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Topic: Oceanic crust

Related Topics

Crust

Continental crust

Lithosphere

Subduction

Seafloor spreading

Subduction zone

Divergent boundary

Mantle (geology)

Plate tectonics

Pacific Plate

North American Plate

Rock (geology)

Earth

Continental shelf

Ocean

	AMNH - Spreading
		The change in bathymetry stems from the fact that old oceanic crust is cold and dense whereas new oceanic crust is warm and buoyant (less dense).
		Oceanic crust is therefore younger near the midocean ridges and increasingly older farther from the midocean ridges.
		The new crust is formed from molten rock or magma that rises from the mantle to fill the gap left between the plates as they separate.
	www.amnh.org /nationalcenter/expeditions/blacksmokers/spreading.html (567 words)

	Crust (geology) - Wikipedia, the free encyclopedia
		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.
	en.wikipedia.org /wiki/Crust_(geology) (435 words)

	Encyclopedia: Oceanic crust (Site not responding. Last check: 2007-11-05)
		The continental crust is the layer of granitic and sedimentary rock which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves.
		Oceanic crust is a lot thinner than Continental crust, being only between 7 and 10km thick.
		Oceanic crust is significantly younger than continental crust, this may be explained by subduction, as subduction continually recycles and recreates oceanic crust.
	www.nationmaster.com /encyclopedia/Oceanic-crust (476 words)

	Crust - Simple English Wikipedia
		The crust of a piece of bread is the edge where it is harder and darker.
		The crust is also the outermost layer of the earth.
		It is made up of two parts: continental crust and oceanic crust.
	simple.wikipedia.org /wiki/Crust (157 words)

	* Oceanic crust - (GIS): Definition
		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...
		Beyond the limit of continental crust, the offshore geology is represented by age of oceanic crust rather than the sedimentary cover, although a few isopachs are shown to indicate the thickness of the cover (Tucholke, 1986; Jackson and Oakey, 1988)...
		The thin parts are oceanic crust composed of dense (mafic) iron magnesium silicate rocks and underlie the ocean basins...
	en.mimi.hu /gis/oceanic_crust.html (154 words)

	The Earth's Crust (Site not responding. Last check: 2007-11-05)
		Oceanic crust underlies most of the two-thirds of the Earth's surface which is covered by the oceans.
		New oceanic crust is constantly being generated by sea-floor spreading at mid-ocean ridges, while other parts of the oceanic crust are being recycled into the mantle at subduction zones.
		Maps of oceanic crustal ages have been produced as a result of studies of the record of reversals of the Earth's magnetic field which is preserved in the crust as it forms.
	www.antarctica.ac.uk /Key_Topics/Geological_Evolution/earths_crust (556 words)

	Amazing Land...
		Oceanic crust, which lies under the oceans is thinner, denser and more active than continental crust.
		Seafloor spreading is the movement of two oceanic plates away from each other, which results in the formation of new oceanic crust from magma that comes from within the Earth's mantle along a a mid-ocean ridge.
		When a thin, dense oceanic plate collides with a relatively light, thick continental plate, the oceanic plate is forced under the continental plate; this phenomenon is called subduction.
	www.geocities.com /yingzyingz/land.htm (449 words)

	The EXPANDING EARTH - Geology (Site not responding. Last check: 2007-11-05)
		On that side is new oceanic crust with high heat flux and repeated horsts and grabens, in contrast with the eastern side characterized by seismic quiet and little disturbed sediment.
		The north-west Pacific's oceanic crust is largely of Jurassic age and hence, in an expansion interpretation, was extruded from the mantle at a Jurassic palaeo-radius, and a correspondingly higher surface curvature (quantitative modelling, of pre-Jurassic Earth indicates palaeo-radius ~50 % present).
		Oceanic crust forms directly from to the top of the mantle being exposed at mid ocean ridges as Earths' waxing internal expansion pulls the crust apart at submerged rifting fissures commonly called mid-ocean-ridges.
	www.geocities.com /CapeCanaveral/Launchpad/8098/1.htm (13217 words)

	10(j) Crustal Formation Processes (Site not responding. Last check: 2007-11-05)
		The movement of oceanic crust under the continents is the mechanism responsible for transporting the sedimentary materials found on the ocean floor to the edge of the continents.
		Plumes of magma from the Earth's asthenosphere are generated from the friction produced at the contact zone where oceanic crust slides past continental crust (Figure 10j-1).
		This process causes the oceanic crust to return to the mantle were it is re-melted into magma.
	www.geog.ouc.bc.ca /physgeog/fundamentals/10j.html (1036 words)

	Marine Geology: Plate Tectonics (Site not responding. Last check: 2007-11-05)
		Oceanic crust is the main crustal unit under Earth's oceans.
		Oceanic crust has lots of silica and iron and may be referred to as simatic.
		At oceanic ridges most of the crustal movement is near the surface as sea-floor spreading causes plates to move apart and new crust is formed by magma pushing up from the mantle.
	www.biosbcc.net /ocean/marinesci/02ocean/mgtectonics.htm (1914 words)

	The Structuring of the Earth's Crust (Site not responding. Last check: 2007-11-05)
		One important factor distinguishing oceanic lithosphere from continental lithosphere is that the former is significantly younger than the latter.
		The great difference between the ages of continental and oceanic lithosphere may be explained by the fact that subduction continually recycles oceanic lithosphere and so never has the opportunity to accumulate and age for billions of years.
		Oceanic lithosphere is primarily basaltic in composition and this is essentially due to its creation along oceanic ridges.
	kjett.bol.ucla.edu /plates4.htm (558 words)

	NEW VIEWS OF SEAFLOOR SPREADING FROM THE GEOLOGY OF OPHIOLITES AND OCEANIC CRUST: CONTINUALLY COLLAPSING CALDERAS TO ... (Site not responding. Last check: 2007-11-05)
		The current view of oceanic crust and upper mantle derives from an amalgamation of observations and ideas from marine geology and geophysics and field investigations of ophiolite complexes over the past 30 years.
		Crust generated at fast- to intermediate-spreading ridges (>30 m/yr half-rate) appears to have the expected layered sequence but with internal structures that were probably generated by continual caldera collapse above a more or less continuous magma chamber.
		Crust from slow-spreading ridges is highly variable and ranges from the expected layered sequence to highly dismembered assemblages.
	gsa.confex.com /gsa/2001AM/finalprogram/abstract_14305.htm (482 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.pbs.org /wnet/savageearth/hellscrust (1537 words)

	The Crust
		The material of which the oceanic crust consists is for the greater part tholeiitic basalt (this is basalt without olivine).
		The average density of the oceanic crust is 3g/cm³.
		The earth's crust is the thickest below the continents, with an average of about 20 to 25 miles (30 to 40 km) and with a maximum of 45 miles (70 km).
	mediatheek.thinkquest.nl /~ll125/en/crust.htm (571 words)

	What is the crust. (Site not responding. Last check: 2007-11-05)
		The crust is the outermost layer of the earth (not counting the atmosphere).
		The crust is relatively cold and brittle compared to the layers that are deeper down.
		Oceanic crust consists of young basalt, is about 5 km thick, and is presently forming at mid-ocean ridges.
	volcano.und.nodak.edu /vwdocs/frequent_questions/grp9/question88.html (159 words)

	Earth's Interior & Plate Tectonics
		The crust (both oceanic and continental) is the surface of the Earth; as such, it is the coldest part of our planet.
		The rigid, outermost layer of the Earth comprising the crust and upper mantle is called the lithosphere.
		New oceanic lithosphere forms through volcanism in the form of fissures at mid-ocean ridges which are cracks that encircle the globe.
	www.solarviews.com /eng/earthint.htm (1396 words)

	CVO Website - Plate Tectonics and Sea-Floor Spreading
		By contrast, oceanic crust is composed of basaltic rocks, which are much denser and heavier.
		As old oceanic crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new crust.
		This connection helps to confirmthe seafloor-spreading hypothesis by pin-pointing the zones where oceanic crust is being generated (along the ridges) and the zones where oceanic lithosphere sinks back into the mantle (beneath the trenches).
	www.uic.edu /classes/psych/psych353/role/plate.html (637 words)

	Earth's Continental Plates - ZoomSchool.com
		Oceanic crust (the thin crust under the oceans) is thinner and denser than continental crust.
		Under the crust is the rocky mantle, which is composed of silicon, oxygen, magnesium, iron, aluminum, and calcium.
		Seafloor spreading is the movement of two oceanic plates away from each other (at a divergent plate boundary), which results in the formation of new oceanic crust (from magma that comes from within the Earth's mantle) along a a mid-ocean ridge.
	www.enchantedlearning.com /subjects/astronomy/planets/earth/Continents.shtml (1171 words)

	RedOrbit - Science - New Images Reveal Different Magma Pools Form the Ocean's Crust (Site not responding. Last check: 2007-11-05)
		For the first time, scientists have produced images of the oceanic crust and found that the upper and lower layers of the crust are likely formed from different magma pools.
		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.
	www.redorbit.com /news/display?id=221547&source=r_science (778 words)

	Bryce Canyon National Park: GEODETECTIVE Program (Site not responding. Last check: 2007-11-05)
		The crust of the Earth is divided into plates that move relative to one another.
		The crust is ridged and brittle, and when it cracks or moves, earthquakes occur.
		This melted oceanic crust becomes less dense (because it is now in a liquid form) and therefore rises towards the surface causing continental crust to rise up above it, forming mountains and volcanoes.
	www.nps.gov /brca/geodet/geodet_crust.html (1264 words)

	Geography 3b: Geology Lectures
		B112[concept]: Continental-arc Subduction: When oceanic crust collides with continental crust, the effect is similar to an inflated raft upon a pool colliding wth a floating stick --the taller, lighter raft will override the shorter denser stick.
		The overridden oceanic crust subducts into the mantle where melts, and an arc of volcanoes forms inland of the subduction (ie., Andes Mountains).
		B115[concept]: Sea Floor Spreading: Diverging oceanic crust results in a seafloor spreading center --where new ocean crust is formed by the eruption of mafic material from the mantle (ie., The Mid-Atlantic Ridge).
	piru.alexandria.ucsb.edu /~tierney/lectures/geology.htm (1250 words)

	Understanding plate motions [This Dynamic Earth, USGS]
		As with oceanic-continental convergence, when two oceanic plates converge, one is usually subducted under the other, and in the process a trench is formed.
		Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate).
		Oceanic fracture zones are ocean-floor valleys that horizontally offset spreading ridges; some of these zones are hundreds to thousands of kilometers long and as much as 8 km deep.
	pubs.usgs.gov /publications/text/understanding.html (2502 words)

	Research reveals limitations of seismic data for mapping rock units in young oceanic crust
		The oceanic crust has been studied by geophysicists and geologists for many years—geophysicists using remote sensing techniques such as seismic exploration, and geologists with samples and direct observations.
		The problem with trying to reconcile the two models of the structure of oceanic crust is that while seismic methods can be used to probe deeply into the crust and gather data over unlimited distances, the interpretation of results is usually by inference.
		Because of the exposures at Hess Deep and the Blanco transform fault, the researchers were able to compare the seismic structure of upper oceanic crust with the known geology of the crust exposed and mapped by previous submersible dives.
	www.physorg.com /news89376738.html (1012 words)

	Search Results for oceanic - Encyclopædia Britannica
		Theory that oceanic crust forms along submarine mountain zones, known collectively as the oceanic ridge system, and spreads out laterally away from them.
		Oceanic trench area in which, according to the theory of plate tectonics, the seafloor underthrusts an adjacent plate, dragging the accumulated trench sediments downward into the Earth's upper mantle.
		Linear trough in the Earth's crust in which rocks of Late Precambrian to Mesozoic Age (roughly 600–65 million years ago) were deposited along the western coast of North America.
	www.britannica.com /search?query=oceanic&fuzzy=N&ct=gen1&iq=5&start=6&show=20 (365 words)

	Low-velocity oceanic crust at the top of the Philippine Sea and Pacific plates beneath the Kanto region, central Japan, ...
		Oceanic crust at the uppermost part of these subducting plates is a low-velocity layer.
		Low-velocity oceanic crust of the Philippine Sea plate subducts to a depth of approximately 80 km.
		We trace the subducting oceanic crust of the Pacific plate to a depth of ∼120 km.
	www.agu.org /pubs/crossref/2005/2005JB003673.shtml (371 words)

	Ocean 540: Oceanic Lithosphere; Plate Tectonics; Seafloor Topography
		In contrast the oceanic crust is more dense, thinner, and floats at lower elevation (and so is covered with water!).
		A passive margin between the ocean crust and continental margin is shown, i.e., the continent is also moving away from the ridge (the eastern seaboard of the United States is an example).
		The upper most lithosphere is the oceanic crust, which is constructed of melt from the mantle which is intruded into pre-existing crust and erupted onto the seafloor.
	www2.ocean.washington.edu /oc540/lec01-1 (1472 words)

	Lamont-Doherty Earth Observatory News (Site not responding. Last check: 2007-11-05)
		Ocean sediments, the crust and the Moho transition zone are clearly visible in these seismic reflection images taken near the Juan de Fuca Ridge (A).
		The Earth’s oceanic crust is formed from magma bodies located beneath mid-ocean ridges.
		The presence of such bodies that deep near a mid-ocean ridge suggests that the lower crust is at least partially formed from several smaller sources of magma rather than from a single large source located in the middle of the crust.
	www.ldeo.columbia.edu /news/2005/08_30_05.htm (509 words)

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