what geologic processes create unconformities?
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An unconformity is a break or a gap in the geologic record. It represents a break in time in the depositional process and can include a period of significant erosion.\n\nThe primary processes that create unconformities in sedimentary rock are eustacy and tectonics. That is sea level change and movement of the earth’s plates. As sea level falls it can expose deposits such as carbonate platforms which will begin to erode and form a karst surface. As sea level rises over this cave and karst system, it will be buried and become what is known as paleokarst. In clastic depositional systems sea level fall will cause rivers to cut downward into their own deposits and delta systems, creating what is called an incised valley. As sea level rises again these incised valleys will be filled again by the same rivers. The base of the new deposits represents the unconformity. \n\nPlate tectonics can also be responsible for lifting areas above sea level. In fact, the two processes of eustacy (sea level) and tectonics are very difficult to separate by examining the rock record. As plates rise, rivers will cut incised valleys, and carbonate platforms will be exposed. Likewise, as plate tectonics cause plates to sink the same systems will be affected and deposition will resume over the new unconformity. \n\nIn aeolian systems climate changes can cause unconformities. As a climate changes from a dry desert to a wetter type of environment, plants can take hold and bring an end to aeolian system. Eventually this may develop into a soil surface and be drowned by sea level changes, beginning a new episode of deposition over the unconformity. All paleosols (ancient soils) represent an unconformity.  \n\nIn volcanic terranes the unconformities are created by the gaps in time between eruption events. These can be short, or millions of years long. \n\nIn a metamorphic terrane an unconformity often is found between eroded metamorphics and sedimentary rocks.
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Convergent boundaries occur where two plates are being pushed together and collide. This is sometimes called a "destructive plate margin". One thing to keep in mind is that when subduction occurs, the denser plate (usually the older one) generally is considered to be the one that is pushed into the hot asthenosphere. Its rocks are melted and the resulting hot magma migrate upward along cracks and weakened areas in the overriding plate forming volcanoes. Of course, you always get earthquakes along with this process. The regions where the earthquakes occur are called the Wadati-Benioff zones. However, what actually happens depend on the composition of the crustal plates involved.\n\nOceanic colliding with continental crustal plates: An example of this is the subduction of the denser oceanic Nazca Plate under the South American Plate, pushing limestone strata upward to form the towering Andes and generating destructive earthquakes. Another example is the Cascadian subduction zone off the northwest coast of the U.S. you can find volcanoes along the subduction zones. Deep trenches are formed as a result of subduction.
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Error and Deposition by Gravity\n\nGravity is the force of attraction that exists between all objects. Because Earth has great mass, other objects are attracted to Earth. This makes gravity a force of erosion and deposition. Gravity causes loose materials to move down a slope. When gravity alone causes materials to move downslope, this type of erosion is called mass movement. \n\nA slump is a mass movement that happens when loose materials of rock layers slip down a slope. In a slump, strong rock or sediment lies over weaker materials. \n\nCreep gets its name from the way sediments slowly inch their way down a hill. \n\n"Falling Rock" sign warn of another type of mass movement called a rockslide. Rockslides happen when large blocks of rock break loose from a steep slope and start tumbling. As they fall, these rocks crash into other rocks and knock them loose. \n\nMudflows usually occur in relatively dry areas where weathering accumulates thick layers of dry sediments. When heavy rains fall in these areas, water mixes with sediments and forms a thick pasty substance. Gravity causes this mass to slide downhill\n\nGlaciers\n\nGlaciers are agents of erosion. When snow doesn’t melt, it begins piling up. The weight of the snow becomes great enough to compress its bottom layers into ice. The ice on the bottom partially melts and becomes putty-like. The whole mass begins to slide on this putty-like layer, and it moves downhill. \n\nContinental glaciers are huge masses of ice and when snow  once covered up to 28 percent of Earth they were called ice ages. Today glaciers cover only 10 percent of Earth, mostly near the poles in Antarctica and Greenland. \n\nValley glaciers occur even in high mountains where the average temperature is low enough to prevent snow from melting during the summer. \n\nGlacial Erosion\n\nAs they move over land, glaciers are like bulldozers, pushing loose materials out of their path. Eroded sediments get pushed in front of a glacier, carried underneath it and piled up along its sides. When glacial ice melts, water flows into cracks in rock, refreezes in these cracks, expands and fractures the rock into pieces. These rock pieces are then lifted out by the glacial ice sheet. This process, called plucking, results in boulders, gravel and sand being added to the bottom and sides of a glacier. As a glacier movers forward, plucked rock fragments and sand at its base scrape the soil and bedrock, eroding even more material than ice alone could. When bedrock is gouged deeply by dragged rock fragments, these marks called grooves, are deep, long, parallel scars on rock. Less-deep marks are called striations.\n\nGlacial Depostion\n\nWhen glaciers begin to melt, they no longer have enough energy to carry much sediment. The sediment drops or is deposited on the land. This mixture of different sized sediments is called till. When melting of a glacier exceeds snow accumulation, the glacier retreats or starts to melt. Material deposited by the melting water from a glacier is called outwash.\n\nWind\n\nWind erosion occurs when wind picks up loose material and transports it to other places. Wind erodes Earth’s surface by deflation and abrasion. When wind erodes by deflation, it blows across loose sediment, removing small particles such as clay, silt, and sand, leaving coarse material behind. When these windblown sediments strike rock, they erode by abrasion.\n\nSand storms occur when wind-blown sand grains form a low cloud, just above the ground. Dust storms occur when wind carried dry soil over hundreds of miles. \n\nTo reduce wind erosion, windbreaks are planted to catch blowing soil. Along many steep slopes, seacoasts and deserts, people plant vegetation to hold the soil with plant roots. Sediments blow by soil eventually deposited and develop into either a loess or a dune. Fine-grained sediments of soil deposited on hilltops and in valleys are loess. Sand mounded in front of an obstacle, such as a rock, produces
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well I don't know how old it is but I'm pretty sure they formed from two tectonics plates crashing in a convergent matter causing reverse faults\n\nin other words two land plate crashed and all that pressure made the mountains
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1. Continental drift or plate tectonics.\n\n2. Horizontal fault line.
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I was told that it was becuase of the mountains.The ice or snow of mountains would melt into water,forming small rivers that turn into more and more bigger rivers{or something like that} that turn into oceans."Where does the snow of a mountain or ice of a mountain come from?",you might ask.That I dont know.
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"Created" does not acurately describe geologic formations, as creation implies a start and a finish; geologic processes have no end point. Dating of the sediments that make up the Grand Canyon show an age range of about 2000 million years evident by the Vishnu Shist in the very depths of the gorge, to the 230 million year old limestone near the upper rim. No, it is most definitely not the same as it has always been, as this "creation" process has occured over thousands of millions of years, constantly changing and reshaping the canyon via weathering.
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I'm not going to write this in 6 sentences for you but...\n\nIgneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either the Earth's mantle or crust. Typically, the melting is caused by one or more of the following processes -- an increase in temperature, a decrease in pressure, or a change in composition.
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Sedimentary rock forms relatively flat. Youngest always on top of the oldest. Just like a stack of newspapers if you were to accumulate them everyday.\n\nFolding from compressional stress is one. Rock is literally pushed together creating anticlines & synclines, upward folding & downward folding arches respectively.\n\nFaults can also do this. This can be accomplished through compressional (pushed together) or tensional (pulled apart) stresses.\n\nI am not too sure about this one but isostatic adjustment could possibly tilt rocks.\n\nHope this helps.\n\n:)
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Erosion breaks up igneous and metamorphic rocks, and the particles build up to create sedimentary rocks.  \n\nHope this is helpful.
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My guess is dissipation, hydrothermal, volcanic. Just guessing.
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I think you mean rock fragments. If yes,\n\nRock fragments are further eroded by forces of nature: wind or water. depending on the level of disintegration, it forms various kinds of soil or sand.\n\nSometimes if fragments get buried under several layers of soil, fragments clump together to form sedimentary rocks\n\nHope that helps\n\nR
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There are a couple ways. Hot spots can build up islands through volcanic activity, like Hawaii. Some islands can be created by subduction volcanism (Japan). Other islands can be uplifted at convergent or possibly transverse plate boundaries.\n\nIslands can also be created by erosion and inundation, as in a case of sea level rise where the water covers low lying areas while higher areas get "separated" from the land by water (St. Lawrence Island in Alaska). Glaciers can scour channels around large land masses, then recede and the channels can become filled with water to surround the land masses and make them islands. Manhattan Island was actually created by a continental glacier pushing a bunch of sediment out into the ocean and then receeding (it is a moraine).\n\nSome islands can be created purely by sediment deposition, such as those at the mouths of deltas.
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I remember reading somewhere that the great New Madrid earthquake in the early 1800s was so powerful that it caused the Mississippi River to flow in the opposite direction for a time.  I imagine that tectonic activity - movement that changes the shape of the earth's crust - would do it.
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You've been given exhaustive lists, copied directly from websites without giving proper citation I imagine. \n\nHere is how to think about this question so that you can recall and understand the answer, without just memorizing a bunch of rock names.\n\nUse the rock cycle. Igneous rocks are of two groups, those formed within the earth and those formed by volcanism.  The volcanic rocks will show signs of that volcanism and will be things like black columnar basalt found in massive flows. Obsidian (volcanic glass) that flowed as liquid, scoria and pumice which are like foam because the dissolved gases expanded and made them bubble as they hardened. The other igneous group formed under the earth's surface, and includes things like granite where you can see the crystals that formed as it cooled and solidified. \n\nSedimentary rocks are also in two major informal groups (and a minor third). The first group of sedimentary rocks is clastics. These are formed by weathering, transport and deposition. Weatherings breaks down rocks like igneous, metamorphic and even sedimentary rocks and transport by wind, water, or gravity deposits these rocks as accumulations of clasts, (thus clastics). They become sandstone, shale, and conglomerate. The other major sedimentary group is carbonates. These rocks are 'born' because they are formed by living things. Ocean environments (and lakes too) have many organisms that make shells, corals that make reefs, and algae that make fine carbonate sediments (known as carbonate mud). Even bacteria get into the act helping to precipitate carbonates in many ocean environments. The third group of sedimentary rocks is those that are dissolved by water and deposited by evaporation or precipitation. These include gypsum, halite, sylvite, and many more. \n\nMetamorphic rocks all start life as one of the previous groups. You can metamorphose a granite into a granitic gneiss by burial, pressure and heat. You can metamorphose a basalt into an amphibolite. You can make limestone into marble. Sandstone turns into quartzite.\n\nRemember the rock cycle, associate the rocks as they move through it, and you won't have trouble remembering examples of rock types. Also don’t get tripped up by the difference between a mineral and a rock. Geologists sometimes use the two terms identically, but there is a formal difference between a rock (which is an impure mixture) and a mineral that is chemically consistent.
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Actually there are many important and major exceptions to the examples already provided here. While it is true that many minerals form either by crystallization from a molten state, or by crystallization from solution, there are several other important methods of mineral formation. \n\nMetamorphism is the solid state change of molecular arrangement that forms many minerals without melting or dissolution. A common group of minerals often formed by metamorphism, which is the result of high (but not high enough to liquify) temperatures and/or high pressures are garnets. Other examples are  muscovite, sillimanite, biotite, kyanite, and many more.\n\nAnother example of a change in mineral composition that does not involve either dissolution or melting is the common change of anhydrite to gypsum by hydration. Anhydrite contains only CaSO4, and when H2O is chemically combined (hydrated) with anhydrite it becomes gypsum. The process can be reversed releasing the water by a change in pressure.  There are a large number of minerals that are found either in a hydrated state (chemically combined with H2O) or in a dehydrated state. Many clay minerals will change composition under pressure and heat without melting or being dissolved in water. \n\nOther minerals that are an important group are what are known as polymorphs. Polymorphs are minerals that share the same chemical composition, but have varied molecular structure. A good example of a polymorph is calcite and aragonite. Aragonite has the same chemical composition of calcite (CaCO3), but is unstable at low temperature and pressure. At a temperature of 400 degrees C, with no change in pressure, aragonite will spontaneously alter to calcite. No melting or dissolution is involved. \n\nHere's a reference for calcite/aragonite:\nhttp://www.galleries.com/minerals/carbonat/aragonit/aragonit.htm\n\nSome minerals (as in rocks) even form by biogenic processes, however the generally accepted definition of a mineral (Nickel, 1995, Canadian Mineralogist) excludes most of these from being true minerals. While these 'biominerals' may involve precipitation of the mineral from solution, the process is not straightforward precipitation as it involves a living organism. One common example is the calcite which is deposited by molluscs as part of their shells (some deposit aragonite) and many other organisms. Many bacteria play an important role in creating some biominerals. Some ore deposits of zinc sulfides are deposited by bacterial activity. See: http://www.sciencenews.org/articles/20031115/bob9.asp\nSome commercially important iron ore deposits such as banded iron formations, were deposited by the activity of cyanobacteria and contain several iron minerals. You could argue that this was simply a precipitate from a solution, but the cyanobacteria played an important role in adding the oxygen to the water that caused the iron to precipitate out. Your teeth are another example of a biogenically deposited "biomineral". Your teeth contain hydroxy apatite. Another interesting example is the biomineral equivalent of atacamite that is found in the teeth of bloodworms. This copper mineral is quite rare and the type locality for the non-biogenically formed mineral is the driest desert in the world, the Atacama of northern Chile.\nhttp://webmineral.com/data/Atacamite.shtml \nHere is the article about the bloodworm teeth:\nhttp://www.sciencenews.org/articles/20021109/note14.asp\n\nTwo other minerals that have an interesting method of formation are coesite and stishovite. These are rare dense forms of SiO2 (polymorphs of quartz) that are only found in meteorite impact craters and rarely in the kimberlite pipes where diamonds are found. These two polymorphs of quartz are formed under about 20 kilobars of pressure or more during a meteorite impact. It is hard to say if they undergo a molten state, but because they are metastable, it seems unlikely to me that they would have formed and retaine
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Minerals are what make up rocks.  When Earth's rocks erode, these minerals are released.  A lot of times, erosion takes place in higher elevation areas because the denudation (erosion) rate of higher elevations is also higher than lower elevations and streams usually stem from places of higher elevation.  Minerals then are deposited into these streams.