1.
Sedimentary
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Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
2.
Point Lobos
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Point Lobos is just south of Carmel-by-the-Sea, California, United States, at the north end of the Big Sur coast of the Pacific Ocean. Point Lobos contains a number of hiking trails, many next to the ocean, and it is the site of a historic marine reserve, which was expanded in 2007. It is also the home to a museum on whaling, which includes a building once used by area fishermen. The longstanding wildlife protection and scenic seascape have led to Point Lobos reputation as a local recreational scuba diving destination. The parks origins are owed to engineer Alexander Allan, who purchased a parcel of land in 1933 to prevent it from being developed. It was to be subdivided into 1,000 lots under the name of Carmelito, the iconic Point Lobos area is geologically unique and contains a rich and diverse plant and animal life both on shore and in the water. Called the greatest meeting of land and water in the world by landscape artist Francis McComas, the geological history of Point Lobos describes the rocks that create the headlands and inlets that make Point Lobos famous. Carmel submarine canyon lies just north of Point Lobos, like Monterey Canyon to the north the canyon provides cold, nutrient-rich water to the surface during upwelling events. These nutrient rich waters fuel the high primary productivity seen in Carmel and Monterey Bays, the original Point Lobos Ecological Reserve was created in 1973. As one of Californias oldest and best known no-take reserves, its large, in 2007, the Ecological Reserve was expanded and renamed with the establishment of The Point Lobos SMR and Point Lobos SMCA by the California Department of Fish and Game. Point Lobos SMR covers 5.36 square miles, the SMR protects all marine life within its boundaries. Fishing and take of all living marine resources is prohibited, the marine reserve is bounded by the mean high tide line and straight lines connecting the following points in the order listed, 36°31. 70’ N. lat. 121°55. 55’ W. long. 36°31. 70’ N. lat. 121°58. 25’ W. long, 36°28. 88’ N. lat. 121°58. 25’ W. long. And 36°28. 88’ N. lat. 121°56. 30’ W. long, Point Lobos SMCA covers 8.83 square miles. Harvest of all living marine resources is prohibited in the area except the recreational and commercial take of salmon, albacore. The area is bounded by lines connecting the following points in the order listed except where noted. 36°31. 70’ N. lat. 122°01. 30’ W. long, thence southward along the three nautical mile offshore boundary to 36°28. 88’ N. lat. 122°00. 55’ W. long. 36°28. 88’ N. lat. 121°58. 25’ W. long, and 36°31. 70’ N. lat. 121°58. 25’ W. long
3.
Clastic rock
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Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, clastic sedimentary rocks are rocks composed predominantly of broken pieces or clasts of older weathered and eroded rocks. Clastic sediments or sedimentary rocks are classified based on size, clast and cementing material composition. The classification factors are often useful in determining a samples environment of deposition, an example clastic environment would be a river system in which the full range of grains being transported by the moving water consist of pieces eroded from solid rock upstream. Grain size varies from clay in shales and claystones, through silt in siltstones, sand in sandstones, the Krumbein phi scale numerically orders these terms in a logarithmic size scale. Siliciclastic rocks are clastic rocks that are composed almost exclusively of silicon. The composition of sedimentary rocks includes the chemical and mineralogical components of the framework as well as the cementing material that make up these rocks. Boggs divides them into four categories, major minerals, accessory minerals, rock fragments, major minerals can be categorized into subdivisions based on their resistance to chemical decomposition. Those that possess a great resistance to decomposition are categorized as stable, while those that do not are considered less stable, the most common stable mineral in siliciclastic sedimentary rocks is quartz. Quartz makes up approximately 65 percent of framework grains present in sandstones, less stable minerals present in this type of rocks are feldspars, including both potassium and plagioclase feldspars. Feldspars comprise a considerably lesser portion of framework grains and minerals and they only make up about 15 percent of framework grains in sandstones and 5% of minerals in shales. Clay mineral groups are present in mudrocks but can be found in other siliciclastic sedimentary rocks at considerably lower levels. Accessory minerals are associated with those whose presence in the rock are not directly important to the classification of the specimen and these generally occur in smaller amounts in comparison to the quartz, and feldspars. Furthermore, those that do occur are generally heavy minerals or coarse grained micas, rock fragments also occur in the composition of siliciclastic sedimentary rocks and are responsible for about 10 -15 percent of the composition of sandstone. They generally make up most of the gravel size particles in conglomerates, though they sometimes are, rock fragments are not always sedimentary in origin. They can also be metamorphic or igneous, chemical cements vary in abundance but are predominantly found in sandstones. The two major types, are based and carbonate based
4.
Sedimentary rock
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Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
5.
Gravel
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Gravel /ˈɡrævəl/ is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel is categorized by the Udden-Wentworth scale into granular gravel and pebble gravel, one cubic metre of gravel typically weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications, many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac, both sand and small gravel are also important for the manufacture of concrete. Large gravel deposits are a geological feature, being formed as a result of the weathering. The action of rivers and waves tends to pile up gravel in large accumulations and this can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the deposition of gravel in the region during the Ice Ages. As of 2006, the United States is the leading producer and consumer of gravel. The word gravel comes from the Breton language, adding the -el suffix in Breton denotes the component parts of something larger. Thus gravel means the stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravele or gravelle, Gravel often has the meaning a mixture of different size pieces of stone mixed with sand and possibly some clay. American English also allows small stones without sand mixed in also known as crushed stone, types of gravel include, Bank gravel, naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as Bank run or River run, bench gravel, a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. Creek rock, this is rounded, semi-polished stones, potentially of a wide range of types. It is also used as concrete aggregate and less often as a paving surface. Crushed stone, rock crushed and graded by screens and then mixed to a blend of stones and fines and it is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, also known as crusher run, DGA QP, and shoulder stone
6.
Pebble
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A pebble is a clast of rock with a particle size of 2 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered larger than granules and smaller than cobbles, a rock made predominantly of pebbles is termed a conglomerate. Pebble tools are among the earliest known man-made artifacts, dating from the Palaeolithic period of human history, a beach composed chiefly of surface pebbles is commonly termed a shingle beach. This type of beach has armoring characteristics with respect to wave erosion, as well as ecological niches that provide habitat for animals and plants. Inshore banks of shingle exist in locations, such as the entrance to the River Ore. Pebbles come in colors and textures and can have streaks, known as veins. Pebbles are mostly smooth but, dependent on how frequently they come in contact with the sea, pebbles left above the high water mark may have growths of organisms such as lichen on them, signifying the lack of contact with seawater. Pebbles are found in two locations – on the beaches of various oceans and seas, and inland where ancient seas used to cover the land, when then the seas retreated, the rocks became landlocked. They can also be found in lakes and ponds, pebbles can also form in rivers, and travel into estuaries where the smoothing continues in the sea. Beach pebbles and river pebbles are distinct in their geological formation, beach pebbles form gradually over time as the ocean water washes over loose rock particles. The result is a smooth, rounded appearance, the typical size range is from 2 mm to 50 mm. The colors range from translucent white to black, and include shades of yellow, brown, red and green. Some of the more plentiful pebble beaches are found along the coast of the Pacific Ocean, beginning in the United States and extending down to the tip of South America in Argentina. Other pebble beaches are found in northern Europe, along the coast of the U. K. and Ireland, on the shores of Australia, inland pebbles are usually found along the shores of large rivers and lakes. These pebbles form as the water washes over rock particles on the bottom. The smoothness and color of river pebbles depends on several factors, such as the composition of the soil of the banks, the chemical characteristics of the water. Because river current is gentler than the waves, river pebbles are usually not as smooth as beach pebbles. The most common colors of rock are black, grey, green, brown
7.
Cobble (geology)
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A cobble is a clast of rock defined on the Udden–Wentworth scale as having a particle size of 64–256 millimeters, larger than a pebble and smaller than a boulder. Other scales define a cobbles size in different terms. A rock made predominantly of cobbles is termed a conglomerate, cobblestone is a building material based on cobbles. Cobbles, also called cobblestones, derive their name from the word cob, the term is further related to the German Kopf, meaning head. Chester Wentworth referred to cobbles as cobble bowlders in his 1922 paper that would become the basis for the Udden–Wentworth scale, within the widely used Krumbein phi scale of grain sizes, cobbles are defined as clasts of rock ranging from −6 to −8 φ. This classification corresponds with the Udden–Wentworth size scale which defines cobbles as clasts with diameters from 64–256 millimeters, on this scale, cobbles are larger than pebbles which measure 4–64 millimeters in diameter and smaller than boulders, whose diameters range from 256–4,096 millimeters. On the Udden–Wentworth scale, a fraction of cobbles is classified as gravel while a lithified sample primarily composed of cobbles is a conglomerate. The Committee on Sedimentation of the US National Research Council has recommended that in situ cobbles be identified by their process of origination, various attempts have been made to refine the Udden–Wentworth scale, including its definition of cobbles. In 1968, D. J. Doeglas proposed subdividing the cobble designation into two fractions, small cobbles and large cobbles and they proposed defining fine cobbles as those with diameters from 64–128 millimeters and coarse cobbles as those with diameters from 128–256 millimeters. When occurring in streams, cobbles are likely to be found in mountain valley streambeds that are moderately steep, cobbles are also transported by glaciers and deposited as with other grades of sediment as till. If the till is water-laid, finer particles like sand and pebbles may be washed away, leaving a deposit of only boulders. Glacially transported cobbles tend to share several identifying features including a tabular shape, cobble conglomerates may be alluvial in origin or the product of stone avalanches, a type of debris flow resulting from unconsolidated cobbles and gravel. In such stone avalanches, well-rounded cobbles may travel the farthest on account of their low rolling friction, when the product of alluvial processes, the cobble conglomerates matrix consists of gravel and coarse sand. In contrast, the matrices of flow-deposited conglomerates are primarily mud, bunte, K. Abt, S. R. Sampling Surface and Subsurface Particle-Size Distributions in Wadable Gravel- and Cobble-Bed Streams for Analyses in Sediment Transport, Hydraulics, and Streambed Monitoring. Fort Collins, CO, United States Forest Service, hsü, K. J. Physics of Sedimentology, Textbook and Reference. New York City, Harper and Row
8.
Boulder
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In geology, a boulder is a rock fragment with size greater than 25.6 centimetres in diameter. Smaller pieces are called cobbles and pebbles, while a boulder may be small enough to move or roll manually, others are extremely massive. In common usage, a boulder is too large for a person to move, smaller boulders are usually just called rocks or stones. The word boulder is short for boulder stone, from Middle English bulderston or Swedish bullersten, in places covered by ice sheets during Ice Ages, such as Scandinavia, northern North America, and Siberia, glacial erratics are common. Erratics are boulders picked up by ice sheets during their advance and they are called erratic because they typically are of a different rock type than the bedrock on which they are deposited. One of them is used as the pedestal of the Bronze Horseman in Saint Petersburg, boulder sized clasts are found in some sedimentary rocks, such as coarse conglomerate and boulder clay. The climbing of large boulders is called bouldering, road debris Monolith Media related to Boulders at Wikimedia Commons
9.
Consolidation (soil)
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Consolidation is a process by which soils decrease in volume. According to Karl von Terzaghi consolidation is any process which involves a decrease in water content of saturated soil without replacement of water by air, in general it is the process in which reduction in volume takes place by expulsion of water under long term static loads. It occurs when stress is applied to a soil causes the soil particles to pack together more tightly. When this occurs in a soil that is saturated with water, water will be squeezed out of the soil, the magnitude of consolidation can be predicted by many different methods. In the Classical Method, developed by Terzaghi, soils are tested with an oedometer test to determine their compression index and this can be used to predict the amount of consolidation. When stress is removed from a soil, the soil will rebound. If the stress is reapplied, the soil will consolidate again along a recompression curve, the soil which had its load removed is considered to be overconsolidated. This is the case for soils which have previously had glaciers on them, the highest stress that it has been subjected to is termed the preconsolidation stress. The over consolidation ratio or OCR is defined as the highest stress experienced divided by the current stress, a soil which is currently experiencing its highest stress is said to be normally consolidated and to have an OCR of one. A soil could be considered underconsolidated immediately after a new load is applied, the process of consolidation is often explained with an idealized system composed of a spring, a container with a hole in its cover, and water. In this system, the spring represents the compressibility or the structure of the soil itself, the container is completely filled with water, and the hole is closed. A load is applied onto the cover, while the hole is still unopened, at this stage, only the water resists the applied load. As soon as the hole is opened, water starts to drain out through the hole, after some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load and this method assumes consolidation occurs in only one-dimension. Laboratory data is used to construct a plot of strain or void ratio versus effective stress where the stress axis is on a logarithmic scale. The plots slope is the index or recompression index. The equation for consolidation settlement of a consolidated soil can then be determined to be. E0 is the void ratio
10.
Sediment
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For sediment in beverages, see dregs. For example, sand 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 also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also 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, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers 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, dunes, 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
11.
Sand
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Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt, Sand can also refer to a textural class of soil or soil type, i. e. a soil containing more than 85% sand-sized particles by mass. The second most common type of sand is calcium carbonate, for example aragonite, 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, and sand suitable for making concrete is in high demand, 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 size is termed a sand grain. Sand grains are between gravel and silt, a 1953 engineering standard published by the American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A1938 specification of the United States Department of Agriculture was 0.05 mm. Sand feels gritty when rubbed between the fingers. ISO14688 grades sands as fine, medium 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 commonly divided into five sub-categories based on size, very fine sand, fine sand, medium sand, coarse sand, and very 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 composition of sand is highly variable, depending on the local rock sources. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a granitic rock outcrop. Some sands contain magnetite, chlorite, 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 typically green in color, as are sands derived from basaltic with a high olivine content, many sands, especially 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, the study of individual grains can reveal much historical information as to the origin and kind of transport of the grain. Quartz sand that is weathered from granite or gneiss quartz crystals will be angular. It is called grus in geology or sharp sand in the trade where it is preferred for concrete. Sand that is transported long distances by water or wind will be rounded, people who collect sand as a hobby are known as arenophiles
12.
Silt
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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 in a body of such as a river. It may also exist as soil deposited at the bottom of a water body, Silt has a moderate specific area with a typically non-sticky, plastic feel. Silt usually has a floury feel when dry, and a slippery feel when wet, Silt can be visually observed with a hand lens. Silt is created by a variety of physical processes capable of splitting the generally sand-sized quartz crystals of primary rocks by exploiting deficiencies in their lattice and these involve chemical weathering of rock and regolith, and 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 it is in semi-arid environments that substantial quantities of silt are produced. Silt is sometimes known as rock flour or stone dust, especially produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar, sedimentary rock composed mainly of silt is known as siltstone. Liquefaction created by an earthquake is silt suspended in water that is 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, ISO14688 grades silts between 0.002 mm and 0.063 mm. In actuality, silt is chemically distinct from clay, and unlike clay, grains of silt are approximately the size in all dimensions, furthermore. Clays are formed from thin plate-shaped particles held together by electrostatic forces, 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 Food and 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 easily 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 streams or 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. In south east Bangladesh, in the Noakhali district, cross dams were built in the 1960s whereby silt gradually started forming new land called chars, the district of Noakhali has gained more than 28 square miles of land in the past 50 years
13.
Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
14.
Matrix (geology)
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The matrix or groundmass of rock is the finer-grained mass of material wherein larger grains, crystals or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic and this porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix, also in South Africa, diamonds are often mined from a matrix of weathered clay-like rock called yellow ground. The matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt and it also used to describe the rock material in which a fossil is embedded. All sediments are at first in an incoherent condition, and in this state they may remain for an indefinite period. Millions of years have elapsed since some of the early Tertiary strata gathered on the floor, yet they are quite friable. The pressure of newer sediments on underlying masses is one cause of this change. More efficiency is generally ascribed to the action of percolating water, the redeposited cementing material is most commonly calcareous or siliceous. Limestones, which were originally a loose accumulation of shells, corals, the change of aragonite to calcite and of calcite to dolomite, by forming new crystalline masses in the interior of the rock, usually also accelerates consolidations. Silica is less soluble in ordinary waters, but even this ingredient of rocks is dissolved and redeposited with great frequency. Others contain fine scales of kaolin or of mica, argillaceous materials may be compacted by mere pressure, like graphite and other scaly minerals
15.
Calcium carbonate
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Calcium carbonate is a chemical compound with the formula CaCO3. It is a substance found in rocks as the minerals calcite and aragonite and is the main component of pearls and the shells of marine organisms, snails. Calcium carbonate is the ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a supplement or as an antacid. Calcium carbonate shares the properties of other carbonates. CaCO3 + CO2 + H2O → Ca2 This reaction is important in the erosion of rock, forming caverns. An unusual form of calcium carbonate is the hexahydrate, ikaite, ikaite is stable only below 6 °C. The vast majority of calcium used in industry is extracted by mining or quarrying. Pure calcium carbonate, can be produced from a quarried source. Alternatively, calcium carbonate is prepared from calcium oxide, other forms can be prepared, the denser, orthorhombic λ-CaCO3 and μ-CaCO3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures above 85 °C, calcite contains calcium atoms coordinated by 6 oxygen atoms, in aragonite they are coordinated by 9 oxygen atoms. The vaterite structure is not fully understood, magnesium carbonate MgCO3 has the calcite structure, whereas strontium and barium carbonate adopt the aragonite structure, reflecting their larger ionic radii. Calcite, aragonite and vaterite are pure calcium carbonate minerals, industrially important source rocks which are predominantly calcium carbonate include limestone, chalk, marble and travertine. Eggshells, snail shells and most seashells are predominantly calcium carbonate, oyster shells have enjoyed recent recognition as a source of dietary calcium, but are also a practical industrial source. While not practical as a source, dark green vegetables such as broccoli. Beyond Earth, strong evidence suggests the presence of Calcium carbonate on Mars, signs of Calcium Carbonate have been detected at more than one location. This provides some evidence for the past presence of liquid water, Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite, calcite and dolomite, the carbonate minerals form the rock types, limestone, chalk, marble, travertine, tufa, and others
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Iron oxide
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Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides, common rust is a form of iron oxide. Iron oxides are used as inexpensive, durable pigments in paints, coatings. Colors commonly available are in the end of the yellow/orange/red/brown/black range. When used as a coloring, it has E number E172. Limonite Iron oxide nanoparticles List of inorganic pigments Information from Nano-Oxides, http, //chemed. chem. purdue. edu/demos/demosheets/12.3. html http, //minerals. usgs. gov/minerals/pubs/commodity/iron_oxide/ CDC - NIOSH Pocket Guide to Chemical Hazards de
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Sedimentary structures
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Sedimentary structures are those structures formed during sediment deposition. There are two kinds of structures, bidirectional and unidirectional. Flow regimes in single-direction flow, which at varying speeds and velocities produce different structures, are called bedforms, in the lower flow regime, the natural progression is from a flat bed, to some sediment movement, to ripples, to slightly larger dunes. Dunes have a vortex in the lee side of the dune, as the upper flow regime forms, the dunes become flattened out, and then produce antidunes. At higher still velocity, the antidunes are flattened and most sedimentation stops, ripple marks usually form in conditions with flowing water, in the lower part of the Lower Flow Regime. There are two types of marks, Symmetrical ripple marks - Often found on beaches, they are created by a two way current, for example the waves on a beach. This creates ripple marks with pointed crests and rounded troughs, which arent inclined more to a certain direction, three common sedimentary structures that are created by these processes are herringbone cross-stratification, flaser bedding, and interference ripples. Asymmetrical ripple marks - These are created by a one way current, for example in a river and this creates ripple marks with still pointed crests and rounded troughs, but which are inclined more strongly in the direction of the current. For this reason, they can be used as palaeocurrent indicators, antidunes are the sediment bedforms created by fast, shallow flows of water with a Froude number greater than 1. Antidunes form beneath standing waves of water that periodically steepen, migrate, the antidune bedform is characterized by shallow foresets, which dip upstream at an angle of about ten degrees that can be up to five meters in length. They can be identified by their low angle foresets, for the most part, antidunes bedforms are destroyed during decreased flow, and therefore cross bedding formed by antidunes will not be preserved. A number of biologically-created sedimentary structures exist, called trace fossils, examples include burrows and various expressions of bioturbation. Ichnofacies are groups of fossils that together help give information on the depositional environment. In general, as deeper burrows become more common, the shallower the water, as surface traces become more common, the water becomes deeper. Microbes may also interact with sediment to form Microbially Induced Sedimentary Structures, soft-sediment deformation structures or SSD, is a consequence of the loading of wet sediment as burial continues after deposition. The heavier sediment squeezes the water out of the sediment due to its own weight. There are three variants of SSD, load structures or load casts are blobs that form when a denser, wet sediment slumps down on. Pseudonodules or ball-and-pillow structures, are pinched-off load structures, these may also be formed by earthquake energy, flame structures, fingers of mud that protrude into overlying sediments
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Cross-bedding
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In geology, the sedimentary structures known as cross-bedding are the horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, cross-beds or sets are the groups of inclined layers, and the inclined layers are known as cross strata. Cross bedding forms during deposition on the surfaces of bedforms such as ripples and dunes. Examples of these bedforms are ripples, dunes, anti-dunes, sand waves, hummocks, bars, Cross-bedding is widespread in many environments. Environments in which movement is fast enough and deep enough to develop large-scale bed forms fall into three natural groupings, rivers, tide-dominated coastal and marine settings. Cross beds can tell much about what an area was like in ancient times. The direction the beds are dipping indicates paleocurrent, the direction of sediment transport. The type and condition of sediments can tell geologists the type of environment, studying modern analogs allows geologists to draw conclusions about ancient environments. Paleocurrent can be determined by seeing a cross-section of a set of cross-beds, however, to get a true reading, the axis of the beds must be visible. It is also difficult to distinguish between the beds of a dune and the cross beds of an antidune. This could lead to misinterpretation since dunes dip downstream while antidunes dip upstream, the direction of motion of the cross-beds can show ancient flow or wind directions. The foresets are deposited at the angle of repose, so geologists are able to measure dip direction of the cross-bedded sediments, however, most cross-beds are not tabular, they are troughs. Since troughs can give a 180 degree variation of the dip of foresets, in this case, true paleocurrent direction is determined by the axis of the trough. Paleocurrent direction is important in reconstructing past climate and drainage patterns, sand dunes preserve the prevalent wind directions, Cross-bedding is formed by the downstream migration of bedforms such as ripples or dunes in a flowing fluid. The fluid flow causes sand grains to saltate up the side of the bedform. At this point, the crest of granular material has grown too large and will be overcome by the force of the depositing fluid, repeated avalanches will eventually form the sedimentary structure known as cross-bedding, with the structure dipping in the direction of the paleocurrent. The angle and direction of cross-beds are generally fairly consistent, individual cross-beds can range in thickness from just a few tens of centimeters, up to hundreds of feet or more depending upon the depositional environment and the size of the bedform. Cross-bedding can form in any environment in which a fluid flows over a bed with mobile material and it is most common in stream deposits, tidal areas, and in aeolian dunes
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Graded bedding
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In geology, a graded bed is one characterized by a systematic change in grain or clast size from the base of the bed to the top. Most commonly this takes the form of grading, with coarser sediments at the base. Normally graded beds generally represent depositional environments which decrease in energy as time passes. They are perhaps best represented in turbidite strata, where they indicate a strong current that deposits heavy, coarse sediments first. They can also form in terrestrial stream deposits, in reverse or inverse grading the bed coarsens upwards. This type of grading is relatively uncommon but is characteristic of sediments deposited by grain flow and it is also observed in eolian ripples. These deposition processes are examples of granular convection, graded bedding is a sorting of particles according to clast size and shape on a lithified horizontal plane. The term is an explanation as to how a geologic profile was formed, stratification on a lateral plane is the physical result of active depositing of different size materials. Density and gravity forces in the movement of these materials in a confined system will result in a separating of the detritus settling with respect to size. This will result in dense, higher porosity clasts at the top and denser, less porous clasts consolidated on the bottom. Inversely graded beds are composed of large clasts on the top, grades of the bedding material are determined by precipitation of solid components compared to the viscosity of the medium in which the particles will precipitate from. Steno’s Principle of Original Horizontality explains that rock layers form in layers over an underdetermined time scale. Nicholas Steno first published his hypothesis in 1669 after recognizing that fossils were preserved in layers of rock, for materials to settle in stratified layers the defining quality is periodicity. There must be repeated depositional events with changes in precipitation of materials over time, the thickness of graded beds ranges from 1 millimeter to multiple meters. There is no set time limit in which the layers will be formed, uniformity of size and shape of materials within the bed form must be present on a present or previously horizontal plane. Weathering, the chemical or physical forces breaking apart the solid materials that will be potentially transported, erosion, The movement of material due to weathering forces that have freed materials for movement. Deposition, The material settles on a horizontal plane either through chemical or physical precipitation, note, The secondary processes of compaction, cementation, and lithification, help to hold a stratified bed in place. In aeolian or fluid environments, where there is a decrease in transport energy over time
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Breccia
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Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments. The word has its origins in the Italian language, in which it means either loose gravel or stone made by cemented gravel. A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia. Sedimentary breccia is a type of sedimentary rock which is made of angular to subangular. A conglomerate, by contrast, is a rock composed of rounded fragments or clasts of pre-existing rocks. Both breccia and conglomerate are composed of fragments averaging greater than 2 millimetres in size, the angular shape of the fragments indicates that the material has not been transported far from its source. Sedimentary breccia consists of angular, poorly sorted, immature fragments of rocks in a finer grained groundmass which are produced by mass wasting and it is lithified colluvium or scree. Thick sequences of sedimentary breccia are generally formed next to fault scarps in grabens, Breccia may occur along a buried stream channel where it indicates accumulation along a juvenile or rapidly flowing stream. Sedimentary breccia may be formed by debris flows. Turbidites occur as fine-grained peripheral deposits to sedimentary breccia flows, in a karst terrain, a collapse breccia may form due to collapse of rock into a sinkhole or in cave development. Fault breccia results from the action of two fault blocks as they slide past each other. Subsequent cementation of these fragments may occur by means of the introduction of mineral matter in groundwater. Volcanic pyroclastic rocks are formed by explosive eruption of lava and any rocks which are entrained within the eruptive column and this may include rocks plucked off the wall of the magma conduit, or physically picked up by the ensuing pyroclastic surge. Lavas, especially rhyolite and dacite flows, tend to form volcanic rocks by a process known as autobrecciation. This occurs when the thick, nearly solid lava breaks up into blocks, the resulting breccia is uniform in rock type and chemical composition. Lavas may also pick up rock fragments, especially if flowing over unconsolidated rubble on the flanks of a volcano, within the volcanic conduits of explosive volcanoes the volcanic breccia environment merges into the intrusive breccia environment. There the upwelling lava tends to solidify during quiescent intervals only to be shattered by ensuing eruptions, clastic rocks are also commonly found in shallow subvolcanic intrusions such as porphyry stocks, granites and kimberlite pipes, where they are transitional with volcanic breccias. Intrusive rocks can become brecciated in appearance by multiple stages of intrusion and this may be seen in many granite intrusions where later aplite veins form a late-stage stockwork through earlier phases of the granite mass
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Calcite
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Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of hardness, based on scratch hardness comparison. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite, aragonite will change to calcite at 380–470 °C, and vaterite is even less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime and it is thus etymologically related to chalk. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals, however, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms and it may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form and its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a gravity of 2.71. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes, acute scalenohedral crystals are sometimes referred to as dogtooth spar while the rhombohedral form is sometimes referred to as nailhead spar. Single calcite crystals display an optical property called birefringence and this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669, at a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in water, acidity can cause dissolution of calcite. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite, calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, high-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry
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Hematite
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Hematite, also spelled as haematite, is the mineral form of iron oxide, one of several iron oxides. Hematite crystallizes in the lattice system, and it has the same crystal structure as ilmenite. Hematite and ilmenite form a solid solution at temperatures above 950 °C. Hematite is colored black to steel or silver-gray, brown to reddish brown and it is mined as the main ore of iron. Varieties include kidney ore, martite, iron rose and specularite, while the forms of hematite vary, they all have a rust-red streak. Hematite is harder than iron, but much more brittle. Maghemite is a hematite- and magnetite-related oxide mineral, huge deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that can have still standing water or mineral hot springs, the mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. Hematite can also occur without water, however, usually as the result of volcanic activity, the name hematite is derived from the Greek word for blood αἷμα haima, due to the red coloration found in some varities of hematite. The color of hematite lends itself to use as a pigment, ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%. Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite, the principal use of ochre is for tinting with a permanent color. The red chalk writing of this mineral was one of the earliest in the history of humans, the powdery mineral was first used 164,000 years ago by the Pinnacle-Point man possibly for social purposes. Hematite residues are found in graves from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary red chalk mines have been found that are from 5000 BC, rich deposits of hematite have been found on the island of Elba that have been mined since the time of the Etruscans. Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment. The disappearance of the moment with a decrease in temperature at 260 K is caused by a change in the anisotropy which causes the moments to align along the c axis, in this configuration, spin canting does not reduce the energy. The magnetic properties of bulk hematite differ from their nanoscale counterparts, for example, the Morin transition temperature of hematite decreases with a decrease in the particle size. Two other end-members are referred to as protohematite and hydrohematite, enhanced magnetic coercivities for hematite have been achieved by dry-heating a 2-line ferrihydrite precursor prepared from solution
