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Topic: Continental plates

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Oceanic crust

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	Plate tectonics - Wikipedia, the free encyclopedia
		The plates are around 100 km (60 miles) thick and consist of two principal types of material: oceanic crust (also, although perhaps an archaic reference in geology, called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium).
		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 - Search View - MSN Encarta
		The theory of plate tectonics was formulated during the early 1960s, and it revolutionized the field of geology.
		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.
		As a transform plate boundary cuts perpendicularly across the edges of the continental crust near the borders of the continental and oceanic crust, the result is a system such as the San Andreas transform fault system in California.
	encarta.msn.com /text_761554623__1/Plate_Tectonics.html (3862 words)

	Tectonic Plates
		Plate thickness is also highly variable, ranging from less than 15 km at the oceanic ridges to over 200 km beneath the Himalayan Mountains.
		According to plate tectonic theory, the outer 400 km of the Earth is is broken into two zones, the upper, thinner, rigidly deforming lithosphere 100 km or less in thickness and the lower ductilely deforming asthenosphere.
		There are three types of plate boundaries: 1) those composed of the tectonic plates that are moving apart, 2) those composed of tectonic plates that are slipping sideways, one past the other, and 3) those composed of tectonic plates that are colliding or being pushed together.
	www.utexas.edu /tmm/npl/mineralogy/Mineral_Genesis/defintectonicplates.htm (425 words)

	Plate tectonics - Facts, Information, and Encyclopedia Reference article
		Plate tectonics (from the Greek word for "one who constructs", τεκτων, tekton) is a theory of geology developed to explain the phenomenon of continental drift, and is currently the theory accepted by the vast majority of scientists working in this area.
		Plate tectonic theory arose out of two separate geological observations: continental drift, noticed in the early 20th century, and seafloor spreading, noticed in the 1960s.
		Plate motion is driven by the higher elevation of plates at mid-ocean ridges.
	www.startsurfing.com /encyclopedia/p/l/a/Plate_tectonics.html (4032 words)

	Continental drift - EvoWiki (Site not responding. Last check: 2007-11-01)
		Continental drift is the theory that the Earth's crust is divided into plates that move relative to each other, with their interactions producing a variety of geological features.
		Plate tectonics is the study of the causes and effects of these processes.
		The modern concept of continental drift was first proposed by German meteorologist Alfred Wegener; he pointed out the biogeographical details that Suess had pointed out, and he pointed out that Permian glaciers in the southern continents had flowed from oceans -- unless those continents had been united to form Gondwana back then.
	wiki.cotch.net /index.php/Continental_drift (870 words)

	Encyclopedia
		The boundaries between the plates are of three types: midocean ridges, where plates diverge; deep-sea trenches, or “subduction” zones, where two plates converge and one dives under the other; and transform, or “strike-slip,” faults, where plates slide past each other.
		The plate boundaries are zones of tectonic activity, where earthquakes and volcanic eruptions tend to occur.
		The theory of plate tectonics continues to be debated, tested, and expanded and has become both a paradigm and a center of controversy for the geological sciences.
	www.historychannel.com /encyclopedia/article.jsp?link=FWNE.fw..pl094800.a (1871 words)

	Chapter 5.2 Notes
		Continental crust is less dense, made of granite and rhyolite.
		Continental plates - 6 continental plates - mostly continental crust - have one continent and some oceanic crust.
		Oceanic-continental: the oceanic plate is denser and subducts (dives) under the continental plate.
	www.angelfire.com /nj/PflommScience/chap5notes2.htm (297 words)

	Speed of the Continental Plates
		Plate tectonics is a relatively new theory in the field of geology.
		This theory of plate tectonics replaced the previous one of continental drift, where it was thought that just the continents themselves drifted over the earth's surface.
		The majority of the research showed that the plates moved at the average rates between approximately 0.60 cm/yr to 10 cm/yr.
	www.hypertextbook.com /facts/ZhenHuang.shtml (712 words)

	Tectonic Plates
		Where an oceanic plate collides with a continental plate, the oceanic plate tips down and slides beneath the continental plate forming a deep ocean trench (long, narrow, deep basin.) An example of this type of movement, called subduction, occurs at the boundary between the oceanic Nazca Plate and the continental South American Plate.
		Plate tectonics, the branch of science that deals with the process by which rigid plates are moved across hot molten material, has helped to explain much in global-scale geology including the formation of mountains, and the distribution of earthquakes and volcanoes.
		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).
	www.webspawner.com /users/thecosyslughutt/tectonicplates.html (2216 words)

	The Remarkable Ocean World: The Library: Pele, the Hawaiian Fire Goddess
		Plate boundaries are where the action is. This is where the driving forces of plate tectonics takes place, and these boundaries are the source of most of the earthquakes of the world.
		The subduction of oceanic plates beneath continental plates is also believed to be responsible for creating the "Ring of Fire," a circle of active volcanoes, including Mt. Saint Helens and Mammoth Mountain, that span the boundaries of the Pacific Plate.
		Because continental lithosphere is relatively light, these plate boundaries tend to "reach for the sky." As one continent pushes against the other, the buoyant forces of both tend to cause the continents to push upwards.
	www.cbv.ns.ca /sarty/ocean11/plates.html (3406 words)

	Tectonic Boundaries (Site not responding. Last check: 2007-11-01)
		Oceanic plates are always subducted under a continental or oceanic plate and this region is known as a subduction zone (Bowler, 1998).
		The age of oceanic plates are separated into bands(the width of which indicates the amount of volcanism for that period of time), with equal ages between two corresponding bands separated by the oceanic ridge.
		A continental rift is produced primarily because convection in the earth's interior produces a bulging effect on the continental surface and this type of pressure eventually causes the rigid, brittle surface to fracture.
	kjett.bol.ucla.edu /plates6.htm (735 words)

	ATMOS 211
		Plate tectonics (plate structure) is a coherent theory of massive crustal rearrangement based on the movement of continent-sized lithospheric plates, developed in the 1960's.
		In convergence, plates moving in opposite directions meet, and the result of the collision normally is a vast crumpling of the edges as one plate subducts under the other.
		Plate tectonics is the theory that the Earth is made up of thin, rigid plates that move relative to each other.
	www.atmos.washington.edu /2001Q1/211/Group_projects/group_B_F00 (1861 words)

	Geotimes - December 2002 - Plate Forces
		Slabs are the leading edges of subducting plates, and they generate a tremendous amount of energy as they dive into the mantle.
		Since oceanic plates are thinner and denser than continental plates, a collision between the two results in the ocean plate subducting, with its leading edge forming the downgoing slab.
		Ever since plate tectonic theory took hold in the 1960s, geoscientists have argued over what drives plates: mantle upwelling at ridges that pushes plates apart, mantle circulation that drags plates along, or slab forces.
	www.agiweb.org /geotimes/dec02/NN_plates.html (549 words)

	What happens at plate boundaries- HW packet
		A continental plate rides over the edge of an oceanic plate because the continental plate is less dense.
		When an oceanic plate collides with a continental plate, the continental plate rides over the edge of the oceanic plate because the continental plate is less dense--even though it is thicker.
		In such collisions, neither plate is subducted, and the edges of the continents thicken greatly and push upward as they are forced together.
	www.ksellars.demon.co.uk /ifassign7.html (725 words)

	Have the continents drifted? - ChristianAnswers.Net
		Deformation occurs at the edges of the plates by three types of horizontal motion: extension (or rifting, moving apart), transform faulting (horizontal slipping along a fault line), and compression, mostly by subduction (one plate plunging beneath another).
		Plate collisions would have pushed up mountains, while cooling of the new ocean floor would have increased its density, causing it to sink and thus deepen the new ocean basins to receive the retreating flood waters.
		Some creationists believe that continental drift occurred rapidly by some mechanism(s), not now operative, at the close of the Flood or as a separate post-Flood catastrophe (e.g., when Genesis 10:25 says that in Peleg's day the earth was divided, meaning, in their view, continental drift rather than the division at Babel).
	www.christiananswers.net /q-aig/aig-c001.html (3344 words)

	Mountain building under the microscope: Most geologists think colliding continental plates caused earthquakes, which in ...
		In the theory of plate tectonics, the surface of the Earth is made of plates of lithosphere-crust and upper mantle-that continually shift their positions.
		The plates are rigid, so places within a plate move as one; the rocks there do not have to stretch or crumple.
		The movement between two plates is apparent at their edges; the world's volcanoes and earthquakes cluster along the plate boundaries.
	www.newscientist.com /article/mg13017645.300.html (337 words)

	Bryce Canyon National Park: GEODETECTIVE Program
		The crust of the Earth is divided into plates that move relative to one another.
		Continental crust is much lighter, or less dense, than oceanic crust.
		If there is little motion in the "plates", try separating the "plates" from the rest of the wax by cutting simple straight boundaries to separate the "plates" from the excess "crust".
	www.nps.gov /brca/geodet/geodet_crust.html (1264 words)

	My Plates Faster Than Your Plate
		This investigation focuses on the concepts of plate tectonics, including: the causes of these motions; directions and rate of movement; understanding of the three types of plate boundaries and their consequences (e.g.
		A tectonic plate is a massive slab of solid rock made of both continental and oceanic lithosphere.
		Notice that the ocean plate is subducting under the continental crust into the hot asthenosphere where it will melt and eventually become new lithosphere at a spreading zone.
	education.gsfc.nasa.gov /experimental/all98invProject.Site/Pages/trl/inv4-4.abstract.html (2603 words)

	Plate Tectonic Map of the Earth (Site not responding. Last check: 2007-11-01)
		The outer surface of the earth is made of 12 major plates and several smaller plates.
		These plates move towards each other (convergent boundaries), away from each other (spreading or divergent boundaries) or slide past each other (transform boundaries).
		Volcanoes are associated with convergent boundaries, where ocean plates are subducted under ocean or continental plates, with spreading boundaries, where new ocean plates are created, and with hot spots.
	volcano.und.nodak.edu /vwdocs/volc_images/tectonic_plates.html (92 words)

	EARTHQUAKES TREMORS AND SEIZMIC ACTIVITY IN THE EARTH'S CRUST OR CONTINENTAL PLATES \| HURRICANES TORNADOES BAD WEATHER ...
		Scientists proposed the idea of plate tectonics to explain a number of peculiar phenomenon on earth, such as the apparent movement of continents over time, the clustering of volcanic activity in certain areas and the presence of huge ridges at the bottom of the ocean.
		Plates can push together - If the two plates are moving toward each other, one plate typically pushes under the other one.
		At some boundaries where two plates meet, neither plate is in a position to subduct under the other, so they both push against each other to form mountains.
	www.solarnavigator.net /earthquakes.htm (813 words)

	Diamond - Wikipedia, the free encyclopedia
		Under continental crust, diamonds form starting at depths of about 150 kilometers (90 miles), where pressure is roughly 5 gigapascals and the temperature is around 1200 degrees Celsius (2200 degrees Fahrenheit).
		Diamonds have also rarely been found in deposits left behind by glaciers (notably in Wisconsin and Indiana); however, in contrast to alluvial deposits, glacial deposits are not known to be of significant concentration and are therefore not viable commercial sources of diamond.
		Diamonds can also be brought to the surface through certain processes which may occur when two continental plates collide and deeply formed rock is thrust to the surface, although this phenomenon is less understood and currently assumed to be uncommon.
	en.wikipedia.org /wiki/Diamond (9357 words)

	Lithospheric Plates
		Lithospheric plates are the plates that comprise the fractured surface of the earth.
		Lithospheric plates are of two types: continental plates comprised mostly of granitic-type rock rich in silica and aluminum (also called "sial") and oceanic plates comprised mostly of basaltic-type rocks rich in magnesium and aluminum (also called "sima").
		Earthquake and volcanic activity is common along the boundaries of lithospheric plates.
	www.uwsp.edu /geo/faculty/ritter/glossary/l_n/lithospheric_plates.html (73 words)

	Plate Tectonics (Site not responding. Last check: 2007-11-01)
		Where plates separate, molten rock from the mantle rises to fill the rifts.
		Where a continent and an ocean collide, the lighter continental plate goes over the heavier oceanic plate, which descends into the mantle.
		Where two plates slide past each other, friction accumulates, and fault lines with intense earthquakes develop in the area of the friction.
	members.tripod.com /~jeffbower/plates.html (174 words)

	GLY220 Class Notes
		- continental arc - andesitic to felsic volcanism and plutonism
		Tiny pieces of continental or thickened ocean crust ride on ocean plates and accrete to continental margins.
		Basically, plates move because the mantle is hot, plastic, dynamic and moving due to convection, while the surface (lithosphere) is cold, elastic and brittle, and responds to the underlying dynamo.
	www.uky.edu /AS/Geology/howell/220/notes02-plates-Spring-2006.html (1526 words)

	Volcano (Site not responding. Last check: 2007-11-01)
		Although there are numerous volcanoes (some very active) on the solar system's rocky planets and moons, on Earth at least, this phenomenon tends to occur near the boundaries of the continental plates.
		For example, Mount St. Helens is found inland from the margin between the oceanic Juan de Fuca Plate and the continental North American Plate.
		Their magmas are typically "calc-alkaline" as a result of their origins in the upper parts of altered ocean plate materials, mixed with sediments, and processed through variable thicknesses of more-or-less continental crust.
	volcano.iqnaut.net (3495 words)

	Active and passive continental margins
		The continental plates are in motion, and literally bounce around on the surface like giant air hockey pucks.
		An active continental margin is found on the leading edge of the continent where it is crashing into an oceanic plate.
		Because of the mountainous terrain, most of the rivers are fairly short, and the continental shelf is narrow to non-existent, dropping off quickly into the depths of the subduction trench.
	jersey.uoregon.edu /~mstrick/AskGeoMan/geoQuerry26.html (333 words)

	Reference.com/Encyclopedia/Volcano
		On Earth, volcanoes tend to occur near the boundaries of crustal plates.
		Important exceptions exist in hotspot volcanoes, which occur at locations far from plate boundaries; hotspot volcanoes are also found elsewhere in the solar system, especially on its rocky planets and moons.
		Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes extinct after a while and a new volcano is then being formed as the plate shifts over the hotspot.
	www.reference.com /browse/wiki/Volcano (3423 words)

	TECTONIC PLATES
		Wegener had some excellent proof that his theory of continental drift was correct.
		However, he was unable to come up with the force that actually moved these gigantic continental plates (about 2 centimeters a year).
		It’s the theory of plate tectonics, which explains the movement of these awesome and giant plates.
	home.mindspring.com /~cms-stuff/id3.html (915 words)

	Top 20 Encyclopedia (Site not responding. Last check: 2007-11-01)
		A volcano is a geological landform (usually a mountain) where magma (rock of the Earth's interior made molten or liquid by extremely high temperatures along with a reduction in pressure and/or the introduction of water or other volatiles) erupts through the surface of the planet.
		Volcanoes are usually situated either at the boundaries between tectonic plates or over hotspots.
		Most volcanoes on the land are formed at destructive plate margins: where oceanic crust is forced below the continental crust because oceanic crust is denser than continental crust.
	encyc.connectonline.com /index.php/Volcano (3718 words)

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