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Topic: Seafloor spreading

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Tectonics

Plate tectonics

Divergent boundary

Oceanic ridge

East Pacific Rise

Oceanic crust

Continental drift

Subduction

Lithosphere

Triple junction

Crust (geology)

Isostasy

Large igneous province

Asthenosphere

Deccan Traps

	Seafloor Spreading
		Youngest seafloor is red and as seafloor gets older it becomes yellow, green and then blue.
		The red sections are the newest area of the seafloor.
		Sometimes the oldest parts of the seafloor are next to land and sometimes they are near places where subduction is happening.
	www.windows.ucar.edu /tour/link=/earth/interior/seafloor_spreading.html&edu=elem (182 words)

	seafloor spreading - HighBeam Encyclopedia
		seafloor spreading theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges.
		Spreading is believed to be caused by far-field stresses, and the upwelling of the mantle beneath the spreading axis is the passive response to plate separation.
		The magnetic history of the earth is thus recorded in the spreading ocean floors as in a very slow magnetic tape recording, forming a continuous record of the movement of the ocean floors.
	www.encyclopedia.com /doc/1E1-seafloor.html (725 words)

	seafloor spreading
		The concept of seafloor spreading has been combined with that of continental drift and incorporated into plate tectonics.
		Seafloor spreading was proposed in 1960 by US geologist Harry Hess (1906–1969), based on his observations of ocean ridges and the relative youth of all ocean beds.
		It could then be shown that new rock forms continuously and spreads away from the ocean ridges, with the oldest rock located farthest away from the midline.
	www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0006336.html (325 words)

	Tectonic Pause: Towards the Unification of Earth Sciences - Karunakar Marasakatla
		Increased seafloor spreading and albedo with the thawing period of the cycle further melts the ice sheets.
		Reduced seafloor spreading and the gradual subsidence of the extinct mid-ocean ridges builds the pressure within the mantle and forms the plume under the crust depending on where the crust is going to breakup.
		Albedo and increased seafloor spreading with the thawing period of the cycle causes a global warming and melts the ice sheets.
	www.geocities.com /karunakarm/unifiedtheory.html (8181 words)

	Seafloor spreading - Wikipedia, the free encyclopedia
		Seafloor spreading is a part of the theory of plate tectonics; it is the process by which continental drift occurs.
		The Mid-Atlantic Ridge is a "textbook" slow spreading centre while the EPR is used as an example of fast spreading.
		It is still a matter of some debate whether seafloor spreading is driven primarily by the force of rising magma at these locations, or if it is driven by the force of sinking oceanic crust at subduction zones and these upwellings are merely a side effect.
	en.wikipedia.org /wiki/Seafloor_spreading (928 words)

	Seafloor spreading (Site not responding. Last check: 2007-10-30)
		Seafloor spreading is closely related to the theory of Plate Tectonics.
		Sea floor spreading was discovered in the 1960s by scientists who found that the age of the seafloor increases away from the spreading centers.
		That is, the seafloor near the spreading centers is relatively young and far away from the spreading centers the seafloor rocks are very old.
	www.newton.dep.anl.gov /askasci/gen99/gen99085.htm (221 words)

	Lost City Expedition: The Mid-Atlantic Ridge and Spreading
		Seafloor spreading is a very slow process, not much faster than the rate that fingernails or hair grows, but over millions of years this adds up.
		Today, the continents are about 3000 miles apart and seafloor spreading has kept up with their growing separation to make the rocks beneath the Atlantic Ocean.
		Seafloor spreading is one of the most important processes on our planet.
	www.lostcity.washington.edu /science/geology/midatlanticridge.html (388 words)

	EPS 102: Seafloor Spreading Lecture
		Evidence for seafloor spreading comes from magnetic field reversals recorded in rocks as they form along spreading centers.
		Magmatism on the seafloor isn't restricted to mid-ocean ridges.
		The depth to the ocean floor is proportional to the square root of age for ages 0 to 70 Ma.
	eps.berkeley.edu /cig/depaolo/eps102/PPT7_Seafloor_Spreading.html (256 words)

	Our Changing Continent
		Another concept critical to the development of the Theory of Plate Tectonics is seafloor spreading.
		As old crust was consumed in the trenches, new magma rose and erupted along the spreading ridges to form new curst.
		The continents, which are lighter than the ocean crust, glide over the surface of the Earth in response to the expansion and contraction along oceanic ridges.
	platetectonics.pwnet.org /story_tectonics/theory/seafloor_spreading.htm (613 words)

	lecture2
		Magma that extrudes to the ASC (the axial spreading center) taps a molten "lens" of magma roughly 1-2 km beneath the ASC.
		The locus of seafloor spreading is in the deep blue region (the axial valley) that is flanked by orange, topographically high flanks.
		Seafloor north of the transform fault moves to the west-southwest and seafloor south of the transform fault moves to the east-northeast.
	www.geology.wisc.edu /courses/g112/pl_tectonics.html (2923 words)

	OC/GEO 103 Lab 2
		Repeated cycles of cracking, spreading, melt injection, and solidification of new crust along mid-ocean ridges over long periods of time (tens to hundreds of millions of years) produces large plates of oceanic lithosphere that floor entire ocean basins.
		The distance from the crest of the mid-ocean ridge to the nearest continent is 2400 km.
		The rugged topography resulting from the deformation of the seafloor along transform faults is carried away with the spreading plates and forms inactive extensions of the transform faults, called fracture zones.
	oregonstate.edu /instruct/oc103/lab2.html (1436 words)

	plate tectonics - seafloor spreading
		Vine and Mathews hypothesis of seafloor spreading developed in 1960s on the basis of this kind of data.
		Simplified block diagram of seafloor spreading center with sediment and water removed, showing the 3 distinct igneous layers that form.
		Layers in oceanic crust and a model for the plumbing of spreading.
	maps.unomaha.edu /Maher/plate/week2/seafloor.html (887 words)

	seafloor spreading — Infoplease.com
		seafloor spreading: Role of the Spreading Center - Role of the Spreading Center In 1962 Hess proposed that the seafloor was created at mid-ocean...
		seafloor spreading: Discovery of the Mid-Ocean Ridges - Discovery of the Mid-Ocean Ridges Development of highly sophisticated seismic recorders and...
		The evolutionary puzzle of seafloor life: scientists are assembling critical pieces to reconstruct the history of life on the ocean......
	www.infoplease.com /ce6/sci/A0844184.html (282 words)

	Marine Magnetic Anomalies due to Seafloor Spreading: Current Models and Observations II - Geomagnetism and ...
		The skewness of marine magnetic anomalies due to seafloor spreading depends strongly on the direction of the paleomagnetic field as oceanic lithosphere is created and cooled.
		Seafloor spreading rates corrected for outward displacement agree better with instantaneous rates estimated from GPS-derived plate angular velocity vectors than do uncorrected long-term rates, underscoring the need to correct seafloor spreading rates for outward displacement before attempting to interpret differences between geodetic and geologic estimates of plate motions.
		With the new magnetic data it was possible to identify seafloor spreading anomalies between chrons 7 and 5A for a large area in the Central Pacific.
	www.agu.org /meetings/fm05/fm05-sessions/fm05_GP33B.html (2797 words)

	Dive and Discover : Mid-Ocean Ridge : Fast/Slow Spreading
		Steep steps in the seafloor that can be as tall as a few tens of meters (at fast spreading ridges) to hundreds of meters (at slow spreading ridges).
		These features are also called abyssal hills and are present on both sides of the ridge axis and are caused cracking of the ocean plate by seafloor spreading.
		Slow spreading ridges like the Mid-Atlantic Ridge generally have large, wide rift valleys, sometimes as big as 10-20 km wide and very rugged terrain at the ridge crest that can have relief of up to a thousand meters (3,128 feet).
	www.divediscover.whoi.edu /ridge/spreading.html (484 words)

	Developing the theory [This Dynamic Earth, USGS]
		As more and more of the seafloor was mapped during the 1950s, the magnetic variations turned out not to be random or isolated occurrences, but instead revealed recognizable patterns.
		By explaining both the zebralike magnetic striping and the construction of the mid-ocean ridge system, the seafloor spreading hypothesis quickly gained converts and represented another major advance in the development of the plate-tectonics theory.
		A profound consequence of seafloor spreading is that new crust was, and is now, being continually created along the oceanic ridges.
	pubs.usgs.gov /gip/dynamic/developing.html (1866 words)

	Caribbean VR
		This animation shows the breakup of Pangea and the pattern of seafloor spreading that created the Atlantic, Indian and Pacific Oceans during the last 150 million years.
		The colors in the animation illustrate both the age of the ocean floor and the symmetry of sea floor spreading.
		As the sea floor spreads, a symmetrical rainbow-colored pattern is produced.
	www.scotese.com /sfsanim.htm (470 words)

	Marine Magnetic Anomalies due to Seafloor Spreading: Current Models and Observations I Posters - Geomagnetism and ...
		The LRTPB is supposed to be a former left-lateral transform fault connecting the former southeast-dipping Manila Trench in the south and the northwest-dipping Ryukyu Trench in the north.
		The oldest age of the SCS oceanic crust identified in the northernmost SCS by marine magnetic anomalies indicates that the initiation of the SCS seafloor spreading occurred in the northeastern and southeastern corners.
		The spreading age younger towards southwest indicates that there was a SCS mid-ocean ridge propagation southwestward or a different stages of the SCS seafloor spreading; the SCS seafloor spreading occurred first in the east and then in the west.
	www.agu.org /meetings/fm05/fm05-sessions/fm05_GP23A.html (5554 words)

	06-058 (Seafloor spreading)
		The area had experienced an episode of seafloor spreading in 1991 and was being closely monitored as part of the RIDGE2000 program sponsored by the National Science Foundation.
		The seismometers are anchored to the seafloor by a mechanism that will release them and allow them to float to the surface when triggered by an acoustic signal.
		They found that the water over the spreading site was warmer and murkier than the surrounding seawater – just as it would have been had there been a recent eruption or spreading event.
	www.brown.edu /Administration/News_Bureau/2006-07/06-058.html (952 words)

	Seafloor Spreading (Site not responding. Last check: 2007-10-30)
		In seafloor spreading centers, magma from deep in the Earth forces its way up between two plates, pushing them apart.
		These spreading centers are often called mid-ocean ridges because many are found in the oceans and are usually higher than surrounding parts of the ocean floor.
		Scientists believe that a process similar to seafloor spreading may be responsible for some of the features on Europa's surface.
	www2.jpl.nasa.gov /galileo/wedges/seafloor.html (194 words)

	MODEL OF SEA-FLOOR SPREADING
		As spreading pulls the new oceanic crust apart, stripes of approximately the same size should be carried away from the ridge on each side (Fig.
		If sea-floor spreading operates, the youngest oceanic crust should be found at the ridges and progressively older crust should be found in moving away from the ridges towards the continents.
		sea-floor spreading — a hypothesis, proposed in the early 1960s, that new ocean floor is created where two plates move away from one another at mid-ocean ridges.
	www.ucmp.berkeley.edu /fosrec/Metzger3.html (2897 words)

	J Conder: ASP Plateau (Site not responding. Last check: 2007-10-30)
		The first is bathymetry (seafloor depth; scale in km) and the second is the calculated magnetization of the seafloor (from magnetic anomalies) draped over the bathymetry.
		The bands are narrower because until ~600ky ago, the spreading center was located to the northeast of its present location, creating the 'missing ' positively magnetized crust there rather than where the spreading center is now.
		However, the fracture zone is harder to reactivate further from the initial spreading center location (longer time to anneal), so it may have been easier to break a new transform on the platform rather than reactivate the strongest part of the inactive Amsterdam fracture zone.
	epsc.wustl.edu /~conder/research1.html (420 words)

	Seafloor Spreading, Part 1
		However, as little as 41 years ago the mechanism that the mid-oceanic ridges are a part of was only understood by a few geologists who were denounced by the majority of the geologists in the world.
		The concept that the Mid-Atlantic Ridge represents is referred to as seafloor spreading and was championed by a Princeton University geologist, Harry Hess (1906-1969).
		The new seafloor spreads away from the ridges eventually sinking into the deep ocean trenches found across the globe.
	www.suite101.com /article.cfm/everyday_geology/102057 (438 words)

	g02 Hess' hypothesis of seafloor spreading
		An observation that both models address is that beneath the relatively thin superficial cover of seafloor sediments (of an unconsolidated "Layer 1" and a consolidated, underlying "Layer 2" that thickens away from the ridge) is "Layer 3" which is a "uniform" 5-km thickness of seafloor crust that transmits seismic p-waves at 6.7 km/sec.
		When Hess spoke of his sea-floor spreading hypothesis in his Presidential address to the Geological Society of America in 1963, mutterings afterwards were, as recalled by Konrad Bates Krauskopf (1910-2003): "I don't really like that kind of geopoetry." For that, Hess himself had primed the pump.
		Earlier (in 1952) Edward Crisp Bullard (1907-1980) had explained that the oceanic heat flow was either due to convection or that Earth's mean chemical composition was the same, to a first approximation, in continental and oceanic areas when averaged down to depths of several hundred kilometers.
	geowords.com /histbooknetscape/g02.htm (1310 words)

	MAR: Introduction to the Mid-Atlantic Ridge
		The molten rock rises to the seafloor and cools to form the layer of crust that paves the ocean floor.
		The spreading centers themselves form broad central ridges that sink steadily with age and distance, starting at crestal heights of about 2,500 m water depth and sinking to typical open ocean depths of 4,000 meters or 12,000 feet.
		Once the load of the upper crust is removed from the lower crust, the balance of forces that act on the plate causes uplift of the high mountain.
	earthguide.ucsd.edu /mar/intro2.html (1078 words)

	5. Seafloor Spreading \| My Science Box
		Next students build a model illustrating seafloor spreading and discuss the magnetic and seafloor age data that support this model.
		Seafloor Spreading: Animation created by the US Geological Society.
		Seafloor Spreading with Magnetic Reversals: Animation courtesy of the US Geological Society.
	www.mysciencebox.org /seafloor (255 words)

	ScienceDaily: 'Anti-plume' Found Off Pacific Coast
		"There was an episode of seafloor spreading on a portion of the Juan de Fuca Ridge that was covered with about a hundred meters of sediment and what usually happens in that case is that lava erupts onto the ocean floor and hot fluid is expelled into the water.
		The earthquakes, most having a magnitude of 2.0 to 4.0, originate along the Juan de Fuca Ridge, a submarine mountain range 300 miles west of the Oregon coast that was formed by seafloor spreading or the movement of oceanic plates away from one another.
		Scientists Search For Seafloor Eruption (March 13, 2005) -- The most intense swarms of earthquakes detected in the last 10 to 12 years on the far edge of the Juan de Fuca plate could indicate the eruption of magma from the seafloor or an underwater volcano.
	www.sciencedaily.com /releases/2004/07/040715075917.htm (2346 words)

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