1.
Geomorphology
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Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earths surface. Geomorphologists work within disciplines such as geography, geology, geodesy, engineering geology, archaeology. This broad base of interests contributes to many styles and interests within the field. Earths surface is modified by a combination of processes that sculpt landscapes, and geologic processes that cause tectonic uplift and subsidence. Many of these factors are strongly mediated by climate, the broad-scale topographies of the Earth illustrate this intersection of surface and subsurface action. Mountain belts are uplifted due to geologic processes, denudation of these high uplifted regions produces sediment that is transported and deposited elsewhere within the landscape or off the coast. On progressively smaller scales, similar ideas apply, where individual landforms evolve in response to the balance of additive processes, often, these processes directly affect each other, ice sheets, water, and sediment are all loads that change topography through flexural isostasy. Topography can modify the climate, for example through orographic precipitation. Many geomorphologists are particularly interested in the potential for feedbacks between climate and tectonics, mediated by geomorphic processes, in addition to these broad-scale questions, geomorphologists address issues that are more specific and/or more local. Fluvial geomorphologists focus on rivers, how they transport sediment, migrate across the landscape, cut into bedrock, respond to environmental and tectonic changes, and interact with humans. Soils geomorphologists investigate soil profiles and chemistry to learn about the history of a landscape and understand how climate, biota. Other geomorphologists study how hillslopes form and change, still others investigate the relationships between ecology and geomorphology. Because geomorphology is defined to comprise everything related to the surface of the Earth and its modification, geomorphologists use a wide range of techniques in their work. These may include fieldwork and field data collection, the interpretation of remotely sensed data, geochemical analyses, geomorphologists may rely on geochronology, using dating methods to measure the rate of changes to the surface. Practical applications of geomorphology include hazard assessment, river control and stream restoration, planetary geomorphology studies landforms on other terrestrial planets such as Mars. Indications of effects of wind, fluvial, glacial, mass wasting, meteor impact, tectonics and this effort not only helps better understand the geologic and atmospheric history of those planets but also extends geomorphological study of the Earth. Planetary geomorphologists often use Earth analogues to aid in their study of surfaces of other planets, other than some notable exceptions in antiquity, geomorphology is a relatively young science, growing along with interest in other aspects of the earth sciences in the mid-19th century. This section provides a brief outline of some of the major figures
2.
Groundwater
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Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is also withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is also evidence that water may also exist in the subsurface of Jupiters moon Europa. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
3.
Water table
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The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water, the water table is the surface where the water pressure head is equal to the atmospheric pressure. It may be visualized as the surface of the materials that are saturated with groundwater in a given vicinity. The groundwater may be from precipitation or from groundwater flowing into the aquifer, in areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths water fills in more of the spaces in the soils. Below the water table, in the zone, layers of permeable rock that yield groundwater are called aquifers. In less permeable soils, such as tight bedrock formations and historic lakebed deposits, the water table should not be confused with the water level in a deeper well. The elevation of the water in this well is dependent upon the pressure in the deeper aquifer and is referred to as the potentiometric surface. The water table may vary due to changes such as precipitation and evapotranspiration. Springs, rivers, lakes and oases occur when the table reaches the surface. Springs commonly form on hillsides, where the Earths slanting surface may intersect with the water table, Groundwater entering rivers and lakes accounts for the base-flow water levels in water bodies. Within an aquifer, the table is rarely horizontal, but reflects the surface relief due to the capillary effect in soils, sediments. In the aquifer, groundwater flows from points of pressure to points of lower pressure. The slope of the table is known as the hydraulic gradient, which depends on the rate at which water is added to and removed from the aquifer. This occurs when there is a layer of rock or sediment or relatively impermeable layer above the main water table/aquifer. If a perched aquifers flow intersects the Earths dry surface, at a wall for example. On low-lying oceanic islands with porous soil, freshwater tends to collect in lenticular pools on top of the denser seawater intruding from the sides of the islands, such an islands freshwater lens, and thus the water table, rises and falls with the tides. In some regions, for example, Great Britain or California, winter precipitation is higher than summer precipitation
4.
Beach
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A beach is a landform along a body of water. It usually consists of particles, which are often composed of rock, such as sand, gravel, shingle, pebbles. The particles comprising a beach are occasionally biological in origin, such as shells or coralline algae. Some beaches have man-made infrastructure, such as posts, changing rooms. They may also have hospitality venues nearby, wild beaches, also known as undeveloped or undiscovered beaches, are not developed in this manner. Wild beaches can be valued for their beauty and preserved nature. Beaches typically occur in areas along the coast where wave or current action deposits, although the seashore is most commonly associated with the word beach, beaches are also found by lakes and alongside large rivers. Beach may refer to, small systems where rock material moves onshore, offshore, or alongshore by the forces of waves and currents, the former are described in detail below, the larger geological units are discussed elsewhere under bars. There are several parts to a beach that relate to the processes that form. The part mostly above water, and more or less influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline, the berm has a crest and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, at some point the influence of the waves on the material comprising the beach stops, and if the particles are small enough, winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune and these geomorphic features compose what is called the beach profile. The beach profile changes seasonally due to the change in energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the profile is higher in summer. The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited, onshore winds carry it further inland forming and enhancing dunes. Conversely, the profile is lower in the storm season due to the increased wave energy. The removal of sediment from the berm and dune thus decreases the beach profile
5.
Gully
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A gully is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width, when the gully formation is in process, the water flow rate can be substantial, causing a significant deep cutting action into soil. The earliest known usage of the term is from 1657 and it originates from the French word goulet, a diminutive form of goule which means throat. It is possible that the term was derived from a type of knife at the time, gullying or gully erosion is the process by which gullies are formed. Hillsides are more prone to gullying when they are cleared of vegetation, through deforestation, the eroded soil is easily carried by the flowing water after being dislodged from the ground, normally when rainfall falls during short, intense storms such as during thunderstorms. A gully may grow in length by means of erosion at a knick point. This erosion can result from interflow as well as surface runoff, gullies reduce the productivity of farmland where they incise into the land, and produce sediment that may clog downstream waterbodies. Because of this, much effort is invested into the study of gullies within the scope of geomorphology, in the prevention of gully erosion, the total soil loss from gully formation and subsequent downstream river sedimentation can be sizeable. Gullies can be formed or enlarged by a number of human activities, artificial gullies are formed during hydraulic mining when jets or streams of water are projected onto soft alluvial deposits to extract gold or tin ore. The remains of mining methods are very visible landform features in old goldfields such as in California. The badlands at Las Medulas for example, were created during the Roman period by hushing or hydraulic mining of the gold-rich alluvium with water supplied by numerous aqueducts tapping nearby rivers, each aqueduct produced large gullies below by erosion of the soft deposits. The effluvium was carefully washed with smaller streams of water to extract the nuggets, gullies are widespread at mid- to high latitudes on the surface of Mars, and are some of the youngest features observed on that planet, probably forming within the last few 100,000 years. Flow as springs from deeper seated liquid water aquifers in the subsurface is also a possible explanation for the formation of some Martian gullies. Arroyo Coulee Couloir Canyon Gulch Ravine Wadi Lavaka Badlands Rill Oxford English Dictionary
6.
Lavaka
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Lavaka, the Malagasy word for hole, usually found on the side of a hill, is a type of erosional feature common in Madagascar. Lavakas form where these hard laterites overlie thick saprolite, on slopes, in areas that have a hot dry season. They are a type of gully, formed via groundwater sapping and they are usually shaped like a tear-drop with a steep, round headwall that narrows downhill into a shallow outlet channel. Although human activities—such as deforestation, overgrazing, road creation, and grassland burning—can contribute to lavaka formation, among the natural controls on lavaka formation are the amount of seismic activity in the region, the topographic relief, and hydraulic conductivity of materials in the saprolite. For instance, earthquakes in the region can cause cracks in the hard, upper layer of laterite, lavakas can often cause a lot of damage to nearby communities. During the monsoon season, heavy rains carry away all the material from the lavaka. This is the basis for much of the recent research that has conducted on the variables involved in lavaka formation. The term lavaka entered the international geography / geology vocabulary following the work of Riquier, cox, R. Bierman, P. Jungers, M. C. and Rakotondrazafy, A. F. M. 2009, Erosion rates and sediment sources in Madagascar inferred from 10Be analysis of lavaka, slope, Journal of Geology, v.117, p. 363-376. 2010, Shakedown in Madagascar, Occurrence of lavakas associated with seismic activity,2012, Relation Between Bedrock Geology, Topography and Lavaka Distribution in Madagascar. South African Journal of Geology 115.2, 225-250, raveloson, A. Visnovitz, F. Székely, B. 2012, A multidisciplinary study on lavaka formation in Central Highlands, raveloson, A. Visnovitz, F. Szabó, Cs. 2012, Sedimentological features of lateritic and saprolitic horizons in a mid-slope lavaka, Central Highlands, european Geoscience Union General Assembly April 22-27, Geophysical Research Abstracts, v.14, EGU2012-4365 Voarintsoa, N. R. Cox, R. Madison, R. M. O, Rakotondrazafy,2012, Lithologic controls on lavaka occurrence in Madagascar. South African Journal of Geology, v.115, p. 225-250,1991, Patterns of development of lavaka, Madagascars unusual gullies, Earth Surface Processes and Landforms, v.16, p. 189-206. 1993, The initiation and growth of gullies in Madagascar, are humans to blame, more about lavakas Lavaka image database at Williams College Digital Collections, Team Lavaka image collection
7.
U-shaped valley
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A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs and they also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia also have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue. The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
8.
Valley network
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Valley networks are branching networks of valleys on Mars that superficially resemble terrestrial river drainage basins. They are found mainly incised into the terrain of the southern highlands. The individual valleys are less than 5 kilometers wide, though they may extend for up to hundreds or even thousands of kilometers across the martian surface. Some authors have argued that the properties of the demand that a hydrological cycle must have been active on ancient Mars. The valleys of the networks are typically narrow and 50–200 m deep and their cross-sectional form tends to evolve from V-shaped in the headwaters to U-shaped in the lower reaches. The individual valleys form interconnected branching networks, typically less than 200 km long and draining into local topographic lows, the form of the tributary valleys is commonly described as stubby or a similar term, implying short lengths away from the trunk streams and amphitheater-like terminations at their heads. Any branched valley system on a smaller than an outflow channel can be termed a valley network. Some valley networks run for over 2000 km across the martian landscape, some have drainage densities which do match some terrestrial values. Narrower, less deep valley networks are present, but probably are more rare than their larger equivalents, in most valley networks, later aeolian processes have deposited wind-blown sediments in the bottoms of the valleys, obscuring the nature of the channel which must have cut them. On Earth, a valley is a depression with a floor, across which migrates a channel. Due to the deposits on Mars, however, in almost all cases it is unclear whether the valley floors contain individual channel structures or whether they are fully inundated in flow events. Nanedi Valles is an example where a channel has been identified. This accounts for the preference in the literature for the term valley network rather than channel network, valley networks are very strongly concentrated in the cratered southern uplands of Mars. The Hesperian-age lava plains of the northern hemisphere are in general almost entirely undissected, however, there are significant numbers of exceptions to this generalization - in particular, many of the Hesperian and younger volcanoes carry networks, as well as several other areas. These valleys also appear qualitatively fresher and less degraded than those in the highlands, however, at finer scales than this the distribution of the valleys where present is highly patchy and discontinuous. Within the highlands, it is not unusual to find heavily dissected slopes immediately adjacent to almost entirely unmodified surfaces and they are also much more prominent on steeper slopes, for example on crater rims, but again may only be present on one side of such a rim. However, the channels on Hesperian surfaces unambiguously demonstrate that valley-forming processes did continue at least in some locations at least some of the time after the Noachian, some crater counting evidence even suggests some highland networks may have formed in the Amazonian. Mechanisms and implied environments for the formation of the valleys remain contentious, beyond this, there are several different scenarios that have been advanced to account for the form and distribution in both space and time of the valleys
9.
Noachis Terra
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Noachis Terra is an extensive southern landmass of the planet Mars. It lies west of the giant Hellas impact basin, roughly between the latitudes −20° and −80° and longitudes 30° west and 30° east, centered on 45°S 350°E and it is in the Noachis quadrangle. The term Noachian epoch is derived from this region, the Planetary Report,34,1, 8-14 Lorenz, R. J. Zimbelman. Dune Worlds, How Windblown Sand Shapes Planetary Landscapes, springer Praxis Books / Geophysical Sciences. ESA Science and Technology, Noachis Terra
10.
Sandstone
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Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
11.
Limestone
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Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
12.
Siltstone
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Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones. Siltstone is a sedimentary rock. As its name implies, it is composed of silt sized particles. Siltstones differ significantly from sandstones due to their smaller pores and higher propensity for containing a significant clay fraction, although often mistaken as a shale, siltstone lacks the fissility and laminations which are typical of shale. Unless the siltstone is fairly shaly, stratification is likely to be obscure, mudstone or shale are rocks that contain mud, which is material that has a range of silt and clay. Siltstone is differentiated by having a majority silt, not clay, folk, R. L.1965, Petrology of sedimentary rocks PDF version. 2nd ed.1981, ISBN 0-914696-14-9 Williams, Howel, Francis J. Turner and Charles M. Gilbert,1954, Petrography, W. H. Freeman
13.
Shale
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Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable, shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. Mudstones, on the hand, are similar in composition. Before the mid 19th century, the slate, shale. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. Non-fissile rocks of similar composition but made of smaller than 0.06 mm are described as mudstones or claystone. Rocks with similar sizes but with less clay and therefore grittier are siltstones. Shale is the most common sedimentary rock, shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock, black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal, red, brown and green colors are indicative of ferric oxide, iron hydroxide, or micaceous minerals. Clays are the constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite, clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and these released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor minerals found in shales and other mudrocks. Shales and mudrocks contain roughly 95 percent of the matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale, black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron and sulfur. Pyrite and amorphous iron sulfide along with carbon produce the black coloration, the process in the rock cycle which forms shale is called compaction. The fine particles that compose shale can remain suspended in long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are found in lakes and lagoonal deposits, in river deltas, on floodplains
14.
Colorado Plateau
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The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico, southern and eastern Utah, and northern Arizona. About 90% of the area is drained by the Colorado River and its tributaries, the Green, San Juan. Most of the remainder of the plateau is drained by the Rio Grande, the Colorado Plateau is largely made up of high desert, with scattered areas of forests. In the southwest corner of the Colorado Plateau lies the Grand Canyon of the Colorado River, much of the Plateaus landscape is related, in both appearance and geologic history, to the Grand Canyon. The nickname Red Rock Country suggests the brightly colored rock left bare to the view by dryness, domes, hoodoos, fins, reefs, river narrows, natural bridges, and slot canyons are only some of the additional features typical of the Plateau. The Colorado Plateau has the greatest concentration of U. S. National Park Service units in the country outside of the Washington, DC metropolitan area. Among its ten National Parks are Grand Canyon, Glen Canyon, Zion, Bryce Canyon, Capitol Reef, Canyonlands, Arches, Mesa Verde, and Petrified Forest. The province is bounded by the Rocky Mountains in Colorado, and by the Uinta Mountains and Wasatch Mountains branches of the Rockies in northern and it is also bounded by the Rio Grande Rift, Mogollon Rim and the Basin and Range Province. Isolated ranges of the Southern Rocky Mountains such as the San Juan Mountains in Colorado, north-south trending normal faults that include the Hurricane, Sevier, Grand Wash, and Paunsaugunt separate the sections component plateaus. This fault pattern is caused by the forces pulling apart the adjacent Basin and Range province to the west. Occupying the southeast corner of the Colorado Plateau is the Datil Section, thick sequences of mid-Tertiary to late-Cenozoic-aged lava covers this section. Development of the province has in part been influenced by structural features in its oldest rocks. Part of the Wasatch Line and its various faults form the edge of the province. Faults that run parallel to the Wasatch Fault that lies along the Wasatch Range form the boundaries between the plateaus in the High Plateaus Section, the Uinta Basin, Uncompahgre Uplift, and the Paradox Basin were also created by movement along structural weaknesses in the regions oldest rock. Some sources also include the Tushar Mountain Plateau as part of the Colorado Plateau, the mostly flat-lying sedimentary rock units that make up these plateaus are found in component plateaus that are between 1500 m to over 3350 m above sea level. A supersequence of these rocks is exposed in the various cliffs, within these rocks are abundant mineral resources that include uranium, coal, petroleum, and natural gas. Study of the unusually clear geologic history has greatly advanced that science. A rain shadow from the Sierra Nevada far to the west, higher areas receive more precipitation and are covered in forests of pine, fir, and spruce
15.
Colorado River
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The Colorado River is one of the principal rivers of the Southwestern United States and northern Mexico. The 1, 450-mile-long Colorado River drains an expansive, arid watershed that encompasses parts of seven U. S. starting in the central Rocky Mountains in the U. S. After entering Mexico, the Colorado approaches the mostly dry Colorado River Delta at the tip of the Gulf of California between Baja California and Sonora. Known for its dramatic canyons, whitewater rapids, and eleven U. S. National Parks, the Colorados large flow and steep gradient are used for generating hydroelectric power, and its major dams regulate peaking power demands in much of the Intermountain West. Intensive water consumption has dried up the lower 100 miles of the river, beginning with small bands of nomadic hunter-gatherers, Native Americans have inhabited the Colorado River basin for at least 8,000 years. Most native peoples that inhabit the basin today are descended from groups that settled in the region beginning about 1,000 years ago. Europeans first entered the Colorado Basin in the 16th century, when explorers from Spain began mapping and claiming the area, early contact between Europeans and Native Americans was generally limited to the fur trade in the headwaters and sporadic trade interactions along the lower river. After most of the Colorado River basin became part of the U. S. in 1846, several expeditions charted the Colorado in the mid-19th century – one of which, led by John Wesley Powell, was the first to run the rapids of the Grand Canyon. American explorers collected valuable information that would later be used to develop the river for navigation, lesser numbers settled in the upper basin, which was the scene of major gold strikes in the 1860s and 1870s. Large engineering works began around the start of the 20th century, with guidelines established in a series of international. The U. S. federal government was the driving force behind the construction of dams and aqueducts in the river system, although many state. Most of the dams in the river basin were built between 1910 and 1970, the system keystone, Hoover Dam, was completed in 1935. The Colorado is now considered among the most controlled and litigated rivers in the world, as demands for Colorado River water continue to rise, the level of human development and control of the river continues to generate controversy. The Colorado begins at La Poudre Pass in the Southern Rocky Mountains of Colorado, after a short run south, the river turns west below Grand Lake, the largest natural lake in the state. As it flows southwest, it gains strength from many tributaries, as well as larger ones including the Blue, Eagle. In a few areas, such as the marshy Kawuneeche Valley near the headwaters, arcing northwest, the Colorado begins to cut across the eponymous Colorado Plateau, a vast area of high desert centered at the Four Corners of the southwestern United States. In Utah, the Colorado flows primarily through the slickrock country and this is one of the most inaccessible regions of the continental United States. Here, the San Juan River, carrying runoff from the slope of Colorados San Juan Mountains, joins the Colorado from the east. S
16.
Mars
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Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is referred to as the Red Planet because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet, Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan, there are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers, liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is about 6⁄1000 that of the Earths, except at the lowest elevations for short periods. The two polar ice caps appear to be largely of water. The volume of ice in the south polar ice cap, if melted. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, optical ground-based telescopes are typically limited to resolving features about 300 kilometers across when Earth and Mars are closest because of Earths atmosphere. Mars is approximately half the diameter of Earth with an area only slightly less than the total area of Earths dry land. Mars is less dense than Earth, having about 15% of Earths volume and 11% of Earths mass, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. It can look like butterscotch, other common colors include golden, brown, tan. Like Earth, Mars has differentiated into a metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ±65 kilometers, consisting primarily of iron and this iron sulfide core is thought to be twice as rich in lighter elements than Earths. The core is surrounded by a mantle that formed many of the tectonic and volcanic features on the planet
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Canyonlands National Park
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Canyonlands National Park is a U. S. National Park located in southeastern Utah near the town of Moab. It preserves a colorful landscape eroded into countless canyons, mesas, and buttes by the Colorado River, the Green River, legislation creating the park was signed into law by President Lyndon Johnson on September 12,1964. The park is divided into four districts, the Island in the Sky, the Needles, the Maze, while these areas share a primitive desert atmosphere, each retains its own character. Author Edward Abbey, a frequent visitor, described the Canyonlands as the most weird, wonderful, Canyonlands is a popular recreational destination. Since 2007, more than 400,000 people have visited the park each year with a record of 776,218 visitors in 2016, the geography of the park is well suited to a number of different recreational uses. Hikers, mountain bikers, backpackers, and four-wheelers all enjoy traveling the rugged, the White Rim Road traverses the White Rim Sandstone level of the park between the rivers and the Island in the Sky. Since 2015, day-use permits must be obtained before travelling on the White Rim Road due to the popularity of driving and bicycling along it. The park services intent is to provide a wilderness experience for all visitors while minimizing impacts on the natural surroundings. Rafters and kayakers float the calm stretches of the Green River, below the Confluence, Cataract Canyon contains powerful whitewater rapids, similar to those found in the Grand Canyon. However, since there is no large impoundment on the Colorado River above Canyonlands National Park, river flow through the Confluence is determined by snowmelt, not management. As a result, and in combination with Cataract Canyons unique graben geology, as of 2016, the Island in the Sky district, with its proximity to the Moab, Utah area, attracts 76.7 percent of total park visitors. The Needles district is the second most visited, drawing 20.7 percent of visitors, the remote Maze district accounts for only about 1.5 percent of visitors, while river rafters and other river users account for the remaining 1.1 percent of total park visitation. Political compromise at the time of the parks creation limited the area to an arbitrary portion of the Canyonlands basin. Conservationists hope to complete the park by bringing the boundaries up to the high sandstone rims that form the border of the Canyonlands landscape. The Colorado River and Green River combine within the park dividing it into three districts called the Island in the Sky, the Needles and the Maze, the Colorado River flows through Cataract Canyon below its confluence with the Green River. The area was home of the Ancestral Puebloans, of which many traces can be found. Although the items and tools used have been largely taken away by looters, some of their stone. The Ancestral Puebloans also left traces in the form of petroglyphs, the Maze district is located west of the Colorado and Green rivers, and is the least accessible section of the park, and one of the most remote and inaccessible areas of the United States
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Utah
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Utah is a state in the western United States. It became the 45th state admitted to the U. S. on January 4,1896, Utah is the 13th-largest by area, 31st-most-populous, and 10th-least-densely populated of the 50 United States. Utah has a population of more than 3 million, approximately 80% of whom live along the Wasatch Front, Utah is bordered by Colorado to the east, Wyoming to the northeast, Idaho to the north, Arizona to the south, and Nevada to the west. It also touches a corner of New Mexico in the southeast, approximately 62% of Utahns are reported to be members of The Church of Jesus Christ of Latter-day Saints or LDS, which greatly influences Utahn culture and daily life. The LDS Churchs world headquarters is located in Salt Lake City, Utah is the only state with a majority population belonging to a single church. The state is a center of transportation, education, information technology and research, government services, mining, in 2013, the U. S. Census Bureau estimated that Utah had the second fastest-growing population of any state. St. George was the metropolitan area in the United States from 2000 to 2005. Utah also has the 14th highest median income and the least income inequality of any U. S. state. A2012 Gallup national survey found Utah overall to be the best state to live in based on 13 forward-looking measurements including various economic, lifestyle, the name Utah is derived from the name of the Ute tribe. It means people of the mountains in the Ute language, according to other sources Utah is derived from the Apache name Yudah which means Tall. These Native American tribes are subgroups of the Ute-Aztec Native American ethnicity and were sedentary, the Ancestral Pueblo people built their homes through excavations in mountains, and the Fremont people built houses of straw before disappearing from the region around the 15th century. Another group of Native Americans, the Navajo, settled in the region around the 18th century, in the mid-18th century, other Uto-Aztecan tribes, including the Goshute, the Paiute, the Shoshone, and the Ute people, also settled in the region. These five groups were present when the first European explorers arrived, the southern Utah region was explored by the Spanish in 1540, led by Francisco Vásquez de Coronado, while looking for the legendary Cíbola. A group led by two Catholic priests—sometimes called the Dominguez-Escalante Expedition—left Santa Fe in 1776, hoping to find a route to the coast of California, the expedition traveled as far north as Utah Lake and encountered the native residents. The Spanish made further explorations in the region, but were not interested in colonizing the area because of its desert nature, in 1821, the year Mexico achieved its independence from Spain, the region became known as part of its territory of Alta California. European trappers and fur traders explored some areas of Utah in the early 19th century from Canada, the city of Provo, Utah was named for one, Étienne Provost, who visited the area in 1825. The city of Ogden, Utah was named after Peter Skene Ogden, in late 1824, Jim Bridger became the first known English-speaking person to sight the Great Salt Lake. Due to the salinity of its waters, Bridger thought he had found the Pacific Ocean
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Green River (Colorado River tributary)
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The Green River, located in the western United States, is the chief tributary of the Colorado River. The watershed of the river, known as the Green River Basin, covers parts of Wyoming, Utah, and Colorado. The Green River is 730 miles long, beginning in the Wind River Mountains of Wyoming and flowing through Wyoming and Utah for most of its course, much of the route is through the Colorado Plateau and through some of the most spectacular canyons in the United States. It is only smaller than the Colorado when the two rivers merge, but typically carries a larger load of silt. The average yearly mean flow of the river at Green River, the status of the Green River as a tributary of the Colorado River came about for mainly political reasons. In earlier nomenclature, the Colorado River began at its confluence with the Green River, above the confluence the Colorado was called the Grand River. Representative Edward T. Taylor petitioned the Congressional Committee on Interstate and it rises in western Wyoming, in northern Sublette County, on the western side of the Continental Divide in the Bridger-Teton National Forest in the Wind River Range. It flows south through Sublette County and western Wyoming in a known as the Upper Green River Valley. At the town of La Barge, it flows into Fontenelle Reservoir, prior to the creation of the reservoir, the Blacks Fork joined the Green River south of Green River, today the mouth of Blacks Fork is submerged by the reservoir. It turns westward back into Utah along the edge of the Uintas in Whirlpool Canyon. In Utah it meanders southwest across the Yampa Plateau and through the Uintah and Ouray Indian Reservation, two miles south of Ouray, Utah, it is joined by Duchesne River, and three miles downstream by the White River. Ten miles farther downstream it is joined by the Willow River, south of the plateau, it is joined by Nine Mile Creek, then enters the Roan Cliffs where it flows south through the back-to-back Desolation and Gray Canyons, with a combined length of 120 mi. In Gray Canyon, it is joined by the Price River, south of the canyon it passes the town of Green River, Utah and is joined by the San Rafael River in southern Emery County. In eastern Wayne County it meanders through Canyonlands National Park where it joins the Colorado, the Flaming Gorge Dam in Utah is a significant regional source of water for irrigation and mining, as well as for hydroelectric power. Begun in the 1950s and finished in 1963, it was highly controversial, originally, a dam was to be built in Whirlpool Canyon, but the conservationist movement traded the Flaming Gorge dam for halting that proposal. Apocryphally, the Sierra Club, an environmental organization, lost its tax-exempt status for political action in opposing the proposed dam. The Green is a large, deep, powerful river and it ranges from 100 to 300 feet wide in the upper course to 300 to 1,500 feet wide in its lower course and ranges from 3 to 50 feet in depth. It is navigable by small craft throughout its course and by large motorboats upstream to Flaming Gorge Dam, near the areas where the Oregon Trail crosses, the river is 400 -500 feet wide and averages about 20 feet deep at normal flow
20.
Headward erosion
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Headward erosion is erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen. When sheets of water on a planar surface first enter a depression in it. Widening of the canyon by erosion inside the canyon, below the side top edge, or origin or the stream. Headward erosion is a process of erosion that lengthens a stream. The stream erodes away at the rock and soil at its headwaters in the direction that it flows. Once a stream has begun to cut back, the erosion is sped up by the gradient the water is flowing down. As water erodes a path from its headwaters to its mouth at a body of water. This leads to increased erosion at the steepest parts, which is headward erosion, if headward erosion continues long enough, it can cause a stream to break through into a neighboring watershed and capture drainage that previously flowed to another stream. For example, headward erosion by the Shenandoah River in the U. S, as each capture added to the Shenandoahs discharge, it accelerated the process of headward erosion until the Shenandoah captured all drainage to the Potomac west of the Blue Ridge Mountains. The water collects in channels where the velocity and erosional power increase, cutting into, subsequent streams form by selective headward erosion by cutting away at less resistive rocks in the terrain. Obsequent and resequent streams form after time in an area of insequent or subsequent streams, obsequent streams are insequent streams that now flow in an opposite direction of the original drainage pattern. Resequent streams are subsequent streams that have changed direction from their original drainage patterns. Headward erosion creates three kinds of drainage patterns, dendritic patterns, trellis patterns, and rectangular and angular patterns. Dendritic patterns form in homogenous landforms where the bedrock has no structural control over where the water flows. They have a characteristic pattern of branching at acute angles with no common or similarly repeating pattern. Trellis patterns form in where the bedrock where there is repeating weaker and stronger types of rock. The trellis pattern cuts down deeper into the bedrock, and is characterized by nearly parallel streams that branch at higher angles. Rectangular and angular patterns are characterized by branching of tributaries at nearly right angles and tributaries which themselves exhibit right-angle bends in their channels and these usually form in jointed igneous bedrocks, horizontal sedimentary beds with well-developed jointing or intersecting faults
21.
PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
