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Topic: Plate boundaries

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In the News (Tue 16 Jul 19)

  Plate tectonics - Wikipedia, the free encyclopedia
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.
Tectonic plates are comprised of two types of lithosphere: continental and oceanic lithospheres; for example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans.
Plate motion is driven by the higher elevation of plates at mid-ocean ridges.
en.wikipedia.org /wiki/Plate_boundaries   (4019 words)

 Plate Tectonic Theory: Plates and Interplate Relationships
It is possible a plate could be a continent alone, but for this to occur all edges of the continent would have to be a plate boundary (very rare, perhaps not practically possible).
Two divergent margins (plate boundaries) are present in the cross section, one labeled as such to the right of the continental craton, and the other on the left side.
But in the larger picture, it is common for a divergent plate boundary to come into existence and create a new ocean basin, and then for that ocean basin to close again along a convergent plate boundary until two continents collide.
csmres.jmu.edu /geollab/vageol/vahist/plates.html   (917 words)

 Plate boundaries
Plate boundaries are found at the edge of the lithospheric plates and are of three types,
This plays a key role in the development of plate tectonic theory because it was the first positive proof that the plates were indeed moving and had been for most of geologic time.
Another example of a transform boundary is seen at the mid-ocean ridges, where the spreading centers are offset by transform faults anywhere from a few meters to several kilometers in length.
scign.jpl.nasa.gov /learn/plate4.htm   (940 words)

 USGS Earthquake Hazards Program: Earthquakes and Plate Tectonics   (Site not responding. Last check: 2007-10-17)
Plate tectonics tells us that the Earth's rigid outer shell (lithosphere) is broken into a mosaic of oceanic and continental plates which can slide over the plastic aesthenosphere, which is the uppermost layer of the mantle.
One of the keys to plate tectonics was the discovery that the Earth's magnetic field has reversed its polarity 170 times in the last 80 million years.
We have seen that earthquakes occur at the following three kinds of plate boundary: ocean ridges where the plates are pulled apart, margins where the plates scrape past one another, and margins where one plate is thrust under the other.
wwwneic.cr.usgs.gov /neis/plate_tectonics/rift_man.html   (1346 words)

 Plate Tectonics : Plate Boundaries
As the giant plates move, diverging [pulling apart] or converging [coming together] along their borders, tremendous energies are unleashed resulting in tremors that transform Earth’s surface.
While all the plates appear to be moving at different relative speeds and independently of each other, the whole jigsaw puzzle of plates is interconnected.
When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed.
www.platetectonics.com /book/page_5.asp   (831 words)

 Plate Tectonics, the Cause of Earthquakes   (Site not responding. Last check: 2007-10-17)
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.
At compressional boundaries, earthquakes are found in several settings ranging from the very near surface to several hundred kilometers depth, since the coldness of the subducting plate permits brittle failure down to as much as 700 km.
www.seismo.unr.edu /ftp/pub/louie/class/100/plate-tectonics.html   (953 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)

 OptIPuter Outreach
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.
The zone between two plates sliding horizontally past one another is called a transform-fault boundary, or simply a transform boundary.
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).
education.sdsc.edu /optiputer/teachers/platemovement.html   (958 words)

 Comparing the Continents with Plate Boundaries
It is important that students begin to visualize or understand that the plates are a solid rock shell which includes both dry land and the "land" underneath the oceans.
Plates are composed of the Earth’s crust and upper mantle, which are collectively called the lithosphere.
When the strength of the rocks at the plate boundary is exceeded, they move rapidly, "catching up" with the rest of the plates.
www.msnucleus.org /membership/html/k-6/pt/plate/k/ptptk_3a.html   (504 words)

 A Science Odyssey: You Try It: Plate Tectonics: Intro
Plate tectonics is the theory that Earth's outer layer is made up of plates, which have moved throughout Earth's history.
Exactly what drives plate tectonics is not known.
Whatever drives the movement, plate tectonic activity takes place at four types of boundaries: divergent boundaries, where new crust is formed; convergent boundaries, where crust is consumed; collisional boundaries, where two land masses collide; and transform boundaries, where two plates slide against each other.
www.pbs.org /wgbh/aso/tryit/tectonics/intro.html   (256 words)

 ScienceMaster - JumpStart - Plate Motion
Plate boundary zones -- broad belts in which boundaries are not well defined and the effects of plate interaction are unclear.
Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle.
Even though the Nazca Plate as a whole is sinking smoothly and continuously into the trench, the deepest part of the subducting plate breaks into smaller pieces that become locked in place for long periods of time before suddenly moving to generate large earthquakes.
www.sciencemaster.com /jump/earth/plate_motion.php   (2550 words)

 Finding faults   (Site not responding. Last check: 2007-10-17)
Divergent plate boundary (usually found at mid-oceanic ridges): The plates move away from each other, and new rock solidifies from hot rock rising from the upper mantle.
Convergent plate boundary (found in the U.S. Pacific Northwest): The heavier oceanic plate "subducts" beneath the lighter continental plate.
At these divergent plate boundaries, hot rock called magma emerges and solidifies into solid rock, pushing the ocean floor in both directions away from the point of origin.
whyfiles.org /094quake/4.html   (631 words)

 Plate Tectonics - Discover Our Earth
Most people have heard of Plate Tectonics, even if they don't have a clear idea of what a "plate" is made of or what "tectonics" actually means.
(Plates are made of lithosphere; Tekton is Greek for carpenter, or builder, so tectonics refers to the building of mountains and other large-scale structures.) The earth's surface is covered with thin plates that are irregularly shaped and move independently from one another.
Because the plates are moving in different directions, there is bumping, jostling and sliding where two plates meet.
atlas.geo.cornell.edu /education/student/tectonics/boundaries_i.html   (134 words)

 Plate boundaries (from plate tectonics) --  Encyclopædia Britannica   (Site not responding. Last check: 2007-10-17)
As conceived by the theory of plate tectonics, the lithospheric plates are much thicker than the oceanic or the continental crust; their boundaries do not usually coincide with those between oceans and continents; and their behaviour is only partly influenced by whether they carry oceans, continents, or both.
These plates move relative to each other and interact at their boundaries, where they diverge, converge, or slip relatively harmlessly past one another.
Plate glass was first made in the 17th century in France, after which several improvements in the original batch technique culminated in the Bicheroux process (1918), in which the glass was received by power-driven rollers that then...
www.britannica.com /eb/article?tocId=14444   (1018 words)

 Plate Boundaries   (Site not responding. Last check: 2007-10-17)
Convergent boundaries come in three varieties depending upon the type of lithosphere that is juxtaposed across a subduction zone.
Hawaiian Islands form a linear chain of islands but they are located in the center of the Pacific plate and were not formed by subduction along a plate boundary.
Plates on either side of a transform boundary slide past each other without either plate being consumed and without a gap opening between the plates.
enterprise.cc.uakron.edu /geology/natscigeo/Lectures/ptectonics/pboundary.htm   (1166 words)

 An updated digital model of plate boundaries: PB2002   (Site not responding. Last check: 2007-10-17)
Boundary types are: CCB continental convergent boundary, CTF continental transform fault, CRB continental rift boundary, OSR oceanic spreading ridge, OTF oceanic transform fault, OCB oceanic convergent boundary, SUB subduction zone.
Boundaries (heavy colored lines) of the Aegean Sea (AS) and Anatolia (AT) plates, which are surrounded by the Africa (AF), Arabia (AR), and Eurasia (EU) plates.
Very large plates are limited in their area because of the finite area of the Earth, and perhaps also by mantle convection tractions.
element.ess.ucla.edu /publications/2003_PB2002/2003_PB2002.htm   (1405 words)

 A Lesson in Plate Tectonics
Plate margins are the edges of the plates, where all the awesome power of nature is released in earthquakes and volcanoes!
As a plate moves in one direction it collides with the adjacent plate on its "front" end, while the trailing end of the plate is being pulled and stretched (spreading) from the plate on the other end.
In many of these boundaries there is a lot of tension and strain where the two plates are sliding and scraping past each other.
www.extremescience.com /PlateTectonicsmap.htm   (794 words)

 Evidence for Plate Tectonics
The original conjectures concerning plate tectonics were based on circumstantial evidence like the shapes of continents being such that they would fit well if pushed together.
Plate tectonic motion, which may be only centimeters per century, is now being studied by careful laser ranging techniques that are capable of detecting such small motions.
If the crustal plates are pulling apart at boundaries like the Mid-Atlantic Ridge (see the line of earthquake epicenters down the center of the Atlantic in the preceding figure), the sea floor near these ridges should be very young geologically, since it is formed of material upwelling from the interior.
csep10.phys.utk.edu /astr161/lect/earth/evidence.html   (399 words)

 Plate Tectonics I
Boundaries were drawn at mid-oceanic ridges and subduction zones
Because the Indian Plate is still moving northward, the Himalayas are still rising at a rate of about 1 cm per year.
His continental drift theory was the first step in the development of plate tectonic theory, the foundation upon which modern geology is built.
www.visionlearning.com /library/module_viewer.php?mid=65   (1489 words)

 Plate boundaries
In a subduction boundary, one plate slips beneath the other, leading to the formation of a deep trench.
This slipping however generally doesn't happen smoothly - because of friction the plates remain in place for a while, building up a kind of stored potential energy from the forces trying to move them, and then this energy is released suddenly when the forces become too large.
A notable example of a transform boundary is the San Andreas fault in California.
theoryx5.uwinnipeg.ca /mod_tech/node193.html   (237 words)

 Plate Boundaries   (Site not responding. Last check: 2007-10-17)
The driving mechanism of plate tectonics is a network of convective heat currents, generated by the hot core of the earth and which circulate in the mantle.
The convective heat currents in the mantle impinge on the asthenosphere causing deformation and subsequent movement of the lithospheric plates.
In general you don't want to live near a plate boundary as the earth is active there.
zebu.uoregon.edu /1996/ph123/l13b.html   (385 words)

 GeoTopics @ GeoNet
The are two types of tectonic plates - continental plates and oceanic plates.
The point where two or more plates meet is known as a plate boundary.
Collision plate boundaries occur when two continental plates move towards each other.
www.bennett.karoo.net /topics/platetec.html   (250 words)

 ch4_Convergent Plate boundaries
Summary diagram of processes at a convergent plate boundary between an oceanic and continental plate.
Transform plate boundary - where plates slide past each other, neither is consumed or created.
Convergence between these plates has resulted in the formation of the Andes Mountains (the second highest mountain range on Earth), extensive volcanism, and widespread earthquake activity.
www.mhhe.com /earthsci/geology/mcconnell/plate_tectonics/cpb.htm   (719 words)

 Plate Tectonic Reconstructions at UTIG
PLATES maintains an up-to-date oceanic magnetic and tectonic database, continuously adding new paleomagnetic, hot spot, geological and geophysical data to extend the span and accuracy of global plate reconstructions.
PLATES' reconstructions are built around a comprehensive database of finite-difference poles of rotation, derived both from extensive plate motion research at UTIG, using the PLATES interactive plate modeling software, and from published studies.
PLATES reconstructions provide a solid framework on which to build detailed geological models, such as basin response to regional crustal motion, likely sequences of depositional paleoenvironment, or probable geothermal consequences of plate position or movement.
www.ig.utexas.edu /research/projects/plates/plates.htm   (675 words)

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