Clay is a naturally occurring material composed primarily of finegrained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried andor fired. Clay deposits are mostly composed of clay minerals phyllosilicate minerals, minerals which impart plasticity and harden when fired andor dried, and variable amounts of water trapped in the mineral structure by polar attraction. Organic materials which do not impart plasticity may also be a part of clay deposits.Clay minerals are typically formed over long periods of time by the gradual chemical weathering of rocks usually silicatebearing by low concentrations of carbonic acid and other diluted solvents. These solvents usually acidic migrate through the weathering rock after leaching through upper weathered layers. In addition to the weathering process, some clay minerals are formed by hydrothermal activity. Clay deposits may be formed in place as residual deposits, but thick deposits usually are formed as the result of a secondary sedimentary deposition process after they have been eroded and transported from their original location of formation. Clay deposits are typically associated with very low energy depositional environments such as large lake and marine deposits.DefinitionClays are distinguished from other finegrained soils by various differences in composition. Silts, which are finegrained soils which do not include clay minerals, tend to have larger particle sizes than clays, but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include both silts and clays. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of µm clays being finer than silts, sedimentologists often use µm, and colloid chemists use µm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg Limits. ISO grades clay particles as being smaller than . mm, and silts larger.Quaternary clay in Estonia.Quaternary clay in Estonia.Primary clays, also known as kaolins are located at the site of formation. Secondary clay deposits have been moved by erosion and water from its primary location.edit GroupingDepending upon academic source, there are three or four main groups of clays kaolinite, montmorillonitesmectite, illite, and chlorite. Chlorites are not always considered a clay, sometimes being classified as a separate group within the phyllosilicates. There are approximately thirty different types of pure clays in these categories, but most natural clays are mixtures of these different types, along with other weathered minerals.Varve or varved clay is clay with visible annual layers, formed by seasonal differences in erosion and organic content. This type of deposit is common in former glacial lakes.
Quick clay is a unique type of marine clay indigenous to the glaciated terrains of Norway, Canada and Sweden. It is a highly sensitive clay, prone to liquefaction, which has been involved in several deadly landslides.edit Historical and modern usesClay layers in a construction site. Dry clay is normally much more stable than sand with regards to excavations.Clay layers in a construction site. Dry clay is normally much more stable than sand with regards to excavations.Clays exhibit plasticity when mixed with water in certain proportions. When dry, clay becomes firm and when fired in a kiln, permanent physical and chemical reactions occur which, amongst other changes, causes the clay to be converted into a ceramic material. It is because of these properties that clay is used for making pottery items, both practical and decorative. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware and porcelain. Early humans discovered the useful properties of clay in prehistoric times, and one of the earliest artifacts ever uncovered is a drinking vessel made of sundried clay.citation needed Depending on the content of the soil, clay can appear in various colors, from a dull gray to a deep orangered.Clay tablets were used as the first writing medium, inscribed with cuneiform script through the use of a blunt reed called a stylus.Clays sintered in fire were the first form of ceramic. Bricks, cooking pots, art objects, dishware and even musical instruments such as the ocarina can all be shaped from clay before being fired. Clay is also used in many industrial processes, such as paper making, cement production and chemical filtering. Clay is also often used in the manufacture of pipes for smoking tobacco.Clay, being relatively impermeable to water, is also used where natural seals are needed, such as in the cores of dams, or as a barrier in landfills against toxic seepage lining the landfill, preferably in combination with geotextiles.Recent studies have been carried out to investigate clays adsorption capacities in various applications, such as the removal of heavy metals from waste water and air purification.
A recent article in The Journal of Antimicrobial Chemotherapy found that certain ironrich clay was effective in killing bacteria.Clay animationFrom Wikipedia, the free encyclopediaJump to navigation, searchClay animation is one of many forms of stop motion animation. Each animated piece, either character or background, is deformable—made of a malleable substance, usually Plasticine clay. The portmanteau term Claymation is a registered trademark in the United States, registered by Will Vinton in to describe his clay animated films. While the word is not considered a genericized trademark, it has become a trademark which is often used generically in the US to refer to any animation using plasticene or similar substance.All traditional animation is produced in a similar fashion, whether done through cel animation or stopmotion. Each frame, or still picture, is recorded on film or digital media and then played back in rapid succession. When played back at a frame rate greater than frames per second, a fairly convincing illusion of continuous motion is achieved. While the playback feature creating an illusion is true of all moving image from zoetrope, to films to videogames, the techniques involved in creating CGI are generally removed from a framebyframe process.TechniqueIn clay animation, which is one of the many forms of stop motion animation, each object is sculpted in clay or a similarly pliable material such as Plasticine, usually around a wire skeleton called an armature. As in other forms of object animation, the object is arranged on the set background, a film frame is taken and the object or character is then moved slightly by hand. Another frame is taken and the object moved slightly again. This cycle is repeated until the animator has achieved the desired amount of film. The human mind processes the series of slightly changing, rapidly playing images as motion, hence making it appear that the object is moving by itself. To achieve the best results, a consistent shooting environment is needed to maintain the illusion of continuity. This means paying special attention to maintaining consistent lighting and object placement and working in a calm environment.edit ProductionProducing a stop motion animation using clay is extremely laborious. Normal film runs at frames per second frames. With the standard practice of doubles or twos doubleframing — exposing frames for each shot, changes are usually made for one second of film movement. For a minute movie, there would be approximately , stops to change the figures for the frames. For a full length min movie, there would be approximately , stops and possibly far more if parts were shot with singles or ones one frame exposed for each shot. Great care must be taken to ensure the object is not altered by accident, by even slight smudges, dirt, hair, or even dust. For featurelength productions, the use of clay has generally been supplanted by rubber silicone and resincast components. One foamrubber process has been coined as Foamation by Will Vinton. However, clay remains a viable animation material where a particular aesthetic is desired.A subvariation of clay animation can be informally called clay melting.citation needed Any kind of heat source can be applied on or near or below clay to cause it to melt while an animation camera on a timelapse setting slowly films the process. An example of this can be seen in Vintons early short clayanimated film, Closed Mondays, coproduced by animator Bob Gardiner at the end of the computer sequence. A similar technique was used in the climax scene of Raiders of the Lost Ark to melt the faces of the antagonists.
TypesClay animation can take several formsFreeform clay animation is an informal term where the shape of the clay changes radically as the animation progresses, such as in the work of Eliot Noyes Jr and Ivan Stangs animated films. Or clay can take the form of character clay animation where the clay maintains a recognizable character throughout a shot, as in Art Clokeys and Will Vintons films.One variation of clay animation is stratacut animation in which a long breadlike loaf of clay, internally packed tight and loaded with varying imagery, is sliced into thin sheets, with the camera taking a frame of the end of the loaf for each cut, eventually revealing the movement of the internal images within. Pioneered in both clay and blocks of wax by German animator Oskar Fischinger during the s and s, the technique was revivied and highly refined in the mids by David Daniels, an associate of Will Vinton, in his minute short film Buzz Box.Another clay animation technique, and blurring the distinction between stop motion and traditional flat animation, is called clay painting which is also a variation of the direct manipulation animation process where clay is placed on a flat surface and moved like wet oil paints as on a traditional artistic canvas to produce any style of images, but with a clay look to them.edit Video Exampleedit HistoryPlease help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. May Pioneering this technique was onetime Vinton animator Joan Gratz, first in her Oscarnominated film The Creation and then in her Oscarwinning Mona Lisa Descending a Staircase filmed in .Already animated André Roche in the Cineplast Films Studio of Marc Chinoy in Munich Germany several films for a serie named KliKlaKlawitter for the Second German TVChannel ZDF, for a german language teatching serie for foreign children and another one for a traffic education serie Herr Daniel paßt auf = Mr. Daniel cares of.A variation of this technique was developed by another Vinton animator, Craig Bartlett, for his series of Arnold short films, also made during the s, in which he not only used clay painting, but sometimes built up clay images that rose off the plane of the flat suppot platform, toward the camera lens, to give a more D stopmotion look to his films.Some of the bestknown clayanimated works include the Gumby series of television show segments created by Art Clokey, and the TV commercial made for the California Raisin Advisory Board by Vintons studio. Clay animation has also been used in AcademyAwardwinning short films such as Closed Mondays Will Vinton and Bob Gardiner, , Creature Comforts Aardman, , and all three Wallace & Gromit short films, created by Nick Park of Aardman Animation. Aardman also created The Presentators, a series of oneminute clayanimation short films aired on Nicktoons. Some clay animations appear online, on such sites as Newgrounds.Several computer games have also been produced using clay animation, including The Neverhood, Dark Oberon, Clay Fighter, Platypus and Primal Rage. Television commercials have also utilized the clay animation, such as the Chevron Cars ads, produced by Aardman Studios. Besides commercials, clay animation has also been popularized in recent years by childrens shows such as Bob the Builder and The Koala Brothers, as well as adultoriented shows on Cartoon Networks Adult Swim lineup, including Robot Chicken which uses clay animation and action figures as stopmotion puppets in conjunction and Moral Orel. Many independent young film makers have used clay animation features for internet viewing.
Flushed Away is a CGI replication
Flushed Away is a CGI replication of clay animation.A clay court is one of the four different types of tennis court. Clay courts are made of crushed shale, stone or brick. The red clay is slower than the green, or HarTru American clay. The French Open uses clay courts, making it unique among the Grand Slam tournaments.Although more traditional and cheaper to construct than other types of tennis courts, maintenance costs of clay courts are higher than those of hard courts. Clay courts need to be rolled to preserve flatness. The clays water content must be balanced green courts generally require the courts to be sloped to allow water runoff.Clay courts are more common in Europe and South America than in North America. In the United States, courts made of green clay, also known as rubico, are often called clay, but are not made of the same clay used in most European and South American countries.PlayClay courts favour the full western grip for more topspin. Clay courters generally play in a semi circle about to feet behind the baseline.Clay courts are considered slow, because the balls bounce relatively high and more slowly, making it more difficult for a player to hit an unreturnable shot. Points are usually longer as there are fewer winners. Therefore, clay courts heavily favour baseliners who are consistent and are generally more defensive.Clay court players use drop shots to throw off their opponents. Movement on Gravel courts is very different to movement on any other surface. Playing on clay often involves the ability to slide into the ball during the stroke, as opposed to running and stopping like on a hard or grass court. This often causes problems for players who are not used to this type of movement.Players who excel on clay courts but struggle to replicate the same form on fast courts are known as claycourt specialists.edit Types of clayThere are two different types of clayedit Red clayRed clay is made of crushed brick that is packed to make the court. It is then covered with a topping of additional crushed particles. Some natural clay courts exist, but the courts that utilise crushed brick do not absorb water easily, whereas natural clay courts take two to three days to dry. This surface is the most common in Europe and South America.edit Green clayGreen clay, HarTru or American clay, is similar to red clay, the differences being that it is slightly harder and faster. Green clay is packed to make the subsurface. It is then covered with a topping. These clay courts are found primarily in the Eastern and Southern parts of the United States, but are also located in all states. In parts of the gulf coast region of the Southeast, green clay courts are often referred to as rubico. There are two major ATPWTA tournaments played on green HarTru clay courts the Family Circle Cup in Charleston, SC, and The Bausch and Lomb Championships in Amelia Island, FL.
PlayersThe most successful female player recently was Justine Henin, a fourtime French Open singles champion. Her variety in the shots, speed, footwork and her slices were her biggest weapons. The most successful current male player is Rafael Nadal, winner of the last four French Open mens singles titles in fact he has never lost a match at that tournament and current holder of the longest winning streak by any male player on a single surface clay court wins between April and May .Chris Evert holds the record for longest winning streak on clay for either gender from August to May , , she won consecutive clay court matches.Clay mineralsFrom Wikipedia, the free encyclopediaJump to navigation, searchOxford Clay Jurassic exposed near Weymouth, England.Oxford Clay Jurassic exposed near Weymouth, England.Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths and other cations. Clays have structures similar to the micas and therefore form flat hexagonal sheets. Clay minerals are common weathering products including weathering of feldspar and low temperature hydrothermal alteration products. Clay minerals are very common in fine grained sedimentary rocks such as shale, mudstone and siltstone and in fine grained metamorphic slate and phyllite.Clay minerals include the following groups Kaolin group which includes the minerals kaolinite, dickite, halloysite and nacrite. Some sources include the serpentine group due to structural similarities Bailey . Smectite group which includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite. Illite group which includes the claymicas. Illite is the only common mineral.Chlorite group includes a wide variety of similar minerals with considerable chemical variation. istoryKnowledge of the nature of clay became better understood in the s with advancements in microscope technology necessary to analyze the infinitesimal nature of clay particles. Standardization in terminology arose during this period as well with special attention given to similar words that resulted in confusion such as sheet and plane.edit StructureLike all phyllosilicates, clay minerals are characterised by twodimensional sheets of corner sharing SiO and AlO tetrahedra. These tetrahedral sheets have the chemical composition Al,SiO, and each tetrahedron shares of its vertex oxygen atoms with other tetrahedra forming a hexagonal array in twodimensions. The fourth vertex is not shared with another tetrahedron and all of the tetrahedra point in the same direction i.e. all of the unshared vertices are on the same side of the sheet.In clays the tetrahedral sheets are always bonded to octahedral sheets formed from small cations, such as aluminium or magnesium, coordinated by six oxygen atoms. The unshared vertex from the tetrahedral sheet also form part of one side of the octahedral sheet but an additional oxygen atom is located above the gap in the tetrahedral sheet at the center of the six tetrahedra. This oxygen atom is bonded to a hydrogen atom forming an OH group in the clay structure. Clays can be categorised depending on the way that tetrahedral and octahedral sheets are packaged into layers. If there is only one tetrahedral and one octahedral group in each layer the clay is known as a clay. The alternative, known as a clay, has two tetrahedral sheets with the unshared vertex of each sheet pointing towards each other and forming each side of the octahedral sheet.
Bonding between the tetrahedral
Bonding between the tetrahedral and octahedral sheets requires that the tetrahedral sheet becomes corrogated or twisted, causing ditrigonal distortion to the hexagonal array, and the octahedral sheet is flattened. This minimizes the overall bondvalence distortions of the crystallite.Depending on the composition of the tetrahedral and octahedral sheets, the layer will have no charge, or will have a net negative charge. If the layers are charged this charge is balanced by interlayer cations such as Na+ or K+. In each case the interlayer can also contain water. The crystal structure is formed from a stack of layers interspaced with the interlayers.Clay pitFrom Wikipedia, the free encyclopediaJump to navigation, searchA clay pit is a quarry or mine for the extraction of clay, which is generally used for manufacturing pottery or bricks.The brick factory is often located alongside the clay pit to reduce the transport costs of the raw material. These days pottery producers are often not sited near the source of their clay and usually do not own the clay deposits. The other essential raw material is fuel for firing and potteries may be located near to fuel deposits rather than the clay.Former claypits are sometimes filled with water and used for recreational purposes such as sailing and scuba diving. The Eden Project, near St Austell, Cornwall, UK is a major development of a former china clay pit for educational and environmental purposes.Nylonreinforced clayA relatively new product variation of earthen clay is clay reinforced with filaments of Nylon. It is used by modellers who do not intend to fire their works. This is designed to bond the clay more tightly and therefore reduce the incidence of cracking.Modelling large models with earthen clays is made difficult because clay shrinks unevenly when it dries. It is therefore essential that the model is dried very slowly otherwise fatal cracking occurs.Cracking can also be minimised by using an internal supporting frame armature of wood, wire mesh, polystyrene or similar materials made to the rough shape of the intended object and then finishing the model with a layer of clay no more than mm thick.edit Firing earthen modelling clayModeling clays both natural and Nylon reinforced can be fired at a kiln temperature in the range of °C to °C. When firing a model, modellers should take care to ensure that their armature frame can withstand these temperatures without breaking down or releasing explosive or noxious fumes. Models can then be glazed in the same way as pottery clay. The Nylon does not affect the glazing process.edit Plasticinelasticine was invented in by William Harbutt of Bathampton, near Bath, Somerset, England, an art teacher who wanted a nondrying clay for use by his sculpture students. Since then, Plasticine has since become a generic term, especially in the Commonwealth, for modelling clay.As well as being very slow drying, Plasticine has other properties of advantage to artists. Being oilbased, it is not soluble in water. When warmed to body temperature of around °C, it is easily worked but when cooled to room temperature of around °C, it stiffens and becomes very stable. It can be reused and so is an ideal material for animation artists who need to rework their models. It is available in a multitude of colours, is nontoxic and is therefore suitable for use by children.
Being readily worked in fine detail, Plasticine is also suitable for the creation of an original work from which a mould molding can be made. Castings and reproductions in a much more durable material can then be produced.There is now a variety of similar products on the market, including in the UK Newplast and Colour Clay.edit Polymer clayPolymer clay is a type of clay that will harden permanently when baked at a low temperature. Polymer clay hardens by curing at temperatures created in a typical home oven generally at to °F to °C for minutes per mm of thickness and does not shrink or change texture during the process. When properly cured, most items wont break if dropped or normally stressed. Polymer clay also comes in liquid form and in permanently flexible solid form. Polymer clay is sold in craft, hobby, and art stores, and is used by artists, hobbyists and children. Leading brands of polymer clay include Premo, FimoClassic and FimoSoft, Kato Polyclay, Sculpey Cernit, Formello and Modello and Das.edit Waxbased clayA modelling clay based on a mix in various proportions of wax, oil and filler materials such as sulfur. Commonly used in clay modeling while developing car designs. Also known as clay industrial plasticine.edit Paper clayThere are two major groups of paper claypaperclay users.There are those using paperclay as an unfired body and those using paperclay in the studio ceramic studio to make sculptural and functional ceramics. Studio ceramics and paperclay Airdrying modeling clayCommercial air drying clay does not shrink noticeably when drying. This paper clay can be painted, varnished, drilled, sawn, cut and glued. There is brand of paper clay called Fun Fair Paper Clay which is aimed at children. Model Magic by Crayola is a similar product.edit See also Papiermâché papermaché, construction material made of paper and a wet pasteThe London Clay is a marine geological formation of Ypresian Lower Eocene Epoch, c. Ma age which crops out in the southeast of England. The London Clay is well known for the fossils it contains. It is the only European source of diverse plant fossils from the Lower Eocene. The fossils indicate a moderately warm climate, the flora being tropical or subtropical. Though sea levels changed during the deposition of the Clay, the habitat was generally a lush forest perhaps like in Indonesia or East Africa today bordering a warm, shallow ocean.
The London Clay consists
The London Clay consists of a stiff, bluish coloured clay which becomes brown when weathered. Nodular lumps of pyrite and crystals of selenite frequently occur within the clay, and large septarian concretions are also common. These have been used in the past for the manufacturing of cement. They were once dug for this purpose at Sheppey, near Sittingbourne, and at Harwich, and also dredged off the Hampshire coast. The clay itself has been used commercially for making bricks, tiles, and coarse pottery. It is infertile for gardens and crops.DistributionThe London Clay is well developed in the London Basin, where it thins westwards from around metres ft in Essex and north Kent to around . metres ft in Wiltshire. though it is not frequently exposed as it is to a great extent covered by more recent neogene sediments and Pleistocene gravel deposits. One location of particular interest is Oxshott Heath, where the overlying sand and the London Clay layers are exposed as a sand escarpment, rising approximately metres. This supported a thriving brick industry in the area until the s. The London Clay is also well developed in the Hampshire Basin, where an exposure metres ft thick occurs at Whitecliff Bay on the Isle of Wight and around metres ft is spread along km of foreshore at Bognor Regis, West Sussex.edit FormationThe clay was deposited in a sea up to metres ft deep at the eastern end. Up to five cycles of deposition representing transgression followed by shallowing of the sea have been found, most markedly at the shallower, western end. Each cycle begins with coarser material sometimes including rounded flint pebbles, followed by clay which becomes increasingly sandy. The final cycle ends with the Claygate Beds.edit Claygate BedsThe youngest part of the London Clay, known as the Claygate Beds or Claygate Member forms a transition between the clay and the sandier Bagshot Beds above. This is shown separately on many geological maps, and often caps hills. It is up to metres ft thick at Claygate, Surrey. It is now believed to be diachronous, with the formation at Claygate for example being the same age as the end of the fourth cycle of deposition further east.
edit Fossil fauna and floraNotable coastal exposures from which fossils can be collected are on the Isle of Sheppey in Kent and WaltonontheNaze, Essex in the London Basin, and Bognor Regis in the Hampshire Basin.Animal fossils include bivalves, gastropods, nautilus, worm tubes, brittle stars and starfish, crabs, lobsters, fish including shark and ray teeth, reptiles particularly turtles, and a large diversity of birds. A few mammal remains have also been recorded. Preservation varies articulated skeletons are generally rare. Of fish, isolated teeth are very frequent. Bird bones are not infrequently encountered compared to other lagerstätten, but usually occur as single bones and are often broken.Plant fossils, including seeds and fruits, may also be found in abundance. The flora demonstrates the much hotter climate of that time, with plants such as Nypa Nipah palms being frequently encountered. Plant fossils have been collected from the London Clay for almost years. Some named species of plant have been found, making the London Clay flora one of the worlds most varied for fossil seeds and fruits.
VertebratesClay industrial plasticineFrom Wikipedia, the free encyclopediaJump to navigation, searchClay or industrial plasticine is a modelling material which is mainly used by automotive design studios. It was developed as an industrial version of plasticine or hobby clay.It is a modelling material based on wax and typically contains sulfur which gives a characteristic smell to most clays. Often, the styled object will be used to create molds from. However, largely because sulfur can interfere with some moldmaking processes, especially if clay surfaces are unsealed surfaces and platinumcure RTV room temperature vulcanizing silicone rubber is used, sulfurfree variants are now available these are usually much lighter than sulfurcontaining clay.edit Design studiosBefore a new car model is launched, a long period of finding the right design takes place. Even today, computer models are not sufficient to evaluate the quality of a design. Therefore or even models are built to get an impression of the final car. These models are created in clay, and usually consist of a wooden or iron frame which is covered with styrofoam. On top of the foam clay is loaded. Modellers then use various tools and slicks to finalise the shape of the car.edit SuppliersMarine clayFrom Wikipedia, the free encyclopediaJump to navigation, searchMarine clay is a type of clay found in coastal regions around the world. In the northern, deglaciated regions, it can sometimes be quick clay, which is notorious for being involved in landslides.Clay particles can selfassemble into various configurations, each with totally different properties.When clay is deposited in the ocean, the excess ions allow a loose, open structure that is open to water infiltration. Once stranded and dried by ancient, changing ocean levels, it becomes a geotechnical engineering challenge. Where clay overlies peat, a lateral coast movent is denoted and shows a rise in relative sea levelWhen investigating the market, the potential homeowner should always be on the lookout for geologic hazards. Marine clay swelling clay has the potential to destroy the foundation in only a few years. Some simple precautions, however, can reduce the hazard significantlycitation needed.FormationSedimentaryrock formation, Karnataka, IndiaSedimentaryrock formation, Karnataka, IndiaSedimentary rocks are formed because of the overburden pressure as particles of sediment are deposited out of air, ice, wind, gravity, or water flows carrying the particles in suspension. As sediment deposition builds up, the overburden or lithostatic pressure squeezes the sediment into layered solids in a process known as lithification rock formation and the original connate fluids are expelled. The term diagenesis is used to describe all the chemical, physical, and biological changes, including cementation, undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface weathering.Sedimentary rocks are laid down in layers called beds or strata. That new rock layers are above older rock layers is stated in the principle of superposition.There are usually some gaps in the sequence called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.
Sedimentary rocks contain
Sedimentary rocks contain important information about the history of Earth. They contain fossils, the preserved remains of ancient plants and animals. Coal is considered a type of sedimentary rock. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains.The sedimentary rock cover of the continents of the Earths crust is extensive, but the total contribution of sedimentary rocks is estimated to be only % of the total. As such, the sedimentary sequences we see represent only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.edit ClassificationSedimentary rocks are classified into three groups. These groups are clastic, chemical precipitate and biochemical or biogenic.edit Clastic Main article Clastic rockClastic sedimentary rocks are composed of discrete fragments or clasts of materials derived from other rocks. They are composed largely of quartz with other common minerals including feldspar, amphiboles, clay minerals, and sometimes more exotic igneous and metamorphic minerals.Clastic sedimentary rocks, such as breccia or sandstone, were formed from rocks that have been broken down into fragments by weathering, which then have been transported and deposited elsewhere.Clastic sedimentary rocks may be regarded as falling along a scale of grain size, with shale being the finest with particles less than . mm, siltstone being a little bigger with particles between . to . mm, and sandstone being coarser still with grains . to mm, and conglomerates and breccias being more coarse with grains to mm. Breccia has sharper particles, while conglomerate is categorized by its rounded particles. Particles bigger than mm are termed blocks angular or boulders rounded. Lutite, Arenite and Rudite are general terms for sedimentary rock with claysilt, sand or conglomeratebrecciasized particles.The classification of clastic sedimentary rocks is complex because there are many variables involved. Particle size both the average size and range of sizes of the particles, composition of the particles, the cement, and the matrix the name given to the smaller particles present in the spaces between larger grains must all be taken into consideration.Shales, which consist mostly of clay minerals, are generally further classified on the basis of composition and bedding.Coarser clastic sedimentary rocks are classified according to their particle size and composition. Orthoquartzite is a very pure quartz sandstone arkose is a sandstone with quartz and abundant feldspar greywacke is a sandstone with quartz, clay, feldspar, and metamorphic rock fragments present, which was formed from the sediments carried by turbidity currents.All rocks disintegrate when exposed to mechanical and chemical weathering at the Earths surface.Lower Antelope Canyon was carved out of the surrounding sandstone by both mechanical weathering and chemical weathering. Wind, sand, and water from flash flooding are the primary weathering agents.Lower Antelope Canyon was carved out of the surrounding sandstone by both mechanical weathering and chemical weathering. Wind, sand, and water from flash flooding are the primary weathering agents.
Mechanical weathering is the breakdown of rock into particles without producing changes in the chemical composition of the minerals in the rock. Ice is the most important agent of mechanical weathering. Water percolates into cracks and fissures within the rock, freezes, and expands. The force exerted by the expansion is sufficient to widen cracks and break off pieces of rock. Heating and cooling of the rock, and the resulting expansion and contraction, also aids the process. Mechanical weathering contributes further to the breakdown of rock by increasing the surface area exposed to chemical agents.Chemical weathering is the breakdown of rock by chemical reaction. In this process the minerals within the rock are changed into particles that can be easily carried away. Air and water are both involved in many complex chemical reactions. The minerals in igneous rocks may be unstable under normal atmospheric conditions, those formed at higher temperatures being more readily attacked than those which formed at lower temperatures. Igneous rocks are commonly attacked by water, particularly acid or alkaline solutions, and all of the common igneous rock forming minerals with the exception of quartz which is very resistant are changed in this way into clay minerals and chemicals in solution.Rock particles in the form of clay, silt, sand, and gravel, are transported by the agents of erosion usually water, and less frequently by ice and wind to new locations and redeposited in layers, generally at a lower elevation.These agents reduce the size of the particles, sort them by size, and then deposit them in new locations. The sediments dropped by streams and rivers form alluvial fans, flood plains, deltas, and on the bottom of lakes and the sea floor. The wind may move large amounts of sand and other smaller particles. Glaciers transport and deposit great quantities of usually unsorted rock material as till.These deposited particles eventually become compacted and cemented together, forming clastic sedimentary rocks. Such rocks contain inert minerals which are resistant to mechanical and chemical breakdown such as quartz, zircon, rutile, and magnetite. Quartz is one of the most mechanically and chemically resistant minerals.edit OrganicOutcrop of Ordovician oil shale kukersite, northern Estonia.Outcrop of Ordovician oil shale kukersite, northern Estonia.Organic sedimentary rocks contain materials generated by living organisms, and include carbonate minerals created by organisms, such as corals, mollusks, and foraminifera, which cover the ocean floor with layers of calcite which can later form limestone. Other examples include stromatolites, the flint nodules found in chalk which is itself a biochemical sedimentary rock, a form of limestone, and coal and oil shale derived from the remains of tropical plants and subjected to pressure.
Chemical
Chemical sedimentary rocks form when mineral solutions, such as sea watr, evaporate. Examples include the evaporite minerals halite rock salt and gypsum.edit Economic and scientific relevanceSedimentary rocks are economically important in that they can easily be used as construction material because they are soft and easy to cut. For example, the White House in Washington DC is made of sandstone. In addition, sedimentary rocks often form porous and permeable reservoirs in sedimentary basins in which petroleum and other hydrocarbons can be found see Bituminous rocks.It is believed that the relatively low levels of carbon dioxide in the Earths atmosphere, in comparison to that of Venus, is because of large amounts of carbon being trapped in limestone and dolomite sedimentary layers. The flux of carbon from eroded sediments to marine deposits is part of the carbon cycle.The shape of the particles in sedimentary rocks has an important effect on the ability of microorganisms to colonize them. This interaction is studied in the science of geomicrobiology. One measure of the shape of these particles is the roundness factor, also known as the Krumbein number after the geologist W. C. Krumbein.oil organic matter Main article Soil organic matterSoil is mainly composed of minerals and organic matter, like decaying plants and animals, as well as living organisms. The minerals are derived from the weathering of parent material bedrock and overlying subsoil. The organic matter in soil derives from plants and animals. In a forest, for example, leaf litter and woody material falls to the forest floor. This is sometimes referred to as organic material. When it decays to the point it is no longer recognizable it is called soil organic matter. When the organic matter has broken down into a stable humic substances that resist further decomposition it is called humus. Thus soil organic matter comprises all of the organic matter in the soil exclusive of the undecayed material.edit Once living matterOrganic matter may refer to matter which was once part of a living organism or produced by a living organism. This definition is synonymous with biotic material, and would include a clams shell and naturally produced urea, while excluding synthetically produced urea. While this definition is useful for modeling nutrient flows, it is not useful in measuring the organic content of soil.edit DecayOrganic matter may be defined as material that is capable of decay, or the product of decay humus, or both. Usually the matter will be the remains of recently living organisms, and may also include stillliving organisms. Polymers and plastics, although they may be organic compounds, are usually not considered organic material, due to their poor ability to decompose. A clams shell, while biotic, would not be considered organic matter by this definition because of its inability to decay.
Organic chemistryMeasurements of organic matter generally measure only organic compounds or carbon, and so are only an approximation of the level of onceliving or decomposed matter. Some definitions of organic matter likewise only consider organic matter to refer to only the carbon content, or organic compounds, and do not consider the origins or decomposition of the matter. In this sense, not all organic compounds are created by living organisms, and living organisms do not only leave behind organic material. A clams shell, for example, while biotic, does not contain much organic carbon, so may not be considered organic matter in this sense. Conversely, urea is one of many organic compounds that can be synthesized without any biological activity.edit VitalismThe equation of organic with living organisms comes from the nowabandoned idea of vitalism that attributed a special force to life that alone could create organic substances. This idea was first questioned after the abiotic synthesis of urea by Friedrich Wöhler in .heoryiagram showing the net effect of symmetrical polar bonds direction of yellow arrows show the migration of electrons within boron trifluoride cancelling out to give a net polarity of zero. d shows an increase in negative charge and d+ shows an increase in positive charge.Diagram showing the net effect of symmetrical polar bonds direction of yellow arrows show the migration of electrons within boron trifluoride cancelling out to give a net polarity of zero. d shows an increase in negative charge and d+ shows an increase in positive charge.Electrons are not always shared equally between two bonding atoms one atom might exert more of a force on the electron cloud than the other. This pull is termed electronegativity and measures the attraction for electrons a particular atom has. The unequal sharing of electrons within a bond leads to the formation of an electric dipole a separation of positive and negative electric charge.Atoms with high electronegativities such as fluorine, oxygen, and nitrogen exert a greater pull on electrons than atoms with lower electronegativities. In a bonding situation this can lead to unequal sharing of electrons between atoms as electrons will spend more time closer to the atom with the higher electronegativity.Bonds can fall between one of two extremes being completely nonpolar or completely polar. A completely nonpolar bond occurs when the electronegativities are identical and therefore possess a difference of zero. A completely polar bond is more correctly termed ionic bonding and occurs when the difference between electronegativities is large enough that one atom takes an electron from the other. The terms polar and nonpolar bonds usually refer to covalent bonds. To determine the polarity of a covalent bond using numerical means, the difference between the electronegativity of the atoms is taken. If the result is between . and . then, generally, the bond is polar covalent.
Polarity of molecules
This section may require cleanup to meet Wikipedias quality standards.Please improve this article if you can. April Polarity of the hydrogen halide molecules, HX. From the top, HF, HCl, HBr and HI. Electronegativity decreases from F to I, thus polarity decreases from HF to HIPolarity of the hydrogen halide molecules, HX. From the top, HF, HCl, HBr and HI. Electronegativity decreases from F to I, thus polarity decreases from HF to HIA compound is composed of one or more chemical bonds between different atoms. The polarity of each bond within the compound may determine the overall polarity of the compound how polar or nonpolar it is.A polar molecule may be polar as a result of polar bonds or as a result of an asymmetric arrangement of nonpolar bonds and non bonding pairs of electrons.Example . A polar molecule by virtue of polar bonds bonds which have unequal sharing of electrons between the two atoms involved in bonding, e.g hydrogen fluoride, HF, where the bonding pair of electron is displaced towards the more electronegative fluorine atom.Example . In ammonia, NH, the three NH bonds have only a slight polarity towards the more electronegative nitrogen atom, however the lone pair of electrons pointing towards the fourth apex of the approximate tetrahedron, VSEPR is electron rich and results in a powerful dipole across the whole ammonia molecule.A nonpolar compound may be non polar because there is almost no polarity in the bonds or because of the symmetrical arrangement of polar bonds.Example . Methane, CH The four CH bonds, arranged tetrahedrally around the carbon atom, has polarity in the bonds though not very strong. However, the bonds are arranged symmetrically so there is no overall dipole in the molecule.Example . BF, boron trifluoride has a trigonal planar arrangement of three polar bonds at o This results in no overall dipole in the molecule.Example . Oxygen molecule, O, does not have polarity in the covalent bond hence there is n polarity in the molecule.dit Properties and examplesWhile the molecules can be described as polar, nonpolar, or semipolar, it must be noted that this is often a relative term, with one molecule simply being more polar or more nonpolar than another. However, the following properties are typical of such molecules.edit Polar moleculesExamples of household polar molecules include sugar sucrose. Polar molecules are generally able to dissolve in water HO due to the polar nature of water.Polar molecules have slightly positive and ightly negatively charged ends.edit Nonpolar moleculesA nonpolar compound occurs when there is an equal sharing of electrons between two different atoms. Examples of household nonpolar compounds include fats, oil and petrolgasoline. Therefore, most nonpolar molecules are water insoluble hydrophobic at room temperature. However many nonpolar organic solvents, such as turpentine, are able to dissolve nonpolar substances. When comparing a polar and nonpolar molecule with similar molar masses, the polar molecule generally has a higher boiling point, because of the dipoledipole interaction between their molecules. The most common form of such an interaction is the hydrogen bond.
Seafloor hydrothermal circulationHydrothermal circulation in the oceans is the passage of the water through mid-oceanic ridge systems.The term includes both the circulation of the well known, high temperature vent waters near the ridge crests, and the much lower temperature, diffuse flow of water through sediments and buried basalts further from the ridge crests. The former circulation type is sometimes termed "active", and the latter "passive". In both cases the principle is the same: cold dense seawater sinks into the basalt of the seafloor and is heated at depth whereupon it rises back to the rock-ocean water interface due to its lesser density. The heat source for the active vents is the newly formed basalt, and, for the highest temperature vents, the underlying magma chamber. The heat source for the passive vents is the still-cooling older basalts. Heat flow studies of the seafloor suggest that basalts within the oceanic crust take millions of years to completely cool as they continue to support passive hydrothermal circulation systems.Hydrothermal vents are locations on the seafloor where hydrothermal fluids mix into the overlying ocean. Perhaps the best known vent forms are the chimneys referred to as black smokers.[edit] Volcanic and magma related hydrothermal circulationHydrothermal circulation is not limited to ocean ridge environments. The source water for geysers and hot springs is heated groundwater convecting below and lateral to the hot water vent. Hydrothermal circulating convection cells exist any place an anomalous source of heat, such as an intruding magma or volcanic vent, comes into contact with the groundwater system.
