:: wikimiki.org ::
| Bedrock |
Bedrock:This article is about the type of rock. Bedrock is also the name of the town in which The Flintstones lived.
Bedrock is the native consolidated rock underlying the Earth's surface. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil. The term implies that the rock lies in beds, or strata. Under any given location on the surface of the planet, rock will be found.
The term bedrock may be somewhat misleading, since in many locations, the bedrock may change over a short distance, or the technical bedrock may be a thin stratum overlying quite different rock.
A geologic map of an area will usually show bands of differing rock type exposure, i.e. rock that would be exposed at the surface if all soil were removed. The different rock strata or layers that are indicated may be a result of either nonparallel (sloping) surface erosion at the edges of flat strata or normal surface erosion of tilted strata that has removed the upper portions of higher layers.
See also
- geology
- igneous rock
- metamorphic rock
- rock (geology)
- sedimentary rock
- stratigraphy
- topography
Category:Geology
Bedrock (The Flintstones):For the type of rock, see bedrock.
Bedrock is the fictional prehistoric city that is home to the characters of the television animated series The Flintstones.
Size
Though the opening credits of the original Flintstones series showed the town's population as only 2,500, Bedrock was generally presented as a medium-sized American city, with all the amenities of such, but with a "prehistoric" twist. For instance, dinosaurs were seen being used as cranes at the town's most well-known employer, "Slate Rock and Gravel" (also known as "Rockhead and Quarry Cave Construction Company" in the series' earlier episodes).
Features
The climate of Bedrock was somewhat undetermined, since different Flintstones episodes and media have portrayed it differently. Palm trees and cycads were common yard trees, suggesting a warm climate. However, episodes and movies set at Christmastime depicted plenty of snow. Sometimes the wilderness on Bedrock's outskirts appeared to be desert-like, whereas other times it resembled a tropical/subtropical jungle.
In terms of educational features, Bedrock apparently had just one high school, Bedrock High School, alma mater of Fred Flintstone, and later his daughter Pebbles. Near Bedrock could also be found "Prinstone University" (a parody of Princeton University).
For a town its size, Bedrock has a sizeable concentration of media. Bedrock had at least one radio station (which had the call letters "BDRX") several television stations, and several newspapers. One of the newspapers was The Daily Granite, edited by Lou Granite, that for a time employed Wilma Flintstone and Betty Rubble as reporters. Another was The Daily Slab. Television programs produced in Bedrock included the cooking program The Happy Housewife Show and the teen dance program Shinrock (a parody of 1960s television program Shindig). Other favorite programs of Bedrock citizens, though not produced there, included such fare as Peek-a-Boo Camera (a parody of Candid Camera) and variety program The Ed Sulleystone Show (a parody of The Ed Sullivan Show).
In terms of entertainment, Bedrock featured a drive-in movie theater where films such as The Monster would play, the amphitheater The Bedrock Bowl, and several nightclubs.
There were plenty of dining options in Bedrock as well, including a drive-in restaurant serving Brontosaurus ribs.
Regarding health care, Bedrock had the Rockapedic Hospital, where Pebbles was born.
Other businesses included bowling alleys, pool halls, health clubs, one catering service (as the owner proclaimed, "we're the only caterer in town!"), and the Pyrite Advertising Agency, where Pebbles worked as an adult.
Not much is known of the layout of Bedrock, but it does include Cobblestone Way, the street the Flintstones and the Rubbles live (though the original series also listed it as Cobblestone Lane and as Stonecave Road).
The people of Bedrock tended to be fairly friendly, if not without having various quirks. The denizens of Bedrock had a strong sense of civic spirit, and tended to participate in various charities, parades, and so forth.
Location
Bedrock was located in fictional Cobblestone County; presumably, the nearby town of Red Rock was located in Cobblestone County as well. However, no further location was ever given for any of these locations, besides being set in a prehistoric version of the United States. Bedrock was in one episode shown as being a two day drive from "Rock Vegas" (a parody of Las Vegas, Nevada) and, in another episode, several hours' drive from "Indiarockolis" (a parody of Indianapolis, Indiana). Travel to "Hollyrock," a parody of Hollywood, California, usually involved an "airplane" flight --- the "plane" in this case often shown as a giant pterodactyl.
External links
- [http://www.topthat.net/webrock/index.htm Webrock - The Flintstones and Hanna Barbera Page]
Category: The Flintstones
Category: Fictional towns and cities
SubsoilÓģ Ķ ķ Ļ ļ Ņ ņ Ŗ ŗ Ş ş Ţ ţ Ć ć Ĺ ĺ Ń ń Ŕ ŕ Ś ś Ý ý Ź ź Đ đ Ů ů Č č Ď ď Ľ ľ Ň ň Ř ř Š š Ť ť Ž ž Ǎ ǎ Ě ě Ǐ ǐ Ǒ ǒ Ǔ ǔ Ā ā Ē ē Ī ī Ō ō Ū ū ǖ ǘ ǚ ǜ Ĉ ĉ Ĝ ĝ Ĥ ĥ Ĵ ĵ Ŝ ŝ Ŵ ŵ Ŷ ŷ Ă ă Ğ ğ Ŭ ŭ Ċ ċ Ė ė Ġ ġ İ ı Ż ż Ą ą Ę ę Į į Ų ų Ł ł Ő ő Ű ű Ŀ ŀ Ħ ħ Ð ð Þ þ Œ œ Æ æ Ø ø Å å Ə ə – — … [] ~ | ° § → ≈ ± − × ¹ ² ³ ‘ “ ’ ” £ € Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω
Geologic mapA geologic map is a special-purpose map made for the purpose of showing subsurface geological features. In the United States, geologic maps are usually superimposed over a topographic map (and at times over other base maps) with the addition of a color mask with letter symbols to represent the kind of geologic unit, stratigraphic contour lines, fault lines, strike and dip symbols, and various additional symbols as indicated by the map key.
The color mask denotes the exposure of the immediate bedrock, even if obscured by soil or other cover. Each area of color denotes a geologic unit or particular rock formation (as more information is gathered new geologic units may be defined). However, in areas where the bedrock is overlain by a significantly thick unconsolidated burden of till, terrace deposits, loess deposits, or other important feature, these are shown instead.
The stratigraphic contour lines are drawn on the surface of a selected deep stratum, so that they can show the topographic trends of the strata under the ground. It is not always possible to properly show this when the strata are extremely fractured, mixed, in some discontinuities, or where they are otherwise disturbed.
Strike and dip symbols consist of (at minimum) a long line, a number, and a short line which are used to indicate tilted beds. The long line is the strike line, which shows the true horizontal direction along the bed, the number is the dip or number of degrees of tilt above horizontal, and the short line is the dip line, which shows the direction of tilt.
Whereas topographic maps are produced by the United States Geological Survey in conjunction with the states, geologic maps are usually produced by the states. There are almost no geologic map resources for some states, while a few states, such as Kentucky, are extensively mapped geologically.
The oldest preserved geologic map is the Turin papyrus, made around 1150 BCE for gold deposits in Egypt.
See also
- Geology
- Geography
- Cartography
External links
- [http://www2.nature.nps.gov/geology/usgsnps/gmap/gmap1.html Geologic Maps] from USGS National Park Service
- [http://ngmdb.usgs.gov/ USGS National Geologic Map Database]
Category:Cartography
Category:Geology
ja:地質図
GeologyGeology (from Greek γη- (ge-, "the earth") and λογος (logos, "word", "reason")) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. It is one of the Earth sciences. Geologists have helped establish the age of the Earth at about 4.5 billion (4.5x109) years, and have determined that the Earth's lithosphere, which includes the crust, is fragmented into tectonic plates that move over a rheic upper mantle (asthenosphere) via processes that are collectively referred to as plate tectonics. Geologists help locate and manage the earth's natural resources, such as petroleum and coal, as well as metals such as iron, copper, and uranium. Additional economic interests include gemstones and many minerals such as asbestos, perlite, mica, phosphates, zeolites, clay, pumice, quartz, and silica, as well as elements such as sulfur, chlorine, and helium.
Astrogeology refers to the application of geologic principles to other bodies of the solar system. However, specialised terms such as selenology (studies of the Moon), areology (of Mars), etc., are also in use.
The word "geology" was first used by Jean-André Deluc in the year 1778 and introduced as a fixed term by Horace-Bénédict de Saussure in the year 1779. An older meaning of the word was first used by Richard de Bury. He used it to distinguish between earthly and theological jurisprudence.
History
In China, the polymath Shen Kua (1031 - 1095) formulated a hypothesis for the process of land formation: based on his observation of fossil shells in a geological stratum in a mountain hundreds of miles from the ocean, he inferred that the land was formed by erosion of the mountains and by deposition of silt.
The work on rocks Peri lithon by Theophrastus, a student of Aristotle, remained authoritative for millennia. However, its interpretation of fossils was not overturned until after the Scientific Revolution. It was translated into Latin and the other languages of Europe such as French. Georg Bauer (Georg Agricola), a physician, summarised the knowledge of mining and metallurgy in 1556.
Georg Agricola (1494-1555) wrote the first systematic treatise about mining and smelting works, De re metallica libri XII, with an appendix Buch von den Lebewesen unter Tage (book of the creatures beneath the earth). He covered subjects like wind energy, hydrodynamic power, melting cookers, transport of ores, extraction of soda, sulfur and alum, and administrative issues. The book was published in 1556.
By the 1700s Jean-Etienne Guettard and Nicolas Desmarest hiked central France and recorded their observations on geological maps; Guettard recorded the first observation of the volcanic origins of this part of France. James Hutton recorded his Theory of the Earth in the 1788 Transactions of the Royal Society of Edinburgh, later called uniformitarianism.
William Smith (1769-1839) drew some of the first geological maps and began the process of ordering rock strata (layers) by examining the fossils contained in them.
James Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained his theory that the Earth must be much older than had previously been supposed in order to allow enough time for mountains to be eroded and for sediment to form new rocks at the bottom of the sea, which in turn were raised up to become dry land.
Followers of Hutton were known as Plutonists because they believed that some rocks were formed by vulcanism which is the deposition of lava from volcanoes, as opposed to the Neptunists, who believed that all rocks had settled out of a large ocean whose level gradually dropped over time.
In 1811 Georges Cuvier and Alexandre Brongniart published their explanation of the antiquity of the Earth, inspired by Cuvier's discovery of fossil elephant bones in Paris. To prove this, they formulated the principle of stratigraphic succession of the layers of the earth. They were independently anticipated by William Smith's stratigraphic studies on England and Scotland.
Sir Charles Lyell first published his famous book, Principles of Geology, in 1830 and continued to publish new revisions until he died in 1875. He successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earth's history and are still occurring today. In contrast, catastrophism is the theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time.
catastrophism illustrated on relief globe of the Field Museum ]]
By 1827 Charles Lyell's Principles of Geology reiterated Hutton's uniformitarianism, which influenced the thought of Charles Darwin.
19th Century geology revolved around the question of the Earth's exact age. Estimates varied from a few 100,000 to billions of years. The most significant advance in 20th century geology has been the development of the theory of plate tectonics in the 1960s. Plate tectonic theory arose out of two separate geological observations: seafloor spreading and continental drift. The theory revolutionised the Earth sciences.
The theory of continental drift was proposed by Alfred Wegener in 1912 and by Arthur Holmes, but wasn't broadly accepted until the 1960s when the theory of plate tectonics was developed.
Important principles of geology
There are a number of important principles in geology. Many of these involve the ability to provide the relative ages of strata or the manner in which they were formed.
The Principle of Intrusive Relationships concerns crosscutting intrusions. In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock. There are a number of different types of intrusions, including stocks, laccoliths, batholiths, sills and dikes.
The Principle of Cross-cutting Relationships pertains to the formation of faults and the age of the sequences through which they cut. Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault. Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault.
The Principle of Inclusions and Components states that, with sedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them. For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer. A similar situation with igneous rocks occurs when xenoliths are found. These foreign bodies are picked up as magma or lava flows, and are incorporated, later to cool in the matrix. As a result, xenoliths are older than the rock which contains them.
The Principle of Uniformitarianism states that, the geologic processes observed in operation that modify the Earth's crust at present have worked in much the same way over geologic time. A fundamental principle of geology advanced by the 18th century Scottish physician and geologist James Hutton, is that "The Present is the Key to the Past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now."
The Principle of Original Horizontality states that, the deposition of sediments occurs as essentially horizontal beds. Observation of modern marine and nonmarine sediments in a wide variety of environments supports this generalisation (although cross-bedding is inclined, the overall orientation of cross-bedded units is horizontal).
The Principle of Superposition states that, a sedimentary rock layer in a tectonically undisturbed sequence is younger than the one beneath it and older than the one above it. Logically a younger layer cannot slip beneath a layer previously deposited. This principle allows sedimentary layers to be viewed as a form of vertical time line, a partial or complete record of the time elapsed from deposition of the lowest layer to deposition of the highest bed.
The Principle of Faunal Succession is based on the appearance of fossils in sedimentary rocks. As organisms exist at the same time period throughout the world, their presence or (sometimes) absence may be used to provide a relative age of the formations in which they are found. Based on principles laid out by William Smith almost a hundred years before the publication of Charles Darwin's theory of evolution, the principles of succession were developed independently of evolutionary thought. The principle becomes quite complex, however, given the uncertainties of fossilisation, the localisation of fossil types due to lateral changes in habitat (facies change in sedimentary strata), and that not all fossils may be found globally at the same time.
Fields or related disciplines
- Earth science
- Economic geology
- Mining geology
- Petroleum geology
- Engineering geology
- Environmental geology
- Geoarchaeology
- Geochemistry
- Biogeochemistry
- Isotope geochemistry
- Geochronology
- Geodetics
- Geomicrobiology
- Geomorphology
- Geophysics
- Glaciology
- Historical geology
- Hydrogeology or geohydrology
- Marine geology
- Mineralogy
- Paleoclimatology
- Paleontology
- Micropaleontology
- Palynology
- Petrology
- Plate tectonics
- Sedimentology
- Seismology
- Soil science
- Pedology (soil study)
- Speleology
- Stratigraphy
- Biostratigraphy
- Structural geology
- Volcanology
Regional geology
- Geology of the Alps
- Geology of the Himalaya
- Geology of Victoria (Australia)
United Kingdom
- Geology of Dorset
- Geology of Hampshire
- Geology of Hertfordshire
United States
- Geology of the Bryce Canyon area(Utah)
- Geology of the Canyonlands area (Utah)
- Geology of the Capitol Reef area (Utah)
- Geology of Connecticut
- Geology of the Death Valley area (California)
- Geology of the Grand Canyon area (Arizona)
- Geology of the Grand Teton area (Wyoming)
- Geology of the Lassen area (California)
- Geology of Mount Shasta (California)
- Geology of the Yosemite area (California)
- Geology of the Zion and Kolob canyons area (Utah)
- Glacial geology of the Genesee River (New York, Pennsylvania)
National geology
- Geology of Australia
- Geology of Victoria
- Geology of Iran
- Geology of India
- Geology of Sikkim
- Geology of the United States of America
- Geology of California
- Geology of the Grand Canyon area
- Geology of the United Kingdom
- Geology of Japan
Planetary geology
- Geology of Mars
- Geology of the Moon
See also
- Timeline of geology
- List of geology topics
- Geologist
- Geologic modeling
- Geologic timescale
- Mineral
- International Union of Geological Sciences (IUGS)
- Important publications in geology
External links
- James Hutton's [http://www.mala.bc.ca/~johnstoi/essays/Hutton.htm Theory of the Earth]
- James Hutton's [http://www.uwmc.uwc.edu/geography/hutton/hutton.htm Theory of the Earth & Abstract of the Theory of the Earth]
Category:Geology
ko:???
ja:???
th:?????????
Metamorphic rockMetamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in form" (from the Greek words meta, "change", and morphe, "form"). The protolith is subjected to extreme heat (greater than 150 degrees Celsius) and pressure causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock.
Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral assembly (metamorphic facies). They are formed deep beneath the Earth's surface by great stresses and high pressures and temperatures. They are also formed by the intrusion of molten rock, called magma, into solid rock and form particularly at the place of contact between the magma and solid rock where the temperatures are high.
The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides us with valuable information about the temperatures and pressures that occur at great depths within the Earth's crust.
Metamorphic Minerals
Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals include kyanite, staurolite, sillimanite, andalusite, and some garnets.
Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals formed during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are stable only within certain limits, and the presence of some minerals in metamorphic rocks indicates the approximate temperatures and pressures at which they were formed.
The change in the particle size of the rock during the process of metamorphism is called recrystallization. For instance, the small calcite crystals in the sedimentary rock limestone change into larger crystals in the metamorphic rock marble, or in metamorphosed sandstone, recrystallisation of the original quartz sand grains results in very compact quartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow the atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact.
Foliation
The layering within metamorphic rocks is called foliation (derived from the Latin word folia, meaning "leaves"), and it occurs when a strong compressive force is applied from one direction to a recrystallizing rock. This causes the platy or elongated crystals of minerals, such as mica and chlorite, to grow with their long axes perpendicular to the direction of the force. This results in a banded, or foliated, rock, with the bands showing the colours of the minerals that formed them.
Textures are separated into foliated and non-foliated categories. Foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage: for example, slate is a foliated metamorphic rock, originating from shale. Non-foliated rock does not have planar patterns of stress.
Rocks that were subjected to uniform pressure from all sides, or those which lack minerals with distinctive growth habits, will not be foliated. Slate is an example of a very fine-grained, foliated metamorphic rock, while phyllite is coarse, schist coarser, and gneiss very coarse-grained. Marble is generally not foliated, which allows its use as a material for sculpture and architecture.
Another important mechanism of metamorphism is that of chemical reactions that occur between minerals without them melting. In the process atoms are exchanged between the minerals, and thus new minerals are formed. Many complex high-temperature reactions may take place, and each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism.
Metasomatism is the drastic change in the bulk chemical composition of a rock that often occurs during the process of metamorphism. It is due to the introduction of chemicals from other surrounding rocks. Water may transport these chemicals rapidly over great distances. Because of the role played by water, metamorphic rocks generally contain many elements that were absent from the original rock, and lack some which were originally present. Still, the introduction of new chemicals is not necessary for recrystallization to occur.
Types of Metamorphism
Contact metamorphism is the name given to the changes that take place when magma is injected into the surrounding solid rock (country rock). The changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact metamorphism aureole. Aureoles may show all degrees of metamorphism from the contact area to unmetamorphosed (unchanged) country rock some distance away. The formation of important ore minerals may occur by the process of metasomatism at or near the contact zone.
Regional metamorphism is the name given to changes in great masses of rock over a wide area, often within orogenic belts. The high temperatures and pressures in the depths of the Earth are the cause of the changes, and if the metamorphosed rocks are uplifted and exposed by erosion, they may occur over vast areas at the surface. The process of metamorphism may have destroyed the original features that could have revealed the rock's previous history. Recrystallization of the rock will destroy the textures and fossils present in sedimentary rocks. Metasomatism will change the original composition.
Metamorphic rock textures
The five basic metamorphic textures with typical rock types are:
- Slaty: slate and phyllite; the foliation is called 'slaty cleavage'
- Schistose: schist; the foliation is called 'schistocity'
- Gneissose: gneiss; the foliation is called 'gneisocity'
- Grandoblastic: granulite, some marbles and quartzite
- Hornfelsic: hornfels and skarn
See also
- List of minerals
- List of rocks
- Blueschist
External links
- [http://www.metu.edu.tr/home/www64/geoweb/Metamorphic.htm Metamorphic textures - Middle East Technical University]
- [http://www.geo.ua.edu/intro03/Meta.html Metamorphism - U. of Alabama]
- [http://www.tulane.edu/~sanelson/geol212/typesmetamorph.htm Types of metamorphism - Tulane U.]
Category:Petrology
Category:Metamorphic rocks
ja:変成岩
th:หินแปร
Sedimentary rock. Cumberland Plateau, Tennessee.]]
Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in three main ways—by the deposition of the weathered remains of other rocks (known as clastic sedimentary rocks); by the deposition of the results of biogenic activity; and by precipitation from solution. Sedimentary rocks include common types such as chalk, limestone, sandstone, and shale.
Formation
Sedimentary rocks are formed from overburden pressure as particles of sediment are deposited out of air, ice, or water flows carrying the particles in suspension. As sediment deposition builds up, the overburden (or lithostatic) pressure squeezes the sediment into layered solids in a process known as lithification ("rock formation") and the original connate fluids are expelled. The term diagenesis is used to describe all the chemical, physical, and biological changes undergone by a sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering).
Sedimentary rocks contain important information about the history of the Earth. They contain fossils, the preserved remains of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remnants.
The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only five percent of the total. As such, the sedimentary sequences we see represent only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.
Classification
Clastic sedimentary rocks
Clastic sedimentary rocks are composed of discrete fragments or clasts of materials derived from other rocks. They are composed largely of quartz with other common minerals including feldspars, amphiboles, clay minerals, and sometimes more exotic igneous and metamorphic minerals.
Clastic sedimentary rocks may be regarded as falling along a scale of grain size, with shale being the finest with particles less than 0.004 mm, siltstone being intermediate with particles between 0.004 to 0.06 mm, and sandstone being coarser still with grains 0.06 to 0.2 mm, and conglomerates and breccias being the coarsest with grains 2 to 256 mm.
The classification of clastic sedimentary rocks is complex because there are many variables involved. Particle size (both the average size and range of sizes of the particles), composition of the particles, the cement, and the matrix (the name given to the smaller particles present in the spaces between larger grains) must all be taken into consideration.
Shales, which consist mostly of clay minerals, are generally further classified on the basis of composition and bedding.
Courser clastic sedimentary rocks are classified according to their particle size and composition. Orthoquartzite is a very pure quartz sandstone; arkose is a sandstone with quartz and abundant feldspar; greywacke is a sandstone with quartz, clay, feldspar, and metamorphic rock fragments present, which was formed from the sediments carried by turbidity currents.
All rocks disintegrate slowly as a result of mechanical weathering and chemical weathering.
Mechanical weathering is the breakdown of rock into particles without producing changes in the chemical composition of the minerals in the rock. Ice is the most important agent of mechanical weathering. Water percolates into cracks and fissures within the rock, freezes, and expands. The force exerted by the expansion is sufficient to widen cracks and break off pieces of rock. Heating and cooling of the rock, and the resulting expansion and contraction, also aids the process. Mechanical weathering contributes further to the breakdown of rock by increasing the surface area exposed to chemical agents.
Chemical weathering is the breakdown of rock by chemical reaction. In this process the minerals within the rock are changed into particles that can be easily carried away. Air and water are both involved in many complex chemical reactions. The minerals in igneous rocks may be unstable under normal atmospheric conditions, those formed at higher temperatures being more readily attacked than those which formed at lower temperatures. Igneous rocks are commonly attacked by water, particularly acid or alkaline solutions, and all of the common igneous rock forming minerals (with the exception of quartz which is very resistant) are changed in this way into clay minerals and chemicals in solution.
Rock particles in the form of clay, silt, sand, and gravel, are transported by the agents of erosion (usually water, and less frequently by ice and wind) to new locations and redeposited in layers, generally at a lower elevation.
These agents reduce the size of the particles, sort them by size, and then deposit them in new locations. The sediments dropped by streams and rivers form alluvial fans, flood plains, deltas, and on the bottom of lakes and the sea floor. The wind may move large amounts of sand and other smaller particles. Glaciers transport and deposit great quantities of usually unsorted rock material as till.
These deposited particles eventually become compacted and cemented together, forming clastic sedimentary rocks. Such rocks contain inert minerals which are resistant to mechanical and chemical breakdown such as quartz, zircon, rutile, and magnetite. Quartz is one of the most mechanically and chemically resistant minerals.
Biogenic sedimentary rocks
Biogenic sedimentary rocks contain materials generated by living organisms, and include carbonate minerals created by organisms, such as corals, molluscs, and foraminifera, which cover the ocean floor with layers of calcite which can later form limestone. Other examples include stromatolites, the flint nodules found in chalk (which is itself a biogenic sedimentary rock, a form of limestone), and coal(derived from the remains of tropical plants and subjected to pressure).
Precipitate sedimentary rocks
Precipitate sedimentary rocks form when mineral solutions, such as sea water, evaporate. Examples include the evaporite minerals halite and gypsum.
Other information
Sedimentary rocks are economically important in that they can be used as construction material. In addition, sedimentary rocks often form porous and permeable reservoirs in sedimentary basins in which petroleum and other hydrocarbons can be found.
It is believed that the relatively low levels of carbon dioxide in the Earth's atmosphere, in comparison to that of Venus, is due to large amounts of carbon being trapped in limestone and dolomite sedimentary layers. The flux of carbon from eroded sediments to marine deposits is known as the carbon cycle.
The shape of the particles in sedimentary rocks has an important effect on the ability of micro-organisms to colonize them. This interaction is studied in the science of geomicrobiology. One measure of the shape of these particles is the roundness factor, also known as the Krumbein number after the geologist W. C. Krumbein.
Arenite is a general term for sedimentary rock with sand-sized particles.
See also
- Sediment
- List of minerals
- List of rocks
Category:Petrology
Category:Sedimentary rocks
ja:堆積岩
th:หินตะกอน
StratigraphyStratigraphy, a branch of geology, is basically the study of rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. The subject was essentially invented and first rigorously applied by William Smith in England in the 1790s and early 1800s. Smith, known as the Father of English Geology, created the first geologic map of England and first recognized the significance of strata or rock layering.
Stratigraphy includes two related subfields: lithologic or lithostratigraphy and biologic stratigraphy or biostratigraphy.
Lithologic stratigraphy
See also: Lithostratigraphy
Lithostratigraphy, or lithologic stratigraphy, is the most obvious. It deals with the physical lithologic or rock type change both vertically in layering or bedding of varying rock type and laterally reflecting changing environments of deposition, known as facies change. Key elements of stratigraphy involve understanding how certain geometric relationships between rock layers arise and what these geometries mean in terms of depositional environment. One of stratigraphy's basic concepts is codified in the Law of Superposition, which simply states that, in an undeformed stratigraphic sequence, the oldest strata occur at the base of the sequence.
Chemostratigraphy is based on the changes in the relative proportions of trace elements and isotopes within and between lithologic units. Carbon and oxygen isotope ratios vary with time and are used to map subtle changes in the paleoenvironment This has led to the specialized field of isotopic stratigraphy.
Cyclostratigraphy documents the often cyclic changes in the relative proportions of minerals, particularly carbonates, and fossil diversity with time, related to changes in palaeoclimates.
Biostratigraphy
See also: Biostratigraphy
Biostratigraphy or paleontologic stratigraphy is based on fossil evidence in the rock layers. Strata from widespread locations containing the same fossil fauna and flora are correlatable in time. Biologic stratigraphy was based on William Smith's principle of faunal succession, which predated, and was one of the first and most powerful lines of evidence for, biological evolution. It provides strong evidence for formation (speciation) of and the extinction of species. The geologic time scale was developed during the 1800s based on the evidence of biologic stratigraphy and faunal succession. This timescale remained a relative scale until the development of radiometric dating, which gave it and the stratigraphy it was based on an absolute time framework, leading to the development of chronostratigraphy.
One important development is the Vail curve, which attempts to define a global historical sea-level curve according to inferences from world-wide stratigraphic patterns. Stratigraphy is also commonly used to delineate the nature and extent of hydrocarbon-bearing reservoir rocks, seals and traps in petroleum geology.
Archaeological stratigraphy
See also: Archaeological stratigraphy
In the field of archaeology, soil stratigraphy is used to better understand the processes that form and protect archaeological sites. The law of superposition holds true, and this can help date finds or features from each context, as they can be placed in sequence and the dates interpolated. Phases of activity can also often be seen through stratigraphy, especially when a trench or feature is viewed in section (profile). As pits and other features can be dug down into earlier levels, not all material at the some absolute depth is necessarily of the same age, but close attention has to be paid to the archeological layers. The Harris-matrix is a tool to depict complex stratigraphic relations, as they are found, for example, in the contexts of urban archaeology.
See also
- Stratification
- Sequence stratigraphy
- Important publications in stratigraphy
External links
- [http://strata.geol.sc.edu/ University of South Carolina Sequence Stratigraphy Web]
- [http://snobear.colorado.edu/Markw/Mountains/03/week9.html Front Range stratigraphy]
- [http://www.stratigraphy.org International Commission on Stratigraphy]
- [http://www.uga.edu/~strata/ University of Georgia (USA) Stratigraphy Lab]
Category:Geology
Category:Stratigraphy
Category:Methods and principles in archaeology
Topography
Topography, a term in geography, has come to refer to the "lay of the land", or the physiogeographic characteristics of land in terms of elevation, slope, and orientation. "Terrain" is a similar concept, used more to describe the land itself than the study of it. "Relief" is often used to refer to the third dimension of a map whether in actuality (as in a "raised relief" map, or drawn, as with contours, hachures or shading) or the territory it describes.
shading
Topography is similar to topology, popularly thought of as the mathematical study of surfaces. This may help explain its adoption in the world of geographers. Its actual original meaning, from Greek "topos" (place) and "graphein" (to draw), relates to the description of places rather than broad regions, in topographic surveys. Most 18th and early 19th century national surveys did not record relief across the entire area of coverage, calculating only spot elevations at survey points. The United States Geological Survey (USGS) topographical survey maps included contour representation of relief, and so maps that show relief, especially with exact representation of elevation, came to be called topographic maps (or "topo" maps) in the United States, and the usage has spread internationally.
The understanding of topography is critical for a number of reasons. In terms of environmental quality, agriculture, and hydrology, understanding the topography of an area enables the understanding of watershed boundaries, drainage characteristics, water movement, and impacts on water quality.
Understanding topography also impinges on soil conservation, especially in agriculture. Contour plowing is an established practice of enabling sustainable agriculture on sloping land, and is the practice of plowing along topographic lines.
Topography is critical militarily because it determines the ability of armed forces to take and hold areas, and to move troops and material into and through areas.
Topography is important in determining weather patterns. Two areas in fairly close proximity geographically may differ radically in characteristics such as precipitation because of elevation differences or because of a "rain shadow" effect.
Tectonic processes and erosional processes are the determiners of topography. Tectonic processes such as orogenies cause land to be elevated, and erosional (and weathering) processes cause land to be worn away to lower elevations.
See also
- Geomorphology
- Landform
- bathymetry
Category:Geomorphology
Category:Cartography
Category:Physical geography
Category:Geology
Category:Earth sciences
ko:분류:지질학
ja:Category:地質学
th:Category:ธรณีวิทยา
Crisis? What Crisis?
Crisis? What Crisis? is the fourth album by progressive rock band Supertramp, released in 1975 (see 1975 in music).
__NOTOC__
Track listing
All songs written by Rick Davies and Roger Hodgson.
#"Easy Does It" - 2:18
#"Sister Moonshine" - 5:15
#"Ain't Nobody But Me" - 5:14
#"A Soapbox Opera" - 4:54
#"Another Man's Woman" - 6:16
#"Lady" - 5:24
#"Poor Boy" - 5:07
#"Just a Normal Day" - 4:02
#"The Meaning" - 5:23
#"Two of Us" - 3:27
Personnel
- Bob Siebenberg (also known as C. Benberg) - percussion, drums
- Rick Davies - keyboard, vocals
- John Helliwell - saxophone, vocals, woodwind
- Roger Hodgson - guitar, keyboard, vocals
- Dougie Thomson - bass
Production
- Producers: Ken Scott, Supertramp
- Mastering: Greg Calbi, Jay Messina
- Assistants: John Jansen, Ed Thacker
- Arranger: Richard Hewson
- Cover design: Fabio Nicoli, Paul Wakefield, Dick Ward
Charts
Album - Billboard (North America)
Category:Supertramp albums
Category:1975 albums
backup software download zasony Biuro Rachunkowe Kielce WAKACJE Gry Playstation |
|
|
|
