Oceanography known as oceanology, is the study of the physical and biological aspects of the ocean. It is an important Earth science, which covers a wide range including ecosystem dynamics; these diverse topics reflect multiple disciplines that oceanographers blend to further knowledge of the world ocean and understanding of processes within: astronomy, chemistry, geography, hydrology and physics. Paleoceanography studies the history of the oceans in the geologic past. Humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations on tides were recorded by Strabo. Early exploration of the oceans was for cartography and limited to its surfaces and of the animals that fishermen brought up in nets, though depth soundings by lead line were taken. Although Juan Ponce de León in 1513 first identified the Gulf Stream, the current was well known to mariners, Benjamin Franklin made the first scientific study of it and gave it its name. Franklin measured water temperatures during several Atlantic crossings and explained the Gulf Stream's cause.
Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769–1770. Information on the currents of the Pacific Ocean was gathered by explorers of the late 18th century, including James Cook and Louis Antoine de Bougainville. James Rennell wrote the first scientific textbooks on oceanography, detailing the current flows of the Atlantic and Indian oceans. During a voyage around the Cape of Good Hope in 1777, he mapped "the banks and currents at the Lagullas", he was the first to understand the nature of the intermittent current near the Isles of Scilly. Sir James Clark Ross took the first modern sounding in deep sea in 1840, Charles Darwin published a paper on reefs and the formation of atolls as a result of the second voyage of HMS Beagle in 1831–1836. Robert FitzRoy published a four-volume report of Beagle's three voyages. In 1841 -- 1842 Edward Forbes undertook dredging in the Aegean Sea; the first superintendent of the United States Naval Observatory, Matthew Fontaine Maury devoted his time to the study of marine meteorology and charting prevailing winds and currents.
His 1855 textbook Physical Geography of the Sea was one of the first comprehensive oceanography studies. Many nations sent oceanographic observations to Maury at the Naval Observatory, where he and his colleagues evaluated the information and distributed the results worldwide. Despite all this, human knowledge of the oceans remained confined to the topmost few fathoms of the water and a small amount of the bottom in shallow areas. Nothing was known of the ocean depths; the British Royal Navy's efforts to chart all of the world's coastlines in the mid-19th century reinforced the vague idea that most of the ocean was deep, although little more was known. As exploration ignited both popular and scientific interest in the polar regions and Africa, so too did the mysteries of the unexplored oceans; the seminal event in the founding of the modern science of oceanography was the 1872–1876 Challenger expedition. As the first true oceanographic cruise, this expedition laid the groundwork for an entire academic and research discipline.
In response to a recommendation from the Royal Society, the British Government announced in 1871 an expedition to explore world's oceans and conduct appropriate scientific investigation. Charles Wyville Thompson and Sir John Murray launched the Challenger expedition. Challenger, leased from the Royal Navy, was modified for scientific work and equipped with separate laboratories for natural history and chemistry. Under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical miles surveying and exploring. On her journey circumnavigating the globe, 492 deep sea soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature observations were taken. Around 4,700 new species of marine life were discovered; the result was the Report Of The Scientific Results of the Exploring Voyage of H. M. S. Challenger during the years 1873–76. Murray, who supervised the publication, described the report as "the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries".
He went on to found the academic discipline of oceanography at the University of Edinburgh, which remained the centre for oceanographic research well into the 20th century. Murray was the first to study marine trenches and in particular the Mid-Atlantic Ridge, map the sedimentary deposits in the oceans, he tried to map out the world's ocean currents based on salinity and temperature observations, was the first to understand the nature of coral reef development. In the late 19th century, other Western nations sent out scientific expeditions; the first purpose built oceanographic ship, was built in 1882. In 1893, Fridtjof Nansen allowed Fram, to be frozen in the Arctic ice; this enabled him to obtain oceanographic and astronomical data at a stationary spot over an extended period. In 1881 the geographer John Francon Williams published Geography of the Oceans. Between 1907 and 1911 Otto Krümmel published the Handbuch der Ozeanographie, which became influential in awakening public interest in oceanography.
Pelagic sediment or pelagite is a fine-grained sediment that accumulates as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton. Trace amounts of meteoric dust and variable amounts of volcanic ash occur within pelagic sediments. Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, red clays; the composition of pelagic sediments is controlled by three main factors. The first factor is the distance from major landmasses, which affects their dilution by terrigenous, or land-derived, sediment; the second factor is water depth, which affects the preservation of both siliceous and calcareous biogenic particles as they settle to the ocean bottom. The final factor is ocean fertility, which controls the amount of biogenic particles produced in surface waters. In case of marine sediments, ooze does not refer to a sediment's consistency, but to its composition, which directly reflects its origin.
Ooze is pelagic sediment that consists of at least 30% of microscopic remains of either calcareous or siliceous planktonic debris organisms. The remainder consists entirely of clay minerals; as a result, the grain size of oozes is bimodal with a well-defined biogenic silt- to sand-size fraction and siliciclastic clay-size fraction. Oozes can be classified according to the predominate organism that compose them. For example, there are diatom, foraminifera, globigerina and radiolarian oozes. Oozes are classified and named according to their mineralogy, i.e. calcareous or siliceous oozes. Whatever their composition, all oozes accumulate slowly, at no more than a few centimeters per millennium. Calcareous ooze is ooze, composed of at least 30% of the calcareous microscopic shells—also known as tests—of foraminifera and pteropods; this is the most common pelagic sediment by area, covering 48% of the world ocean's floor. This type of ooze accumulates on the ocean floor at depths above the carbonate compensation depth.
It accumulates more than any other pelagic sediment type, with a rate that varies from 0.3–5 cm/1000 yr. Siliceous ooze is ooze, composed of at least 30% of the siliceous microscopic "shells" of plankton, such as diatoms and radiolaria. Siliceous oozes contain lesser proportions of either sponge spicules, silicoflagellates or both; this type of ooze accumulates on the ocean floor at depths below the carbonate compensation depth. Its distribution is limited to areas with high biological productivity, such as the polar oceans, upwelling zones near the equator; the least common type of sediment, it covers only 15% of the ocean floor. It accumulates at a slower rate than calcareous ooze: 0.2–1 cm/1000 yr. Red clay known as either brown clay or pelagic clay, accumulates in the deepest and most remote areas of the ocean, it covers 38% of the ocean floor and accumulates more than any other sediment type, at only 0.1–0.5 cm/1000 yr. Containing less than 30% biogenic material, it consists of sediment that remains after the dissolution of both calcareous and siliceous biogenic particles while they settled through the water column.
These sediments consist of aeolian quartz, clay minerals, volcanic ash, subordinate residue of siliceous microfossils, authigenic minerals such as zeolites and manganese oxides. The bulk of red clay consists of eolian dust. Accessory constituents found in red clay include meteorite dust, fish bones and teeth, whale ear bones, manganese micro-nodules; these pelagic sediments are bright red to chocolate brown in color. The color results from coatings of manganese oxide on the sediment particles. In the absence of organic carbon and manganese remain in their oxidized states and these clays remain brown after burial; when more buried, brown clay may change into red clay due to the conversion of iron-hydroxides to hematite. These sediments accumulate on the ocean floor within areas characterized by little planktonic production; the clays which comprise them were transported into the deep ocean in suspension, either in the air over the oceans or in surface waters. Both wind and ocean currents transported these sediments in suspension thousands of kilometers from their terrestrial source.
As they were transported, the finer clays may have stayed in suspension for a hundred years or more within the water column before they settled to the ocean bottom. The settling of this clay-size sediment occurred by the formation of clay aggregates by flocculation and by their incorporation into fecal pellets by pelagic organisms. Chalk Diatomaceous earth Marine geology Petrological Database of the Ocean Floor Radiolarite SedDB, online database for sediment geochemistry http://www.odp.usyd.edu.au Total Sediment Thickness of the World's Oceans and Marginal Seas, Version 2
Sand is a granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than coarser than silt. Sand can refer to a textural class of soil or soil type; the composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica in the form of quartz. The second most common type of sand is calcium carbonate, for example, created, over the past half billion years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Sand is a non-renewable resource over human timescales, sand suitable for making concrete is in high demand. Desert sand, although plentiful, is not suitable for concrete, 50 billion tons of beach sand and fossil sand is needed each year for construction; the exact definition of sand varies.
The scientific Unified Soil Classification System used in engineering and geology corresponds to US Standard Sieves, defines sand as particles with a diameter of between 0.074 and 4.75 millimeters. By another definition, in terms of particle size as used by geologists, sand particles range in diameter from 0.0625 mm to 2 mm. An individual particle in this range size is termed a sand grain. Sand grains are between silt; the size specification between sand and gravel has remained constant for more than a century, but particle diameters as small as 0.02 mm were considered sand under the Albert Atterberg standard in use during the early 20th century. The grains of sand in Archimedes Sand Reckoner written around 240 BCE, were 0.02 mm in diameter. A 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A 1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers.
Silt, by comparison, feels like flour). ISO 14688 grades sands as fine and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is divided into five sub-categories based on size: fine sand, fine sand, medium sand, coarse sand, coarse sand; these sizes are based on the Krumbein phi scale, where size in Φ = -log2D. On this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers; the most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica in the form of quartz, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering. The composition of mineral sand is variable, depending on the local rock sources and conditions; the bright white sands found in tropical and subtropical coastal settings are eroded limestone and may contain coral and shell fragments in addition to other organic or organically derived fragmental material, suggesting sand formation depends on living organisms, too.
The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, white color. Arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop; some sands contain magnetite, glauconite or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian. Chlorite-glauconite bearing sands are green in color, as are sands derived from basaltic lava with a high olivine content. Many sands those found extensively in Southern Europe, have iron impurities within the quartz crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones. Rocks erode/weather over a long period of time by water and wind, their sediments are transported downstream; these sediments continue to break apart into smaller pieces. The type of rock the sediment originated from and the intensity of the environment gives different compositions of sand.
The most common rock to form sand is Granite, where the Feldspar minerals dissolve faster than the Quartz, causing the rock to break apart into small pieces. In high energy environments rocks break apart much faster than in more calm settings. For example, Granite rocks this means more Feldspar minerals in the sand because it wouldn't have had time to dissolve; the term for sand formed by weathering is epiclastic. Sand from rivers are collected either from the river itself or its flood plain, accounts for the majority of the sand used in the construction industry; because if this, many small rivers have been depleted, causing environmental concern and economic losses to adjacent land. The rate of sand mining in such areas outweighs the rate the sand can replenish, making it a non-renewable resource. Sand dunes are a consequence of wind deposition; the Sahara Desert is dry because of its geographic location and is known for its vast sand dunes. They exist here because little vegetation is able to grow and there's not a lot of water.
Over time, wind blow
A river is a natural flowing watercourse freshwater, flowing towards an ocean, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, brook and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location. Sometimes a river is defined as being larger than a creek, but not always: the language is vague. Rivers are part of the hydrological cycle. Potamology is the scientific study of rivers, while limnology is the study of inland waters in general. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, as a means of disposing of waste.
A river begins at a source, follows a path called a course, ends at a mouth or mouths. The water in a river is confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be wide in relation to the size of the river channel; this distinction between river channel and floodplain can be blurred in urban areas where the floodplain of a river channel can become developed by housing and industry. Rivers can flow down mountains, through valleys or along plains, can create canyons or gorges; the term upriver refers to the direction towards the source of the river, i.e. against the direction of flow. The term downriver describes the direction towards the mouth of the river, in which the current flows; the term left bank refers to the left bank in the direction of right bank to the right. The river channel contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river.
Extensive braided rivers are now found in only a few regions worldwide, such as the South Island of New Zealand. They occur on peneplains and some of the larger river deltas. Anastamosing rivers are quite rare, they have multiple sinuous channels carrying large volumes of sediment. There are rare cases of river bifurcation in which a river divides and the resultant flows ending in different seas. An example is the bifurcation of Nerodime River in Kosovo. A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. In 1757, the German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed; this formulation is sometimes called Airy's law. Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks.
A river valley, created from a U-shaped glaciated valley, can easily be identified by the V-shaped channel that it has carved. In the middle reaches where a river flows over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form estuaries. Throughout the course of the river, the total volume of water transported downstream will be a combination of the free water flow together with a substantial volume flowing through sub-surface rocks and gravels that underlie the river and its floodplain. For many rivers in large valleys, this unseen component of flow may exceed the visible flow. Most but not all rivers flow on the surface. Subterranean rivers flow underground in caverns; such rivers are found in regions with limestone geologic formations.
Subglacial streams are the braided rivers that flow at the beds of glaciers and ice sheets, permitting meltwater to be discharged at the front of the glacier. Because of the gradient in pressure due to the overlying weight of the glacier, such streams can flow uphill. An intermittent river only flows and can be dry for several years at a time; these rivers are found in regions with limited or variable rainfall, or can occur because of geologic conditions such as a permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter; such rivers are fed from chalk aquifers which recharge from winter rainfall. In England these rivers are called bournes and give their name to places such as Bournemouth and Eastbourne. In humid regions, the location where flow begins in the smallest tributary streams moves upstream in response to precipitation and downstream in its absence or when active summer vegetation diverts water for evapotrans
Mud is a liquid or semi-liquid mixture of water and any combination of different kinds of soil. It forms after rainfall or near water sources. Ancient mud deposits harden over geological time to form sedimentary rock such as mudstone; when geological deposits of mud are formed in estuaries, the resultant layers are termed bay muds. In the construction industry, mud is a semi-fluid material that can be used to coat, seal, or adhere materials. Depending on the composition of the mud, it can be referred by many different names, including slurry, plaster and concrete. Mud, adobe and many other names are used synonymously to mean a mixture of subsoil and water with the addition of stones, straw, and/or bitumen; this material was used a variety of ways to build walls and roofs. For thousands of years it was common in most parts of the world to build walls using mudbricks or the wattle and daub, rammed earth or cob techniques and cover the surfaces with earthen plaster. Mud can be made into mud bricks called adobe, by mixing mud with water, placing the mixture into moulds and allowing it to dry in open air.
Straw is sometimes used as a binder within the bricks. When the brick would otherwise break, the straw will redistribute the force throughout the brick, decreasing the chance of breakage; such buildings must be protected from groundwater by building upon a masonry, fired brick, rock or rubble foundation, from wind-driven rain in damp climates by deep roof overhangs. In dry climates a well drained flat roof may be protected with a well-prepared and properly maintained dried mud coating, viable as the mud will expand when moistened and so become more water resistant. Adobe mudbricks were used by the Pueblo Indians to build their homes and other necessary structures. Mud, clay, or a mixture of clay and sand may be used for ceramics, of which one form is the common fired brick. Fired brick consume much more energy to produce. Stabilized mud is mud which has had a binder such as bitumen added. Examples are mudcrete and soil cement. Pottery is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln which removes all the water from the clay, which induces reactions that lead to permanent changes including increasing their strength and hardening and setting their shape.
A clay body can be decorated after firing. Prior to some shaping processes, clay must be prepared. Kneading helps to ensure an moisture content throughout the body. Air trapped within the clay body needs to be removed; this is called de-airing and can be accomplished by a machine called a vacuum pug or manually by wedging. Wedging can help produce an moisture content. Once a clay body has been kneaded and de-aired or wedged, it is shaped by a variety of techniques. After shaping it is dried and fired. In ceramics, the making of liquid mud is a stage in the process of refinement of the materials, since larger particles will settle from the liquid. Mud can provide a home for numerous types of animals, including varieties of worms, snails and crayfish. Other animals, such as hippopotamuses, rhinoceroses, water buffalo and elephants, bathe in mud in order to cool off and protect themselves from the sun. Submerged mud can be home to larvae of various insects. Mud plays an important role in the marine ecosystem.
The activities of burrowing animals and fish have a dramatic churning effect on muddy seabeds. This allows the exchange and cycling of oxygen and minerals between water and sediment. Below the surface, the burrows of some species form intricate lattice-like networks and may penetrate a meter or more downwards; this means that the burrowed mud is a productive habitat, providing food and shelter for a wide range of mud-dwellers and other animals that forage in and over the mud. Mud can pose problems for motor traffic when moisture is present, because every vehicle function that changes direction or speed relies on friction between the tires and the road surface, so a layer of mud on the surface of the road or tires can cause the vehicle to hydroplane. Heavy rainfall, snowmelt, or high levels of ground water may trigger a movement of soil or sediments causing mudslides, avalanches, or sinkholes. Mudslides in volcanic terrain occur. Mudslides are common in the western United States during El Niño years due to prolonged rainfall.
There are numerous dysphemisms for poor-tasting food such as "tastes like dirt". Kava tea is described this way, as it is bitter and contains sediments. There exist children's recipes for "mud", a chocolate or cornstarch-based sludge used more for visual appeal than actual taste. Never does this confectionery mud contain real mud; the practice of eating earth or soil-like substances is geophagia. A mud bath is a bath of mud from areas where hot spring water can combine with volcanic ash. Mud baths have existed for thousands of years, can be found now in high-end spas in many countries of the world. Mud wallows are a common source of entertainment for kids. Mud wallows can be any shape, size and some can have water as well as mud. Wallows are shallow dips in the ground that have been flooded and were full of dirt and those two have mixed to make a squishy mud wallow. Mud bogging is a form of off-road motorsport popular in Canada and the United States in which the goal is to drive a vehicle through a pit of m
Silt is granular material of a size between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil or as sediment mixed in suspension with water and soil in a body of water such as a river, it may exist as soil deposited at the bottom of a water body, like mudflows from landslides. Silt has a moderate specific area with a non-sticky, plastic feel. Silt has a floury feel when dry, a slippery feel when wet. Silt can be visually observed with a hand lens, it can be felt by the tongue as granular when placed on the front teeth. Silt is created by a variety of physical processes capable of splitting the sand-sized quartz crystals of primary rocks by exploiting deficiencies in their lattice; these involve chemical weathering of rock and regolith, a number of physical weathering processes such as frost shattering and haloclasty. The main process is abrasion through transport, including fluvial comminution, aeolian attrition and glacial grinding, it is in semi-arid environments.
Silt is sometimes known as "rock flour" or "stone dust" when produced by glacial action. Mineralogically, silt is composed of quartz and feldspar. Sedimentary rock composed of silt is known as siltstone. Liquefaction created by a strong earthquake is silt suspended in water, hydrodynamically forced up from below ground level. In the Udden–Wentworth scale, silt particles range between 0.0039 and 0.0625 mm, larger than clay but smaller than sand particles. ISO 14688 grades silts between 0.063 mm. In actuality, silt is chemically distinct from clay, unlike clay, grains of silt are the same size in all dimensions. Clays are formed from thin plate-shaped particles held together by electrostatic forces, so present a cohesion. Pure silts are not cohesive. According to the U. S. Department of Agriculture Soil Texture Classification system, the sand–silt distinction is made at the 0.05 mm particle size. The USDA system has been adopted by the Agriculture Organization. In the Unified Soil Classification System and the AASHTO Soil Classification system, the sand–silt distinction is made at the 0.075 mm particle size.
Silts and clays are distinguished mechanically by their plasticity. Silt is transported in water or other liquid and is fine enough to be carried long distances by air in the form of dust. Thick deposits of silty material resulting from deposition by aeolian processes are called loess. Silt and clay contribute to turbidity in water. Silt is transported by water currents in the ocean; when silt appears as a pollutant in water the phenomenon is known as siltation. Silt, deposited by annual floods along the Nile River, created the rich, fertile soil that sustained the Ancient Egyptian civilization. Silt deposited by the Mississippi River throughout the 20th century has decreased due to a system of levees, contributing to the disappearance of protective wetlands and barrier islands in the delta region surrounding New Orleans. In southeast Bangladesh, in the Noakhali district, cross dams were built in the 1960s whereby silt started forming new land called "chars"; the district of Noakhali has gained more than 73 square kilometres of land in the past 50 years.
With Dutch funding, the Bangladeshi government began to help develop older chars in the late 1970s, the effort has since become a multi-agency operation building roads, embankments, cyclone shelters and ponds, as well as distributing land to settlers. By fall 2010, the program will have allotted some 100 square kilometres to 21,000 families. A main source of silt in urban rivers is disturbance of soil by construction activity. A main source in rural rivers is erosion from plowing of farm fields, clearcutting or slash and burn treatment of forests; the fertile black silt of the Nile river's banks is a symbol of rebirth, associated with the Egyptian god Anubis. Erosion control Nonpoint source pollution Sediment control Silt fence Siltation