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Topic: Crust (geology)

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  Crust (geology) Summary
The crust of the Earth is composed mainly of basalt and granite.
The oceanic crust (sima) is 5 to 10 km thick and is composed primarily of a dark, dense rock called basalt.
Crust formation is linked to periods of intense orogeny or mountain building; these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana.
www.bookrags.com /Crust_(geology)   (2173 words)

 ScienceDaily: Geology Articles
The continental crust is the layer of granitic, sedimentary and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves.
On the Earth, the lithosphere includes the crust and the uppermost layer of the mantle (the upper mantle or lower lithosphere) which is joined...
In geology, a crust is the outermost layer of a planet.
www.sciencedaily.com /articles/earth_climate/geology   (583 words)

 Crust (geology)
The boundary between the crust and mantle is conventionally placed at the Mohorovicic discontinuity, a boundary defined by a contrast in seismic velocity.
The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick, and it is mostly composed of less dense rocks than is the oceanic crust.
Continental crust — The continental crust is the layer of granitic, sedimentary and metamorphic rocks which form the continents and the areas of shallow seabed close to...
www.sciencedaily.com /articles/c/crust_(geology).htm   (864 words)

  Inside the Earth [This Dynamic Earth, USGS]
The crust, the outermost layer, is rigid and very thin compared with the other two.
The thickness of the crust beneath continents is much more variable but averages about 30 km; under large mountain ranges, such as the Alps or the Sierra Nevada, however, the base of the crust can be as deep as 100 km.
Below the crust is the mantle, a dense, hot layer of semi-solid rock approximately 2,900 km thick.
pubs.usgs.gov /gip/dynamic/inside.html   (485 words)

 Crust - Palaeos   (Site not responding. Last check: )
In geology, a crust is the outermost layer of a planet, part of its lithosphere.
The oldest crust on Earth is the Narryer Gneiss Terrane in Western Australia at 3.9Ga, and certain parts of the Canadian Shield and the Fennoscandian Shield are also of this age.
Crust formation is linked to periods of intense orogeny or mountain building; these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana.
www.palaeos.org /Crust   (447 words)

 Highbeam Encyclopedia - Search Results for geology
In geology, the process of deposition of a solid material from a state of suspension or solution in a fluid (usually air or water).
In geology, any relatively flat surface of bedrock (exposed or lightly covered with soil or gravel) that occurs at the base of a mountain or as a plain having no associated mountain.
in geology, process of change in the structure, texture, or composition of rocks caused by agents of heat, deforming pressure, shearing stress, hot, chemically active fluids, or a combination of these, acting while the rock being changed remains essentially in the solid state.
www.encyclopedia.com /SearchResults.aspx?Q=geology&StartAt=31   (713 words)

 19-Archives   (Site not responding. Last check: )
Geology gives the strongest evidence of the Earth's radius expanding at a rate of 1 to 2 centimeters per year.
It led to a "Continental Crust Sphere" of a diameter of approximately 7000 kilometers.
The geosynclines are areas of early elongation with the crust in a state of labiality and the origins of the stripe-like areas of folding of the different eras.
expanding-earth.org /page_19.htm   (3794 words)

The existence of these magma lenses near a mid-ocean ridge suggests that the lower oceanic crust is formed from several smaller sources of magma rather than a single large pool located in the middle of the crust.
Unlike continental crust, which is very old and thick, oceanic crust averages 6-7 kilometers (3-4 miles) thick and is constantly being recycled at tectonic plate boundaries on the seafloor.
Crust is destroyed at subduction zones, where plates come together, and created at mid-ocean ridges, where plates are pulling apart, like the Juan de Fuca Ridge.
www.newswise.com /articles/view/514065/?sc=rssn   (762 words)

 Savage Earth: Hell's Crust
At the thinnest spots in the oceans, where new crust is created, it is only a few miles thick; on the continents, the crust averages about 20 miles thick.
The creation of crust at mid-ocean ridges "accounts for about ninety-five percent of the volcanic activity on Earth," says geophysicist Don Forsyth of Brown University, a principal investigator on the MELT project, which is conducting a detailed study of how melted rock flows from the mantle and into the spreading centers.
The new crust eventually cools, and over time it is pushed to the side by still more melted rock rising up from within the Earth, in a continuous process.
www.thirteen.org /savageearth/hellscrust   (1537 words)

 Referenced Glossary for Planetary Geology for Teachers
Continental crust The rocks of the continental crust underlie the continents; they are equivalent to sial, and range in thickness from about 35 km to as much as 60 km under mountain ranges.
The density of the upper layer of the continental crust is ~ 2.7 g/cm
Oceanic crust The oceanic crust underlies the ocean basins and is equivalent to the sima.
geology.isu.edu /wapi/Geo_Pgt/referenced_glossary_for_planetar.htm   (13369 words)

 Glossary   (Site not responding. Last check: )
Geology considers the physical forces that act on the Earth, the chemistry of its constituent materials, and the biology of its past inhabitants as revealed by fossils.
A branch of geology dealing with the broad architecture of the outer part of the Earth, that is, the regional assembling of structural or deformational features, a study of their mutual relations, origin, and historical evolution.
A structurally high area in the crust, produced by positive movements that raise or upthrust the rocks, as in a dome or arch.
museum.gov.ns.ca /fossils/glossary.htm   (2751 words)

 Danielle's Garden Service 1
The crust and upper mantle can be differentiated into two zones which are important in explaining many geological phenomena; comprising an outer rigid and strong lithosphere (0-70 km) underlain by a partially molten, weak asthenosphere (70-250 km).
Endogenetic processes driven by geothermal heat may cause the injection of new material; into the crust, or the spilling of molten magma onto the surface to form volcanoes and lava flows; and lead to earth movements producing large scale uplift, warping and folding.
Major vertical displacements of the crust and contained sediments to form fold mountains occur at plate mar ins, but movement occurs at distances away from plate boundaries in the form of gentle upwarping, so that plate surfaces are not totally inert regions.
www.daniellesgarden.org /dw-earth.htm   (4998 words)

 UCMP Glossary: Geology
The processes by which materials of the Earth's crust are worn away, loosened, or dissolved while being transported from their place of origin.
The Earth's crust which is formed at mid-oceanic ridges, typically 5 to 10 kilometers thick with a density of 3.0 grams per centimeter cubed.
A long, narrow crack in the entire thickness of the Earth's crust, which is bounded by normal faults on either side and forms as the crust is pulled apart; v.
www.ucmp.berkeley.edu /glossary/gloss2geol.html   (3545 words)

 WVGES Geology: Mountains
Oceanic crust is chemically similar to the underlying mantle, and is thinner and denser than continental crust.
According to the theory of sea-floor spreading, new ocean crust is formed by the injection of liquid and solid rocks from the underlying mantle into fractures along mid-ocean ridges (Figure 7).
As new crust moves away from the axis of the mid-ocean ridge, it fuses with the part of the mantle that overlies the athenosphere and becomes part of the lithosphere (Figures 1 and 7).
www.wvgs.wvnet.edu /www/geology/geolf001.htm   (2492 words)

 Lunar Geology   (Site not responding. Last check: )
Lunar Geology is the study of the moons crust, rocks, strata, etc. Lunar Geology tends to cover two broad areas of study; Maria (and/or Basins) and Highlands.
Primary elements: The lunar crust is composed of a variety of primary elements, including uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, aluminum and hydrogen.
The crust ranges from 38 miles (60 km) on the near side to 63 miles (100 km) on the far side.
lunar.arc.nasa.gov /printerready/science/geologys.html   (1495 words)

 Geology 100 Telecourse Introductory Lecture Part 1
The movement of the crust and earthquakes are a result of this convection.
New crust is formed at the divergent plate boundary as the magma lithifies into rock and pushes the older crust away from the fissure.
The oceanic crust has subducted far enough to be heated by the mantle and melt.
dl.ccc.cccd.edu /classes/telecourses/geology100/IntroLecture1.htm   (1207 words)

 Mechanical & Microbiotic Crusts - Utah Geological Survey
These crusts are formed by a thin upper coating of clay particles oriented parallel to the surface.
In contrast, microbiotic crusts are produced by living organisms and their by-products that bind together soil particles at, or very near, the ground surface.
Mechanical crust also greatly enhances resistance to wind erosion but is not nearly as effective in improving resistance to erosion by water.
geology.utah.gov /surveynotes/gladasked/gladcrusts.htm   (621 words)

 Volcanic and Geologic Terms
Blister: A swelling of the crust of a lava flow formed by the puffing-up of gas or vapor beneath the flow.
Its surface is often rough and blocky as a result of fragmentation of the cooler, outer crust during growth of the dome.
Plate Tectonics: The theory that the earth's crust is broken into about 10 fragments (plates,) which move in relation to one another, shifting continents, forming new ocean crust, and stimulating volcanic eruptions.
volcano.und.nodak.edu /vwdocs/glossary.html   (4560 words)

 Delamination of lower crust
The high densities of average lower crust contrast significantly with those of the lithospheric mantle and asthenosphere, and there is a strong tendency for the overthickened lithospheric keel to sink.
During sinking, the lower crust is likely to undergo partial melting producing liquids of TTG (Tonalitic, Trondhjemitic, Granitic) and adakitic affinity (e.g., Springer and Seck, 1997; Defant and Kepezhinskas, 2001; Zegers and van Keken, 2001; Xu et al., 2002).
In conclusion, the role of sinking lower crust and lithospheric mantle (and of basaltic material recycled back into the mantle in general) is critical to explaining the geochemical attributes in CFB, OIB and LIP magmas.
www.mantleplumes.org /LowerCrust.html   (3208 words)

 UGA-Geology Faculty-A.Patino-Douce   (Site not responding. Last check: )
We are studying the behavior of various rock types (muscovite schists, tonalites, basaltic eclogites) at pressures of 20 - 35 kbar, in order to understand the processes that take place during subduction of continental crust (as demonstrated by natural occurrences of ultra-high-pressure metamorphic rocks).
Geology, mineralogy and geochemistry of syn-orogenic anatectic granites from the Achiras Complex, Córdoba, Argentina: some petrogenetic and geodynamic implications.
Anatexis and metamorphism in tectonically thickened continental crust exemplified by the Sevier hinterland, western North America.
www.gly.uga.edu /apatino.html   (930 words)

 Geology 100 Telecourse Introductory lecture Part 2
When the ice melts, the weight is removed from the crust and the crust rebounds (rises towards its original position where it is not pushing as far into the mantle.
Lithosphere -- Is rigid and is composed of the Crust + Uppermost Mantle
The lithosphere is solid and consists of the crust and uppermost mantle.
dl.ccc.cccd.edu /classes/telecourses/geology100/IntroLecture2.htm   (2026 words)

 Researchers model Earth's crust, geology - Minnesota Daily
Dubbed the "Jurassic Tank," the experimental basin is the first in the world to use a "sinking floor," which enables researchers to reproduce geologic effects and events that have occurred throughout Earth's history.
Geology professor Chris Paola said the tank will greatly enhance understanding about the Earth's crust and the movement of tectonic plates, which are segments of the crust.
The membrane represents the upper portion of the tectonic plate, and the underlying gravel represents the lower portions of the crust.
www.mndaily.com /articles/1998/07/10/7514   (804 words)

 New ideas on the formation of granite plutons in the crust   (Site not responding. Last check: )
Large granitic plutonic bodies are common in the upper part of the continental crust and it is generally believed that the magma from which these bodies originate is formed much lower down, probably at the base of the crust.
Most geology textbooks describe the mechanism of granite pluton emplacement in terms of the very slow (millions of years) ascent of a large bodies (diapirs) of magma.
The magma is emplaced in the upper crust (within kilometres of surface) by lateral spread along planes of weakness, and then by vertical thickening.
www.mala.bc.ca /~earles/granite-dec00.htm   (500 words)

 Ocean AdVENTure! - Geology
ydrothermal vents form when seawater seeps into cracks in the earth's crust, becomes superheated by magma, picks up and loses minerals on its way, then rises and bursts out into the ocean again through holes in the seafloor.
Sometimes the plates come together until one slips under the other, or subducts, to be recycled in the magma; both deep ocean trenches and high mountains are formed in the process.
Oceanic crust is usually basalt, while continental crust is lighter but thicker granite.
library.thinkquest.org /18828/data/geology.html   (449 words)

 Crust (geology)
Includes the geology of the state by province (descriptions, diagrams, maps, photographs, and geologic history of the Appalachian Plateau, Valley and Ridge, Blue Ridge, Piedmont, and Atlantic Coastal Plain provinces) and special topics such as natural hazards and geology of historic places.
Planetary Geology is the study of the origin, evolution, and distribution of matter condensed in the form of planets, satellites, comets and asteroids.
Research on geology and extraction of petroleum, coal and associated methane, hydrology and sedimentology of the Carpathian region.
omniknow.com /common/wiki.php?in=en&term=Crust_(geology)   (1901 words)

 USGS Geology in the Parks
The crust is the thin, solid, outermost layer of the Earth.
The crust is thinnest beneath the oceans, averaging only 5 kilometers thick, and thickest beneath large mountain ranges.
Continental crust (the crust that makes up the continents, of course!) is much more variable in thickness but averages about 30-35 km.
geology.wr.usgs.gov /parks/pltec/index.html   (386 words)

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