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Topic: Plate tectonics

	Plate Tectonics Earth Planet Model Patent
		Each plate member (12) is formed of a durable, lightweight plastic material and molded in raised and indented relief to illustrate such tectonic features as subduction zones, collision zones, mid-ocean ridges, island chains, island arcs, continental shelves, terrestrial and ocean floor topography, and the like.
		Plates (12) are attached to the exterior of a base globe (14) forming, as a whole, the surface layer of Earth, or lithosphere.
		Plate tectonics is quickly becoming the unifying, or central, theme of Earth science and geology school curriculum across the nation and, indeed, around the world.
	www.platetectonics.com /patent (1840 words)

	An Introduction to Plate Tectonics
		According to the plate tectonic model, the surface of the Earth consists of a series of relatively thin, but rigid, plates which are in constant motion.
		Plate movement takes place laterally away from the plate boundary, which is normall marked by a rise or a ridge.
		As one of the plates is subducted beneath the other it begins to melt at a depth of between 90 and 150 km and the resulting magma rises to the surface above the subduction zone to form a chain or arc of volcanoes.
	www.hartrao.ac.za /geodesy/tectonics.html (2104 words)

	Plate Tectonics
		Plate Tectonics is a theory developed in the late 1960s, to explain how the outer layers of the Earth move and deform.
		Plate tectonics has proven to be so useful that it can predict geologic events and explain almost all aspects of what we see on the Earth.
		The observation that the orogens are generally younger towards the outside of any continent suggests that the continents were built by collisions of plates that added younger material to the outside edges of the continents, and is further evidence that plate tectonics has operated for at least the last 2 billion years.
	www.tulane.edu /~sanelson/geol111/pltect.htm (3395 words)

	Plate tectonics - Wikipedia, the free encyclopedia
		Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology developed to explain the observed evidence for large scale motions within the Earth's crust.
		Where a dense oceanic plate collides with a less-dense continental plate, the oceanic plate is typically thrust underneath due to the greater buoyancy of the continental lithosphere, forming a subduction zone.
		The pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Pacific Ring of Fire) and moves much faster than the plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates.
	en.wikipedia.org /wiki/Plate_tectonics (5718 words)

	Plate Tectonics - MSN Encarta
		The theory of plate tectonics was formulated during the early 1960s, and it revolutionized the field of geology.
		Plate tectonics arose from an earlier theory proposed by German scientist Alfred Wegener in 1912.
		Tectonic plates are made of either oceanic or continental crust and the very top part of the mantle, a layer of rock inside the earth.
	encarta.msn.com /encyclopedia_761554623/Plate_Tectonics.html (598 words)

	Plate tectonics: a paradigm under threat
		According to the orthodox model of plate tectonics, the earth's outer shell, or lithosphere, is divided into a number of large, rigid plates that move over a soft layer of the mantle known as the asthenosphere, and interact at their boundaries, where they converge, diverge, or slide past one another.
		According to the seafloor-spreading hypothesis, new oceanic lithosphere is generated at midocean ridges ("divergent plate boundaries") by the upwelling of molten material from the earth's mantle, and as the magma cools it spreads away from the flanks of the ridges.
		In plate tectonics, the origin of marginal basins, with their complex crustal structure, has remained an enigma, and there is no basis for the assumption that some kind of seafloor spreading must be involved; rather, they appear to have originated by vertical tectonics (Storetvedt, 1997; Wezel, 1986).
	ourworld.compuserve.com /homepages/dp5/tecto.htm (13451 words)

	Plate Tectonics
		The movement of the plates is considered as the Plate Tectonic Theory.
		Tectonic forces, volcanoes and earthquakes all occur together and are interrelated.
		The Andes mountains of South America are the result of the partial melting of the plate being subducted, with the resultant molten rock (magma) rising through the continental crust and building a distinctive mountain chain down the length of that continent.
	rockhoundingar.com /geology/condrift.html (838 words)

	A Science Odyssey: You Try It: Plate Tectonics
		The thin shell represents the Earth's crust, divided into plates; within the shell is the firm but slippery mantle.
		The ensuing theory, known as plate tectonics, has had a major impact on Earth Sciences.
		If you are having trouble accessing the Plate Tectonics activity, try the non-Javascript version.
	www.pbs.org /wgbh/aso/tryit/tectonics (183 words)

	CVO Website - Plate Tectonics and Sea-Floor Spreading
		Each plate is about 80 kilometers (50 miles) thick and can be pictured as having a shallow part that deforms by elastic bending or by brittle breaking, and a deeper part that yields plastically, beneath which is a viscous layer on which the entire plate slides.
		In Washington State, the small Juan de Fuca plate off the coast of Washington, Oregon, and northern California is slowly moving eastward beneath a much larger plate that includes both the North American continent the land beneath part of the Atlantic Ocean.
		As the denser plate of oceanic crust is forced deep into the Earth's interior beneath the continental plate, a process known as subduction, it encounters high temperatures and pressures that partially melt solid rock.
	vulcan.wr.usgs.gov /Glossary/PlateTectonics/description_plate_tectonics.html (8248 words)

	Earth's Interior & Plate Tectonics
		Plate tectonics involves the formation, lateral movement, interaction, and destruction of the lithospheric plates.
		Continental rift valleys and vast plateaus of basalt are created at plate break up when magma ascends from the mantle to the ocean floor, forming new crust and separating midocean ridges.
		Plates collide and are destroyed as they descend at subduction zones to produce deep ocean trenches, strings of volcanoes, extensive transform faults, broad linear rises, and folded mountain belts.
	www.solarviews.com /eng/earthint.htm (1405 words)

	Plate Tectonics, the Cause of Earthquakes
		The plates consist of an outer layer of the Earth, the lithosphere, which is cool enough to behave as a more or less rigid shell.
		Plate boundaries in different localities are subject to different inter-plate stresses, producing these three types of earthquakes.
		The numerous north-south mountain ranges that dominate the landscape from Reno to Salt Lake City are the consequence of substantial east-west extension, in which the total extension may be as much as a factor of two over the past 20 million years.
	www.seismo.unr.edu /ftp/pub/louie/class/100/plate-tectonics.html (953 words)

	Earth's Continental Plates - ZoomSchool.com
		Over long periods of time, the plates also change in size as their margins are added to, crushed together, or pushed back into the Earth's mantle.
		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.
		Plate tectonics from the University of Tennessee (Knoxville).
	www.enchantedlearning.com /subjects/astronomy/planets/earth/Continents.shtml (1171 words)

	Earth Floor: Plate Tectonics
		The theory of plate tectonics has done for geology what Charles Darwin's theory of evolution did for biology.
		The plates are all moving in different directions and at different speeds (from 2 cm to 10 cm per year--about the speed at which your fingernails grow) in relationship to each other.
		The plates are moving around like cars in a demolition derby, which means they sometimes crash together, pull apart, or sideswipe each other.
	www.cotf.edu /ete/modules/msese/earthsysflr/plates1.html (198 words)

	Plate Tectonics
		crustal plates of the Earth are in horizontal motion.
		Of course, the timescale for convection in the pan is seconds and for plate tectonics is 10-100 million years, but the principles are similar.
		Thus, we see that differentiation is crucial to plate tectonics on the Earth, because it is responsible for producing an interior that can support tectonic motion.
	csep10.phys.utk.edu /astr161/lect/earth/tectonics.html (497 words)

	Plate Tectonics : Tectonic Plates
		While most plates are comprised of both continental and oceanic crust the giant Pacific Plate is almost entirely oceanic, and the tiny Turkish-Aegean Plate is entirely land.
		The relative small size of the numerous other plates neither diminishes their significance, nor their impact on the surface activity of the planet.
		The jostling of the tiny Juan de Fuca Plate, for example, sandwiched between the Pacific and North American Plate near the state of Washington, is largely responsible for the frequent tremors and periodic volcanic eruptions in that region of the country.
	www.platetectonics.com /book/page_2.asp (208 words)

	The ABC's of Plate Tectonics - Introduction
		Plate tectonics is now almost universally accepted, its mechanisms plausible and to a degree demonstrable.
		What IS presented is a broad analysis of the basic principles that should apply to the movements of plates, some new hypotheses about how they apply to convection and landform formation, and some expected scenarios for differing tectonic events.
		For those unfamiliar with the theory of plate tectonics, a separate page - The Basics of Plate Tectonics - is provided.
	webspinners.com /dlblanc/tectonic/ptABCs.php (276 words)

	The ABC's of Plate Tectonics - Introduction
		Plate tectonics is now almost universally accepted, its mechanisms plausible and to a degree demonstrable.
		What IS presented is a broad analysis of the basic principles that should apply to the movements of plates, some new hypotheses about how they apply to convection and landform formation, and some expected scenarios for differing tectonic events.
		For those unfamiliar with the theory of plate tectonics, a separate page - The Basics of Plate Tectonics - is provided.
	www.webspinners.com /dlblanc/tectonic/ptABCs.php (276 words)

	Plate Tectonics
		Plate tectonics is a unifying theory which helps us understand the underlying causes of the major topographic features of the Earth, as well as the reasons why some areas of the world are frequently devastated by earthquakes and volcanic eruptions.
		According to the theory of plate tectonics, the earth's surface (the rigid rocky layer of the lithosphere) is broken or divided into about a dozen "plates" that are moving relative to one another.
		Continental drift was the forerunner of the theory of plate tectonics.
	gpc.edu /~pgore/Earth&Space/GPS/platetect.html (2923 words)

	Plate Tectonics II
		As we saw in Plate Tectonics I, the concepts of continental drift and seafloor spreading had revolutionized geology, and researchers excitedly began to revise their interpretations of existing data.
		Since the densities of the two plates are similar, it is usually the older oceanic crust that is subducted because it is colder and slightly denser.
		A few boundaries defy simple classification and are referred to as "plate boundary zones." For example, a complicated earthquake pattern is produced by a wide, poorly understood plate boundary zone between the Eurasian and African plates in the Mediterranean region.
	www.visionlearning.com /library/module_viewer.php?mid=66 (1788 words)

	Plate Tectonics
		According to the theory of plate tectonics, the earth’s crust is broken up into at least a dozen rigid plates that move independently of one another.
		Where an oceanic plate is subducted beneath continental crust, the magma produced by subductive melting erupts from volcanoes situated among long, linear mountain chains, such as the Andes in South America.
		When an oceanic plate, such as the Nazca Plate which moves eastwards under the southeastern Pacific Ocean, meets a continental edge such as South America, the denser and heavier oceanic crust is normally subducted and partially melted beneath the continental plate.
	www.pacificislandtravel.com /nature_gallery/platetectonics.html (1320 words)

	Plate Tectonics
		These plates are continually shifting because the surface beneath them — the hot, soft mantle — is moving slowly like a conveyor belt, driven by heat and other forces at work in the Earth’s core.
		The plates are moving about a centimeter (0.5 in) to 15 centimeters (6 in) per year in different directions.
		As the plates move farther apart, magma from the Earth’s interior percolates up to fill the gap, sometimes leading to the eruption of undersea volcanoes.
	www.ocean.udel.edu /deepsea/level-2/geology/plate.html (624 words)

	Plate Tectonics
		Plate Boundaries - Tectonic plates interact in various ways as they move across the asthenosphere, producing volcanoes, earthquakes and mountain systems.
		The Pacific and Cocos plates are the fastest moving and the Arabian and southern African plates are slowest.
		Cold lithospheric plates are dense and tend to sink into the mantle, pulling the rest of the plate with it.
	www.geo.ua.edu /intro03/Plate.html (2149 words)

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