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Topic: Sea floor spreading

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In the News (Thu 18 Jul 19)

  Sea-Floor Spreading   (Site not responding. Last check: 2007-10-31)
Sea-floor spreading is the process in which the ocean floor is extended when two plates move apart.
The boundaries where the plates move apart are 'constructive' because new crust is being formed and added to the ocean floor.
On the whole, sea-floor spreading is basically volcanic, but it is a slow and regular process, without the explosive outbursts of the volcanoes on land.
library.thinkquest.org /17457/platetectonics/4.php   (265 words)

 Columbia Encyclopedia- seafloor spreading - AOL Research & Learn
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.
First, samples of the deep ocean floor show that basaltic oceanic crust and overlying sediment become progressively younger as the mid-ocean ridge is approached, and the sediment cover is thinner near the ridge.
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.
reference.aol.com /columbia/_a/seafloor-spreading/20051207050809990014   (590 words)

 Sea Floor Spreading   (Site not responding. Last check: 2007-10-31)
New oceanic crust is created at the crest of the ridge, and as the crust ages, it moves outward and downward toward the flanks of the ridge.
Start spreading once again and let it continue until it stops at 0 M.Y. The rhombic region containing diagonal stripes is the zone traversed and sheared by the migrating transform fault.
Before the concept of sea-floor spreading was accepted by most geoscientists, the only class of faults with horizontal displacement that was recognized was the transverse fault.
visearth.ucsd.edu /VisE_teach/lessons/Sea_floor_act.html   (1437 words)

 Plate tectonics and sea-floor spreading - an alternative view   (Site not responding. Last check: 2007-10-31)
Ductile flow and underplating - spreading and thinning of the outer 'skin' of the mantle as it rises into the gaps, and crystallisation of the underlying layer on to the thinned outer shell to maintain crustal thickness.
Ductile spreading occurs as shown diagrammatically by the lineated elements and at the interfaces of mantle 'layers' (compare).
The spread elements of the faults form the scarp slopes of the abyssal hills as each successive underplated mantle layer element is exhumed.
users.indigo.net.au /don/ee/spreading.html   (578 words)

 SEA — — Academics — K-12
Sea floor spreading is the process in which the ocean floor on each side of a rift valley is pushed away by lava erupting from the mantle beneath the Earth's crust.
The old ocean floor is pushed away from the rift valley on both sides.
Describe the pattern you observed on the sea floor.
www.sea.edu /academics/k12.asp?plan=midoceanmagnetism   (546 words)

 Sea-Floor Spreading and Subduction Model
Slide the sea floor into the three slits in the shoebox and pull it down from underneath so that the numbers "4" are just visible.
Now move the sea floor back to the 4 my before present position, and this time, while the sea floor is moving, watch the boundaries where slip is occurring.
From the ages of the sea floor and the scale of the model, which is the same in the vertical and horizontal directions, one can determine that the plate in this model is being subducted at a rate of about 50 km/my.
pubs.usgs.gov /of/1999/ofr-99-0132   (1617 words)

 Introduction to Plate Tectonics   (Site not responding. Last check: 2007-10-31)
Harry Hess proposed that new ocean floor is formed at the rift of mid-ocean ridges.
The ocean floor, and the rock beneath it, are produced by magma that rises from deeper levels.
A trench is a steep-walled valley on the sea floor adjacent to a continental margin.
volcano.und.nodak.edu /vwdocs/vwlessons/plate_tectonics/part8.html   (247 words)

 Class Notes: Con Drift, Sea Floor Spreading
hile examining the sea floor, especially the sediment composition and thickness, it was recognized in the 60s that the sea floor did not have a uniform sediment thickness.
ecause the sea floor at the ridge axis is new (like this year's new Ford car or truck), there was little or no time for sediment particles to accumulate or to become thick.
Spreading centers of this movement are found at the axis of mid-ocean ridges.
duedall.fit.edu /ocn1010eng/jan21.htm   (1603 words)

 Caribbean VR
New ocean floor is produced at the mid-ocean ridge by a process called "sea floor spreading".
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)

 Plates: sea-floor spreading
Sea-floor spreading is the mechanism by which new crust of the Earth is created and the continents move.
As new oceanic crust is formed at the spreading ridges, to either side the crust moves gradually away.
Sea-floor spreading therefore provides a mechanism for the movement of the continents, proof that they are moving, and by studying the age distribution of the basalts, a record of the rates of movement in the geological past.
www.shu.ac.uk /services/ssc/participation/tasters/jigsaw/plsfs.htm   (455 words)

 North Atlantic sea-floor spreading rates: Implications for the Tertiary development of inversion structures of the ...
The correct identification of magnetic anomalies and their ages and the analysis of spreading rates during the formation of this ocean are important in understanding the development of the region and specifically the history of its passive margins.
Spreading rates generally slowed down from 2 cm a^sup -1^after Early Eocene initiation of sea-floor spreading, to values around 0.5 cm a^sup -1^ in Oligocene time.
An increase in spreading rates to around 1 cma ^sup -1^ coincided with the positioning of the Iceland hotspot under the North Atlantic mid-ocean ridge.
www.findarticles.com /p/articles/mi_qa3721/is_200209/ai_n9141129   (897 words)

 Plate Tectonics - Discover Our Earth
Additionally, the age distribution of the ocean floor is symmetrical along the axis of the ridge.
The youngest rocks on the floor of the Atlantic are at the mid ocean ridge.
Because the reversal pattern is irregular, but the same all over the world, it can be used like tree rings to date rocks by examining the pattern of magnetization that they preserve.
atlas.geo.cornell.edu /education/student/tectonics/sea_floor_spreading_i.html   (358 words)

 Plate Motions - Clues from the Sea Floor
Much of the evidence leading to Plate Tectonic Theory came from defense-related mapping of the sea floor in the 1940’s and 1950’s.
Before then, almost nothing was known about the rocks of the ocean floor, and there was little reason to suspect that the geology of the ocean floor was much different from that of the continents.
Another surprise was the spatial pattern in the ages of the ocean floor rocks.
daphne.palomar.edu /lyon/Assignments/seafloorclues.htm   (690 words)

 Untitled   (Site not responding. Last check: 2007-10-31)
Seafloor spreading - The seafloor is characterized by mid-ocean ridges.
New, young sea floor is continually being formed by basalt eruptions at the ridge crest.
The magnetic reversals near the mid-ocean ridges allows the prediction of the age of the sea floor and the rate of the sea-floor motion.
www.geosc.psu.edu /~engelder/geosc20/lect26.html   (586 words)

 Introduction to Plate Tectonics   (Site not responding. Last check: 2007-10-31)
The volcanic rocks which make up the sea floor have magnetization because, as they cool, magnetic minerals within the rock align to the Earth's magnetic field.
Vine and Matthews proposed that lava erupted on the sea floor on both sides of the rift, solidified, and moved away before more lava was erupted.
The ability of Vine and Matthews' hypothesis to explain the observed pattern of ocean floor magnetic anomalies provided strong support for sea floor spreading.
volcano.und.nodak.edu /vwdocs/vwlessons/plate_tectonics/part9.html   (420 words)

 Plate tectonics and sea floor spreading, Oceanography 1010, 16 January 2001
hen people first started examining the detail of the sea floor, especially the sediment composition and thickness, they recognized that the sea floor was not uniform with respect to sediment thickness.
ecause the sea floor at an ocean ridge axis is new (like this year's new Ford car or truck, or a Chevy if you are in to GMC products), there was little or no time for sediment particles to accumulate to become thick mat of material.
These reversals provide a pattern in rock demonstrating the direction of sea floor spreading and is used to explain continental drift.
duedall.fit.edu /ocn1010eng/week2-1.htm   (2210 words)

 Sea floor spreading - boudinage analogue   (Site not responding. Last check: 2007-10-31)
And that's all there is to it, basically,...uplift of the mantle to keep filling the axial gap as the fractured segments of crust move apart on the enlarging substrate.
Whilst dykes may intrude the ocean floors dyke intrusion is assuredly not the main mechanism of sea-floor spreading.
Conceptually, it is neither clear what the dykes are supposed to be intruding, nor what they are supposed to be feeding in a fracture which is circumglobal, segmented by transform faults, purported to exhibit the same age of dyke intrusion for its entire length, and yet never shows any evidence of dykes cross-cutting transform faults.
users.indigo.net.au /don/cpr/boudalogue.html   (730 words)

 New Hypothesis Provides A Basis For The Reality Of The Legendary Continents Of Atlantis And Lemuria   (Site not responding. Last check: 2007-10-31)
Although sea-floor spreading will still have a small place in geoscientists’ understanding of certain aspects of the origin and maintenance of continents and ocean basins, the really big picture, of elevation of ocean floors and - to a lesser degree - continents will rest upon a model that is driven by mantle surges.
The continents may either be carried along by the adjacent sea floor, or the spreading sea floor may under-thrust a relatively immovable continent.
Further questions are related to the concept of ocean floor spreading and the tape-recorder model for generating the oceanic magnetic stripes.
www.bibliotecapleyades.net /atlantida_mu/esp_lemuria_6.htm   (5024 words)

In the eastern Mediterranean-Black Sea area, the limits of the Proto-Tethys Ocean during the latest Carboniferous, and consequently the outlines of the Hercynian fold belt as shown in the Permo-Carboniferous reconstruction given by Plate 6, are conceptual.
This is exemplified by the Oligocene abandonment of the Labrador-Baffin Bay and the Aegir spreading axes in favor of the Reykjanes-Kolbeinsey-Mohn's spreading axis.
Ultimate abandonment of the Labrador Sea-Baffin Bay spreading axis, and late Oligocene stabilization of spreading axes in the Norwegian-Greenland Sea to the Kolbeinsey Ridge, also suggests that the Labrador Sea spreading system and the Aegir Ridge were not superimposed on a permanent, deep asthenospheric upwelling cell.
www.searchanddiscovery.com /documents/97020/memoir43.htm   (13414 words)

 When the Earth Moves - Summary
measurements to map the ocean floor leading to the discovery of a large undersea mountain ranges with midocean ridges.
To explain the ridges, Henry Hess theorized that the seafloor was slowly spreading away from the ridges, driven by convection currents in the mantle (see Insights from the Ocean).
Confirmation of Hess's theory of seafloor spreading came from a magnetic survey of the material on either side of a midocean ridge (see Of Magnetism and Time).
www.beyonddiscovery.org /content/view.article.asp?a=229   (374 words)

 sea-floor spreading
Sea-floor spreading occurs where oceanic plates are diverging from one another.
As a result, the age of the rocks increases as one moves away from the rift zone.
Earthquakes and volcanoes are where sea floor spreading is occurring.
www.uwsp.edu /geo/faculty/ritter/glossary/s_u/sea_flr_spread.html   (75 words)

 The Earth -- Introduction
Echo sounders are used to measure the depth to the sea floor.
This energy penetrates the rocks beneath the sea floor and are analyzed in the same way that seismologists analyze naturally occurring Earthquakes.
As the oceanic crust ages and begins to spread laterally the deep sea sediment layer thickens.
www.uh.edu /~jbutler/physical/chapter17notes.html   (809 words)

 Plate Tectonics
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.
The unusual thing about the area under study is a large mountain, called the Atlantis Massif, just west of the Mid-Atlantic spreading center at 30°N. The peak of the mountain is 1,700 m (5,000') higher than the usual spreading ridge crest.
www.platetectonics.com /article.asp?a=95&c=4   (944 words)

 Untitled Document   (Site not responding. Last check: 2007-10-31)
Background: Marine magnetic anomalies provide a "tape recorder" of sea floor spreading that can be used to map out the details of motion.
Measure the distance from the ridge to all the identifiable magnetic anomalies on the profile (with a ruler).
Provide a brief summary of the spreading episode, including: age of initiation, periods of fast or slow spreading, symmetric or asymmteric spreading across the ridge and any other details you can squeeze out of the data.
www.mines.utah.edu /~dchapman/gg506/GG506LAB_SeaSpreading.html   (125 words)

 Seafloor Spreading
It shows the ages of ocean floor in the Atlantic and eastern Pacific Oceans.
As new seafloor forms at the spreading ridges, older parts move away from the ridge.
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)

 North Cascades Geology: Sea-Floor Spreading
Comparing magnetic stripes on the sea floor to the magnetic reversals in basalt on the land as seen in a vertical cliff.
Furthermore, the oldest stripes were farthest from the ridges, suggesting that the floor was growing and spreading by addition of material at the ridges.
Besides where the plates spread apart, where new lithosphere is made, and subduction zones, where lithosphere is destroyed, there are boundaries, world-class faults where lithospheric plates slide past one another.
www2.nature.nps.gov /geology/USGSNPS/noca/nocageol4c.html   (787 words)

 NOVA Online | Into the Abyss | Birth of an Expedition
They were looking for hydrothermal vents, cracks in the seafloor where seawater that has seeped into the ocean floor and come into contact with superheated rock rushes back up at scalding temperatures.
The scientists found the vents, lending support to the notions of seafloor spreading, plate tectonics, and continental drift.
These oases in the deep sea (see Living at Extremes) led some scientists to wonder whether life itself might have begun at hydrothermal vents, or at least in an environment much like it.
www.pbs.org /wgbh/nova/abyss/mission/birth.html   (685 words)

 Catastrophist Tectonics
Here I argue that the evidence overwhelmingly supports the accuracy of the spreading rate histories derived from the geomagnetic polarity time scale, and that the catastrophist explanations of sea-floor spreading are 'catastrophically' at odds with the geologic evidence.
This implies that the average rate of spreading on the side of the ridge axis was about 100mm/yr, and that the rate of spreading remained steady over millions of years.
Many additional spreading rates of this kind were subsequently computed, and used to construct detailed models of plate motions over time.
www.geocities.com /earthhistory/CT.htm   (2160 words)

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