor. At this point the Valley splits in two, one section slanting northeast, with the other curving from south to southeast.
Between them, at the eastern end of the valley, is Half Dome, among the most prominent natural features in the Sierra Nevada. Above and to the northeast of Half Dome is Clouds Rest. Snow melting in the Sierra forms lakes. In the surrounding region, these creeks flow to the edge of the Valley to form cataracts and waterfalls. A fan of creeks and forks of the Merced River take drainage from the Sierra crest and combine at Merced Lake; the Merced flows down to the end of its canyon, where it begins what is called the Giant Staircase. The first drop is Nevada Fall. Below is one of the most picturesque waterfalls in the Valley; the Merced descends rapids to meet Illilouette Creek, which drops from the valley rim to form Illilouette Fall. They combine at the base of the gorges that contain each stream, flow around the Happy Isles to meet Tenaya Creek at the eastern end of Yosemite Valley proper. Tenaya Creek flows southwest from Tenaya Lake and down Tenaya Canyon flowing between Half Dome and North Dome before joining the Merced River.
The following falls tumble from the Valley rim to join it at various points: Yosemite Falls 2,425 feet Upper Yosemite Fall 1,430 feet, the middle cascades 670 feet, Lower Yosemite Fall 320 feet. Snow Creek Falls 2,140 feet Sentinel Falls 1,920 feet Ribbon Fall 1,612 feet Royal Arch Cascade 1,250 feet Lehamite Falls 1,180 feet Staircase Falls 1,020 feet Bridalveil Fall 620 feet. Nevada Fall 594 feet Silver Strand Falls 574 feet Vernal Fall 318 feet The features in Yosemite Valley are made of granitic rock emplaced as plutons miles deep during the late Cretaceous. Over time the Sierra Nevada was uplifted; the oldest of these granitic rocks, at 114 million years, occur along the Merced River Gorge west of the valley. The El Capitan pluton intruded the valley, forming most of the granitic rock that makes up much of the central part of the valley, including Cathedral Rocks, Three Brothers, El Capitan; the youngest Yosemite Valley pluton is the 87-million-year-old Half Dome granodiorite, which makes up most of the rock at