An oxbow lake is a U-shaped lake that forms when a wide meander from the main stem of a river is cut off, creating a free-standing body of water. This landform is so named for its distinctive curved shape. In Australia, an oxbow lake is called a billabong, from the indigenous Wiradjuri language. In south Texas, oxbows left by the Rio Grande are called resacas; the word "oxbow" can refer to a U-shaped bend in a river or stream, whether or not it is cut off from the main stream. An oxbow lake forms. After a long period of time, the meander becomes curved, the neck of the meander becomes narrower and the river cuts through the neck during a flood, cutting off the meander and forming an oxbow lake; when a river reaches a low-lying plain in its final course to the sea or a lake, it meanders widely. In the vicinity of a river bend, deposition occurs on the convex bank. In contrast, both lateral erosion and undercutting occur on the cut bank or concave bank Continuous deposition on the convex bank and erosion of the concave bank of a meandering river cause the formation of a pronounced meander with two concave banks getting closer.
The narrow neck of land between the two neighboring concave banks is cut through, either by lateral erosion of the two concave banks or by the strong currents of a flood. When this happens a new, straighter river channel develops—and an abandoned meander loop, called a cutoff, forms; when deposition seals off the cutoff from the river channel, an oxbow lake forms. This process can occur over a time from a few years to several decades, may sometimes become static. Gathering of erosion products near the concave bank and transporting them to the convex bank is the work of the secondary flow across the floor of the river in the vicinity of a river bend; the process of deposition of silt and gravel on the convex bank is illustrated in point bars. River flood plains that contain rivers with a sinuous platform are populated by longer oxbow lakes than those with low sinuosity; this is because rivers with high sinuosity have larger meanders, greater opportunity for longer lakes to form. Rivers with lower sinuosity are characterized by fewer cutoffs and shorter oxbow lakes due to the shorter distance of their meanders.
The effect of the secondary flow can be demonstrated using a circular bowl. Fill the bowl with water and sprinkle dense particles such as sand or rice into the bowl. Set the water into circular motion with one hand or a spoon; the dense particles sweep into a neat pile in the center of the bowl. This is the mechanism that leads to the formation of point bars and contributes to the formation of oxbow lakes; the primary flow of water in the bowl is circular and the streamlines are concentric with the side of the bowl. However, the secondary flow of the boundary layer across the floor of the bowl is inward toward the center; the primary flow might be expected to fling the dense particles to the perimeter of the bowl, but instead the secondary flow sweeps the particles toward the center. The curved path of a river around a bend makes the water's surface higher on the outside of the bend than on the inside; as a result, at any elevation within the river, water pressure is greater near the outside of the bend than on the inside.
A pressure gradient toward the convex bank provides the centripetal force necessary for each parcel of water to follow its curved path. The boundary layer that flows along the river floor does not move fast enough to balance the pressure gradient laterally across the river, it responds to this pressure gradient, its velocity is downstream and across the river toward the convex bank. As it flows along the floor of the river, it sweeps loose material toward the convex bank; this flow of the boundary layer is different from the speed and direction of the primary flow of the river, is part of the river's secondary flow. When a fluid follows a curved path, such as around a circular bowl, around a bend in a river or in a tropical cyclone, the flow is described as vortex flow: the fastest speed occurs where the radius is smallest, the slowest speed occurs where the radius is greatest; the higher fluid pressure and slower speed where the radius is greater, the lower pressure and faster speed where the radius is smaller, are all consistent with Bernoulli's principle.
Notable examples Bole and Burton Round in West Burton, England are a good example of previous lakes in a close proximity to one another. Carter Lake, Iowa was created after severe flooding in 1877 led to the river shifting 1.25 mi to the southeast. Cuckmere Haven in Sussex, England contains a meandering river with many oxbow lakes referred to in physical geography textbooks. Half Moon Lake in downtown Eau Claire, Wisconsin was formed due to a shift in the course of the Chippewa River, which now flows to the south. Kanwar Lake Bird Sanctuary, India contains rare and endangered migratory birds and is one of Asia's largest oxbow lakes; the Oxbow, a 2.5-mile bend in the Connecticut River, is disconnected at one end. There are many oxbow lakes alongside its tributaries; the largest oxbow lake in North America, Lake Chicot, was part of the Mississippi River, as was Horseshoe Lake, the namesake for the town of Horseshoe Lake, Arkansas. Reelfoot Lake in west Tennessee is another notable oxbow lake. Oxbow lake
Cambridge University Press
Cambridge University Press is the publishing business of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the world's oldest publishing house and the second-largest university press in the world, it holds letters patent as the Queen's Printer. The press mission is "to further the University's mission by disseminating knowledge in the pursuit of education and research at the highest international levels of excellence". Cambridge University Press is a department of the University of Cambridge and is both an academic and educational publisher. With a global sales presence, publishing hubs, offices in more than 40 countries, it publishes over 50,000 titles by authors from over 100 countries, its publishing includes academic journals, reference works and English language teaching and learning publications. Cambridge University Press is a charitable enterprise that transfers part of its annual surplus back to the university. Cambridge University Press is both the oldest publishing house in the world and the oldest university press.
It originated from letters patent granted to the University of Cambridge by Henry VIII in 1534, has been producing books continuously since the first University Press book was printed. Cambridge is one of the two privileged presses. Authors published by Cambridge have included John Milton, William Harvey, Isaac Newton, Bertrand Russell, Stephen Hawking. University printing began in Cambridge when the first practising University Printer, Thomas Thomas, set up a printing house on the site of what became the Senate House lawn – a few yards from where the press's bookshop now stands. In those days, the Stationers' Company in London jealously guarded its monopoly of printing, which explains the delay between the date of the university's letters patent and the printing of the first book. In 1591, Thomas's successor, John Legate, printed the first Cambridge Bible, an octavo edition of the popular Geneva Bible; the London Stationers objected strenuously. The university's response was to point out the provision in its charter to print "all manner of books".
Thus began the press's tradition of publishing the Bible, a tradition that has endured for over four centuries, beginning with the Geneva Bible, continuing with the Authorized Version, the Revised Version, the New English Bible and the Revised English Bible. The restrictions and compromises forced upon Cambridge by the dispute with the London Stationers did not come to an end until the scholar Richard Bentley was given the power to set up a'new-style press' in 1696. In July 1697 the Duke of Somerset made a loan of £200 to the university "towards the printing house and presse" and James Halman, Registrary of the University, lent £100 for the same purpose, it was in Bentley's time, in 1698, that a body of senior scholars was appointed to be responsible to the university for the press's affairs. The Press Syndicate's publishing committee still meets and its role still includes the review and approval of the press's planned output. John Baskerville became University Printer in the mid-eighteenth century.
Baskerville's concern was the production of the finest possible books using his own type-design and printing techniques. Baskerville wrote, "The importance of the work demands all my attention. Caxton would have found nothing to surprise him if he had walked into the press's printing house in the eighteenth century: all the type was still being set by hand. A technological breakthrough was badly needed, it came when Lord Stanhope perfected the making of stereotype plates; this involved making a mould of the whole surface of a page of type and casting plates from that mould. The press was the first to use this technique, in 1805 produced the technically successful and much-reprinted Cambridge Stereotype Bible. By the 1850s the press was using steam-powered machine presses, employing two to three hundred people, occupying several buildings in the Silver Street and Mill Lane area, including the one that the press still occupies, the Pitt Building, built for the press and in honour of William Pitt the Younger.
Under the stewardship of C. J. Clay, University Printer from 1854 to 1882, the press increased the size and scale of its academic and educational publishing operation. An important factor in this increase was the inauguration of its list of schoolbooks. During Clay's administration, the press undertook a sizeable co-publishing venture with Oxford: the Revised Version of the Bible, begun in 1870 and completed in 1885, it was in this period as well that the Syndics of the press turned down what became the Oxford English Dictionary—a proposal for, brought to Cambridge by James Murray before he turned to Oxford. The appointment of R. T. Wright as Secretary of the Press Syndicate in 1892 marked the beginning of the press's development as a modern publishing business with a defined editorial policy and administrative structure, it was Wright who devised the plan for one of the most distinctive Cambridge contributions to publishing—the Cambridge Histories. The Cambridge Modern History was published
A river mouth is the part of a river where the river debouches into another river, a lake, a reservoir, a sea, or an ocean. The water from a river can enter the receiving body in a variety of different ways; the motion of a river is influenced by the relative density of the river compared to the receiving water, the rotation of the earth, any ambient motion in the receiving water, such as tides or seiches. If the river water has a higher density than the surface of the receiving water, the river water will plunge below the surface; the river water will either form an underflow or an interflow within the lake. However, if the river water is lighter than the receiving water, as is the case when fresh river water flows into the sea, the river water will float along the surface of the receiving water as an overflow. Alongside these advective transports, inflowing water will diffuse. At the mouth of a river, the change in flow condition can cause the river to drop any sediment it is carrying; this sediment deposition can generate a variety of landforms, such as deltas, sand bars and tie channels.
Many places in the United Kingdom take their names from their positions at the mouths of rivers, such as Plymouth and Great Yarmouth. Confluence River delta Estuary Liman
The Agoyán is the tallest waterfall of the Ecuadorian Andes. It is located 7 kilometres from the city of Baños, it is formed by the waters of the Pastaza River that plunge 61 metres in a gorge located in the Occidental Cordillera. In 1987, the Ecuadorian government inaugurated the Agoyán hydroelectric plant, part of the country's power grid since with a total power output of 156 MW; the plant was built upstream of the waterfall, so as to preserve it
Mera is a town in the eastern foothills of the Ecuadorian Andes. It is the name of the Canton in Pastaza Province of which it is a part, it lends its name to Shell Mera, a larger town 4 miles to the east. Aerial photograph of Mera
Shell Mera is a town located in the eastern foothills of the Ecuadorian Andes, about 94 miles from Quito. Its name comes from the Royal Dutch Shell Company, the smaller town of Mera, 5 miles to the northwest. Shell Mera was established in 1937 as a Shell Oil Company base, it consisted of little more than several basic shacks and a 5,000-foot airstrip. It was operated as part of Shell's prospecting efforts in the region; the base was located near some Indian tribes that opposed the exploitation of resources found in their ancestral territories. On a few occasions the Indians attacked Shell; the oil company considered the base too dangerous to maintain, abandoned it in 1948. However, it is more that business prospects had more to do with the decision, it was during this time that the Middle East rose in prominence in the oil industry, since it was becoming much more productive. After spending 10 years prospecting in Ecuador, the oil company had not produced any oil from the region. Sometime around 1949, Shell was reoccupied by Mission Aviation Fellowship.
MAF recognized the importance of Shell due to its road access to Quito. They used it as their main base of operations for mission work in Ecuador, it was the home base of MAF pilots Nate Saint and Johnny Keenan. In 1954 Saint, a former member of the U. S. Army, welcomed General James Doolittle to Shell. Doolittle was an Air Force aviator who rose to fame during what became known as "Doolittle's Raid" over Tokyo in 1942. General Doolittle was visiting Ecuador for then-President Eisenhower on a fact-finding mission for the CIA. World-wide attention focused on Shell in January 1956 at the news of the disappearance of Saint and four other missionaries – Jim Elliot, Pete Fleming, Ed McCully, Roger Youderian, they had been trying to reach the Huaorani tribe, had been making aerial reconnaissance missions. When they landed in Huaorani territory they were killed by the natives, their bodies thrown into the Curaray River. Once again, Shell served as a base of operations, this time for the families of the victims and rescue workers.
Two years in 1958, the Hospital Vozandes Del Oriente opened its doors as the first hospital in that region of Ecuador. The hospital was the dream of Nate Saint, who donated both land and time to work on its construction before his death in 1956, it served an estimated 65,000 people who lived in the jungle. In 1985 a new Hospital Vozandes was opened on the other side of the Motolo River, the old hospital was converted to a guest house, lasting until 2007 when weather and termites forced it to be torn down; the new Hospital Vozandes Del Oriente was closed at the end of 2013, after 55 years of service in Pastaza. In August 1964, Nate Saint Memorial School opened in Shell for missionary children; the school was founded by Charlotte Dillon Swanson wife of Wallace Swanson, a missionary physician at the HCJB Hospital Voz Andes. She began by teaching her own children at home in 1962 and expanded the school to include other missionary children. After she raised money for a building she named the school in memory of Nate Saint.
Today, Shell is a much larger town than it was, complete with a Spanish-speaking church, schools and missionary guest houses. The Saints' house is still standing. Hospital Basico del Oriente is being reopened by a team led by Dr. Eckehart Wolff and other physicians who are supporting this effort; the airstrip remains operational and continues to service the region as the Rio Amazonas Airport, owned by the military and used as a base. The airport is still a major base of operations for the MAF. Elliot, Through Gates of Splendor. Elliot, Philip James, Billy Graham Center, Collection 277. Hoffman, Shell-Mera, The Hoffman family. Maxwell, The Waorani New Testament Dedication Service, OSLC-GB. Wishall, Garrett E. Experiencing the culture firsthand Time Magazine article Rachel Saint History, The Akha Heritage Foundation, Feb 2006. Nate Saint Memorial School, HCJB. Rio Amazonas Airport, Private Jet Specialist. Aerial Pictures of Shell Mera, The Hoffman family. Hospital Vozandes in Shell, HCJB
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 6,300,000 km2, or about 35.5 percent that of the South American continent. It is located in the countries of Bolivia, Colombia, Guyana, Peru and Venezuela. Most of the basin is covered by the Amazon Rainforest known as Amazonia. With a 5,500,000 km2 area of dense tropical forest, this is the largest rainforest in the world; the Amazon River begins in the Andes Mountains at the west of the basin with its main tributary the Marañón River in Peru. The highest point in the watershed of the Amazon is the peak of Yerupajá at 6,635 metres. With a length of about 6,400 km before it drains into the Atlantic Ocean, it is one of the two longest rivers in the world; the Amazon system transports the largest volume of water of any river system, accounting for about 20% of the total water carried to the oceans by rivers. Some of the Amazon rainforests are deforested because of the increasing of cattle ranches and soy beans field.
The Amazon basin flowed west to Pacific Ocean until the Andes formed, causing the basin to flow eastward towards the Atlantic Ocean. Politically the basin is divided into the Brazilian Amazônia Legal, the Peruvian Amazon, the Amazon region of Colombia and parts of Bolivia and the Venezuelan state of Amazonas. Plant growth is dense and its variety of animal inhabitants is comparatively high due to the heavy rainfall and the dense and extensive evergreen and coniferous forests. Little sunlight reaches the ground due to the dense roof canopy by plants; the ground remains dark and damp and only shade tolerant vegetation will grow here. Orchids and bromeliads exploit other plants to get closer to the sunlight, they grow hanging onto the branches or tree trunks with aerial roots, not as parasites but as epiphytes. Species of tropical trees native to the Amazon include rubber tree and Assai palm. More than 1,400 species of mammals are found in the Amazon, the majority of which are species of bats and rodents.
Its larger mammals include the jaguar, ocelot and South American tapir. About 1500 bird species inhabit the Amazon Basin; the biodiversity of the Amazon and the sheer number of diverse bird species is given by the number of different bird families that reside in these humid forests. An example of such would be the cotinga family. Birds such as toucans, hummingbirds are found here. Macaws are famous for gathering by the hundreds along the clay cliffs of the Amazon River. In the western Amazon hundreds of macaws and other parrots descend to exposed river banks to consume clay on an daily basis, the exception being rainy days; the green anaconda inhabits the shallow waters of the Amazon and the emerald tree boa and boa constrictor live in the Amazonian tree tops. Many reptiles species are illegally exported for the international pet trade. Live animals are the fourth largest commodity in the smuggling industry after drugs and weapons. More than 1,500 species of amphibians are found in the Amazon. Unlike temperate frogs which are limited to habitats near the water, tropical frogs are most abundant in the trees and few are found near bodies of water on the forest floor.
The reason for this occurrence is quite simple: frogs must always keep their skin moist since half of their respiration is carried out through their skin. The high humidity of the rainforest and frequent rainstorms gives tropical frogs infinitely more freedom to move into the trees and escape the many predators of rainforest waters; the differences between temperate and tropical frogs extend beyond their habitat. About 2,500 fish species are known from the Amazon basin and it is estimated that more than 1,000 additional undescribed species exist; this is more than any other river basin on Earth, Amazonia is the center of diversity for Neotropical fishes. About 45% of the known Amazonian fish species are endemic to the basin; the remarkable species richness can in part be explained by the large differences between the various parts of the Amazon basin, resulting in many fish species that are endemic to small regions. For example, fauna in clearwater rivers differs from fauna in white and blackwater rivers, fauna in slow moving sections show distinct differences compared to that in rapids, fauna in small streams differ from that in major rivers, fauna in shallow sections show distinct differences compared to that in deep parts.
By far the most diverse orders in the Amazon are Characiformes and Siluriformes, but other groups with many species include Cichlidae and Gymnotiformes. In addition to major differences in behavior and ecology, Amazonian fish vary extensively in form and size; the largest, the arapaima and piraiba can reach 3 m or more in length and up to 200 kg in weight, making them some of the largest strict freshwater fish in the world. The bull shark and common sawfish, which have been recorded far up the Amazon, may reach greater sizes, but they are euryhaline and seen in marine waters. In contrast to the giants, there are Amazonian fish from several families that are less than 2 cm long; the smallest are the Leptophilypnion sleeper gobies, which do not surpass 1 cm and are among the smallest fish in the world. The Amazon supports large fisheries, including well-known species of large catfish (such as Brachyplatystoma, which perform l