A spit or sandspit is a deposition bar or beach landform found off coasts or lake shores. It develops in places where re-entrance occurs, such as at a coves headlands, the drift occurs due to waves meeting the beach at an oblique angle, moving sediment down the beach in a zigzag pattern. This is complemented by longshore currents, which further transport sediment through the water alongside the beach and these currents are caused by the same waves that cause the drift. Where the direction of the shore inland re-enters, or changes direction, for example at a headland, no longer able to carry the full load, much of the sediment is dropped. This submerged bar of sediment allows longshore drift or littoral drift to continue to transport sediment in the direction the waves are breaking, forming an above-water spit. Without the complementary process of littoral drift, the bar would not build above the surface of the becoming an spit. Spits occur when longshore drift reaches a section of headland where the turn is greater than 30 degrees, the spit will continue out into the sea until water pressure becomes too great to allow the sand to deposit.
Vegetation may start to grow on the spit, and the spit may become stable, a spit may be considered a special form of a shoal. As spits grow, the water behind them is sheltered from wind and waves, wave refraction can occur at the end of a spit, carrying sediment around the end to form a hook or recurved spit. Refraction in multiple directions may create a complex spit, waves that arrive in a direction other than obliquely along the spit will halt the growth of the spit, shorten it, or eventually destroy it entirely. The sediments that make up spits come from a variety of sources including rivers and eroding bluffs, activities such as logging and farming upstream can increase the sediment load of rivers, which may hurt the intertidal environments around spits by smothering delicate habitats. Roads or bulkheads built along bluffs can drastically reduce the volume of sediment eroded, if the supply of sediment is interrupted the sand at the neck of the spit may be moved towards the head, eventually creating an island.
If the supply is not interrupted, and the spit is not breached by the sea, if an island lies offshore near where the coast changes direction, and the spit continues to grow until it connects the island to the mainland, it is called a tombolo. The end of an attached to land is called the proximal end. The longest spit in the world is the Arabat Spit in the Sea of Azov and it is approximately 110 kilometres long. The longest spit in a body of water is Long Point, Ontario. A well-known spit in the UK is Spurn Point at the mouth of the Humber River, the Curonian Spit, off the coast of Lithuania and Kaliningrad Oblast of Russia, separates the Curonian Lagoon from the Baltic Sea, it is 98 km long. In a similar fashion, the Vistula Spit separates the Vistula Lagoon from the Gdańsk Bay off the coast of Poland, the spit bends slightly west or east, changing its direction gradually, depending on the conditions of the tides and weather
A sea is a large body of salt water that is surrounded in whole or in part by land. More broadly, the sea is the system of Earths salty. The sea moderates Earths climate and has important roles in the cycle, carbon cycle. Although the sea has been traveled and explored since prehistory, the scientific study of the sea—oceanography—dates broadly to the British Challenger expedition of the 1870s. Owing to the present state of continental drift, the Northern Hemisphere is now equally divided between land and sea but the South is overwhelmingly oceanic. Salinity in the ocean is generally in a narrow band around 3. 5% by mass, although this can vary in more landlocked waters, near the mouths of large rivers. About 85% of the solids in the sea are sodium chloride. Deep-sea currents are produced by differences in salinity and temperature, surface currents are formed by the friction of waves produced by the wind and by tides, the changes in local sea level produced by the gravity of the Moon and Sun.
The direction of all of these is governed by surface and submarine land masses, former changes in sea levels have left continental shelves, shallow areas in the sea close to land. The most diverse areas surround great tropical coral reefs, whaling in the deep sea was once common but whales dwindling numbers prompted international conservation efforts and finally a moratorium on most commercial hunting. Life may have started there and aquatic microbial mats are generally credited with the oxygenation of Earths atmosphere, the sea is an essential aspect of human trade, mineral extraction, and power generation. It is the scene of activities including swimming, surfing. However, population growth, industrialization, and intensive farming have all contributed to marine pollution. Atmospheric carbon dioxide is being absorbed in increasing amounts, lowering its pH in a known as ocean acidification. The shared nature of the sea has made overfishing an increasing problem, both senses of sea date to Old English, the larger sense has required a definite article since Early Middle English.
Seas are generally larger than lakes and contain salt water, while the defining elements of size and being bounded are generally used, there is no formally accepted technical definition of sea among oceanographers. In international law, the United Nations Convention on the Law of the Sea states that all the ocean is the sea. Earth is the known planet with seas of liquid water on its surface, although Mars possesses ice caps
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume.
In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume.
As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This occurs where a river enters an ocean, estuary, reservoir, River deltas are ecologically important as they provide coastline defense, are home to many species, and can impact drinking water supply. The tidal currents cannot be too strong, as sediment would wash out into the body faster than the river deposits it. Of course, the river must carry enough sediment to layer into deltas over time, the rivers velocity decreases rapidly, causing it to deposit the majority, if not all, of its load. This alluvium builds up to form the river delta, when the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, as a result, sediment drops out of the flow and deposits. Over time, this single channel builds a deltaic lobe, pushing its mouth into the standing water, as the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation.
As the slope of the channel decreases, it becomes unstable for two reasons. First, gravity makes the flow in the most direct course down slope. If the river breaches its natural levees, it out onto a new course with a shorter route to the ocean. Second, as its slope gets lower, the amount of stress on the bed decreases, which results in deposition of sediment within the channel. This makes it easier for the river to breach its levees, often when the channel does this, some of its flow remains in the abandoned channel. When these channel-switching events occur, a mature delta develops a distributary network, another way these distributary networks form is from deposition of mouth bars. When this mid-channel bar is deposited at the mouth of a river and this results in additional deposition on the upstream end of the mouth-bar, which splits the river into two distributary channels. A good example of the result of this process is the Wax Lake Delta, in both of these cases, depositional processes force redistribution of deposition from areas of high deposition to areas of low deposition.
This results in the smoothing of the shape of the delta as the channels move across its surface. Because the sediment is laid down in fashion, the shape of these deltas approximates a fan. The more often the flow changes course, the shape develops as closer to an ideal fan, the Mississippi and Ural River deltas, with their birds-feet, are examples of rivers that do not avulse often enough to form a symmetrical fan shape
A river is a natural flowing watercourse, usually 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 term river as applied to geographic features. Many names for small rivers are specific to geographic location, examples are run in parts of the United States, burn in Scotland and northeast England. Sometimes a river is defined as being larger than a creek, but not always, Rivers are part of the hydrological cycle. Potamology is the study of rivers while limnology is the study of inland waters in general. Extraterrestrial rivers of liquid hydrocarbons have recently found on Titan. Channels may indicate past rivers on other planets, specifically outflow channels on Mars and rivers are theorised to exist on planets, a river begins at a source, follows a path called a course, and ends at a mouth or mouths.
The water in a river is confined to a channel. In larger rivers there is 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, especially in areas where the floodplain of a river channel can become greatly developed by housing. Rivers can flow down mountains, through valleys or along plains, the term upriver refers to the direction towards the source of the river, i. e. against the direction of flow. Likewise, the term describes the direction towards the mouth of the river. The term left bank refers to the bank in the direction of flow. The river channel typically contains a stream of water, but some rivers flow as several interconnecting streams of water. Extensive braided rivers are now found in only a few regions worldwide and they occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are quite rare
For sediment in beverages, see dregs. For example and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but wind, 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 transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, 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 both a size-range and 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 and streams carry sediment in their flows.
This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is 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, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and 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, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and 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 can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
The River Sid is a minor river in East Devon. It flows for 10.5 kilometres southwards from a source in Crowpits Covert at a height of 206 metres above sea level, the source is at the head of a goyle or small ravine. The underlying geology is impermeable silty mudstones and sandstones of the Triassic Keuper marl, overlain with permeable Greensand, the junction between the Greensand and Keuper Marl forms a spring line. The river flows through Sidbury and Sidford to Sidmouth and is fed by springs flowing from East Hill and water from the Roncombe Stream, the Snod Brook, in Sidmouth the river outflows at the Ham through a shingle bar. The Sid Vale Association, the first Civic Society in Britain is based in the Sid Vale
The River Yare is a river in the English county of Norfolk. In its lower reaches it is one of the navigable waterways of The Broads. The river rises south of Dereham to the west to the village of Shipdham, above its confluence with a tributary stream from Garvestone it is known as the Blackwater River. From there it flows in an eastward direction passing Barnham Broom and is joined by the River Tiffey before reaching Bawburgh. It skirts the southern fringes of the city of Norwich, passing through Colney, Cringleford and Trowse. At Whitlingham it is joined by the River Wensum and although the Wensum is the larger and longer of the two, the downstream of their confluence continues to be called the Yare. Flowing eastward into The Broads it passes the villages of Bramerton, Rockland St. Mary, just before Reedham at Hardley Cross it is joined by the River Chet. The cross marks the ancient boundary between the City of Norwich and Borough of Great Yarmouth, beyond Reedham the river passes the famously isolated marshland settlement of Berney Arms before entering the tidal lake of Breydon Water.
Here the Yare is joined by the Rivers Waveney and Bure and finally enters the North Sea at Gorleston, the Yare is the frequent subject of landscape paintings by members of the early 19th century Norwich School of artists. The National Gallery of Art in Washington D. C. contains an oil painting by John Crome entitled Moonlight on the Yare, joseph Stannard depicted the river in Thorpe Water Frolic and Boats on the Yare near Bramerton which is in the Fitzwilliam Museum, Cambridge. The river is navigable to small vessels from Norwich to the sea. At Reedham the river is joined by the Haddiscoe Cut, a canal which provides a navigable link to the River Waveney at Haddiscoe avoiding Breydon Water. The river provides a link between Norwich and the North Sea, but silting has been a long-standing problem. In 1698, an Act of Parliament was obtained which allowed duty to be collected for any traffic using the river. Three more acts attempted to rectify the situation, but the continued to be neglected. A fifth act, obtained in 1772, sought to address the problem in a different way, other rivers benefitted from the remaining 20 per cent.
In order to improve the situation the merchants of Norwich asked William Cubitt to look for a solution in 1814 and his proposal consisted of dredging a new channel to the south side of Breydon Water and making various improvements to the river. This was costed at £35,000, but the plan was opposed by Yarmouth Corporation when it was public in 1818
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. Some shorelines experience a semi-diurnal tide—two nearly equal high and low tides each day, other locations experience a diurnal tide—only one high and low tide each day. A mixed tide—two uneven tides a day, or one high, Tides vary on timescales ranging from hours to years due to a number of factors. To make accurate records, tide gauges at fixed stations measure water level over time, gauges ignore variations caused by waves with periods shorter than minutes. These data are compared to the level usually called mean sea level. Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field varies in time. For example, the part of the Earth is affected by tides. Tide changes proceed via the following stages, Sea level rises over several hours, covering the intertidal zone, the water rises to its highest level, reaching high tide.
Sea level falls over several hours, revealing the intertidal zone, the water stops falling, reaching low tide. Oscillating currents produced by tides are known as tidal streams, the moment that the tidal current ceases is called slack water or slack tide. The tide reverses direction and is said to be turning, slack water usually occurs near high water and low water. But there are locations where the moments of slack tide differ significantly from those of high, Tides are commonly semi-diurnal, or diurnal. The two high waters on a day are typically not the same height, these are the higher high water. Similarly, the two low waters each day are the low water and the lower low water. The daily inequality is not consistent and is small when the Moon is over the equator. From the highest level to the lowest, Highest Astronomical Tide – The highest tide which can be predicted to occur, note that meteorological conditions may add extra height to the HAT. Mean High Water Springs – The average of the two high tides on the days of spring tides, mean High Water Neaps – The average of the two high tides on the days of neap tides.
Mean Sea Level – This is the sea level
Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration. This is referred to as the movement of a substance down a concentration gradient, a gradient is the change in the value of a quantity with the change in another variable. The word diffusion derives from the Latin word, which means to spread out, a distinguishing feature of diffusion is that it results in mixing or mass transport, without requiring bulk motion. Thus, diffusion should not be confused with convection, or advection, an example of a situation in which bulk flow and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration. The lungs are located in the cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs and this creates a pressure gradient between the air outside the body and the alveoli. The air moves down the gradient through the airways of the lungs and into the alveoli until the pressure of the air.
The air arriving in the alveoli has a concentration of oxygen than the “stale” air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli, oxygen moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases and this creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli. The pumping action of the heart transports the blood around the body, as the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a gradient between the heart and the capillaries, and blood moves through blood vessels by bulk flow. The concept of diffusion is widely used in, chemistry, sociology, however, in each case, the object that is undergoing diffusion is “spreading out” from a point or location at which there is a higher concentration of that object.
In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion, according to Ficks laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration, some time later, various generalizations of Ficks laws were developed in the frame of thermodynamics and non-equilibrium thermodynamics. From the atomistic point of view, diffusion is considered as a result of the walk of the diffusing particles. In molecular diffusion, the molecules are self-propelled by thermal energy. Random walk of small particles in suspension in a fluid was discovered in 1827 by Robert Brown, the theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein
Often it refers to those submerged ridges, banks, or bars that rise near enough to the surface of a body of water as to constitute a danger to navigation. Shoals are known as sandbanks, sandbars, or gravelbars, two or more shoals that are either separated by shared troughs or interconnected by past and or present sedimentary and hydrographic processes are referred to as a shoal complex. The term shoal is used in a number of ways that can be similar or quite different from how it is used in the geologic, geomorphic. Shoals are characteristically long and narrow ridges and they can develop where a stream, river, or ocean current promotes deposition of sediment and granular material, resulting in localized shallowing of the water. Marine shoals develop either by the in place drowning of barrier islands as the result of sea level rise or by the erosion. Shoals can appear as a coastal landform in the sea, where they are classified as a type of bank, or as fluvial landforms in rivers, streams. A shoal–sandbar may seasonally separate a smaller body of water from the sea, such as, Marine lagoons Brackish water estuaries Freshwater seasonal stream and river mouths and deltas.
They are typically composed of sand, although they could be of any matter that the moving water has access to and is capable of shifting around. Wave shoaling is the process when surface waves move towards shallow water, such as a beach, they slow down, their wave height increases and this behavior is called shoaling, and the waves are said to shoal. The waves may or may not build to the point where they break, depending on how large they were to begin with, in particular, waves shoal as they pass over submerged sandbanks or reefs. This can be treacherous for boats and ships, shoaling can diffract waves, so the waves change direction. For example, if waves pass over a bank which is shallower at one end than the other. Thus the wave fronts will refract, changing direction like light passing through a prism, refraction occurs as waves move towards a beach if the waves come in at an angle to the beach, or if the beach slopes more gradually at one end than the other. Sandbars, known as a trough bars, form where the waves are breaking, sometimes this occurs seaward of a trough.
Sand carried by the moving bottom current is deposited where the current reaches the wave break. Other longshore bars may lie further offshore, representing the point of even larger waves. A harbor or river bar is a sedimentary deposit formed at an entrance or river mouth by. Where beaches are suitably mobile, or the river’s suspended and/or bed loads are large enough, deposition can build up a sandbar that completely blocks a river mouth and damming the river
A lake is an area of variable size filled with water, localized in a basin, that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams, natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers, in some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will fill in with sediments or spill out of the basin containing them. The word lake comes from Middle English lake, from Old English lacu, from Proto-Germanic *lakō, cognates include Dutch laak, Middle Low German lāke as in, de, Moorlake, de, Wolfslake, de, German Lache, and Icelandic lækur.
Also related are the English words leak and leach, none of these definitions completely excludes ponds and all are difficult to measure. For this reason, simple size-based definitions are used to separate ponds. One definition of lake is a body of water of 2 hectares or more in area, others have defined lakes as waterbodies of 5 hectares and above, or 8 hectares and above. Charles Elton, one of the founders of ecology, regarded lakes as waterbodies of 40 hectares or more. The term lake is used to describe a feature such as Lake Eyre. In common usage, many bear names ending with the word pond. One textbook illustrates this point with the following, In Newfoundland, for example, almost every lake is called a pond, whereas in Wisconsin, the majority of lakes on Earth are fresh water, and most lie in the Northern Hemisphere at higher latitudes. Canada, with a drainage system has an estimated 31,752 lakes larger than 3 square kilometres and an unknown total number of lakes. Finland has 187,888 lakes 500 square metres or larger, most lakes have at least one natural outflow in the form of a river or stream, which maintain a lakes average level by allowing the drainage of excess water.
Some lakes do not have an outflow and lose water solely by evaporation or underground seepage or both. Many lakes are artificial and are constructed for power generation, aesthetic purposes, recreational purposes, industrial use. Globally, lakes are greatly outnumbered by ponds, of an estimated 304 million standing water bodies worldwide, 91% are 1 hectare or less in area