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  Encyclopedia of Keywords > Mid-Ocean Ridges > Oceanic Lithosphere   Michael Charnine

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  1. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years, but after this becomes increasingly denser than asthenosphere.
  2. Oceanic lithosphere is typically about 50-100 km thick (but beneath the mid-ocean ridges is no thicker than the crust).
  3. Oceanic lithosphere is generally not denser than asthenosphere but continental lithosphere is lighter.
  4. Oceanic lithosphere is destroyed at subduction zones where lithosphere descends into the mantle beneath trenches.
  5. As oceanic lithosphere is formed at spreading ridges from hot mantle material it gradually cools and thickens with age (and thus distance from the ridge).

Older Lithosphere

  1. In short, new oceanic lithosphere was created at the mid-ocen ridges and pushed older lithosphere.

Heavier Oceanic Lithosphere

  1. When this occurs, the heavier oceanic lithosphere sinks beneath the continental plate.

Subducting Oceanic Lithosphere

  1. The Sangihe trench was active at that time, subducting oceanic lithosphere of the Molucca Sea to the west.

Old Oceanic Lithosphere

  1. Thus old oceanic lithosphere will sink into the asthenosphere if it gets the chance.


  1. Thus, old oceanic lithosphere may have significant strength to depths in excess of 60 km or about half that of the thermal lithosphere.


  1. Nevertheless, it is often possible to look through the deformation and alteration and learn something about the structure of oceanic lithosphere.


  1. It suggests that the continents are less strong and less rigid than oceanic lithosphere.


  1. Diffuse plate boundaries, which are zones of deformation hundreds to thousands of kilometres wide, occur in both continental and oceanic lithosphere.


  1. D ivergence, and the creation of new oceanic lithosphere, can go on for tens or hundreds of millions of years.


  1. Oceanic lithosphere ranges from 50 km to 100 km in thickness, and continental lithosphere ranges from 40 km to 200 km.
  2. The thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time.


  1. Sea floor topography is controlled by the age of the oceanic lithosphere and the rate of spreading.


  1. This is the place where new oceanic lithosphere is made and how fast this is happening effects the topography of the ridge.


  1. Average oceanic lithosphere is typically 100 km thick[ 5]; its thickness is a function of its age: as time passes, it conductively cools and becomes thicker.


  1. Gabbro is also part of the oceanic lithosphere (ophiolite suite) forming as a thick layer below the top-most pillow lavas across all the oceanic floors.
  2. Earthquakes occur in the cold, brittle upper part of the oceanic lithosphere as it is subducted.


  1. A plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere.


  1. Only in a few places, mainly Iceland and the Afar region in northeastern Africa, rifting, which generates oceanic lithosphere, is occurring on land.

Square Meter

  1. Trenches form where oceanic lithosphere is subducted at a convergent plate margin, presently at a global rate of about a tenth of a square meter per second.


  1. The Molucca Sea is the only present day example of ocean basin closure as a result of subduction of oceanic lithosphere in two opposite directions.
  2. The net effect is that subduction efficiently removes old oceanic lithosphere.

Oceanic Ridges

  1. And, ridges in the deep oceans that rise above the abyssal plains and where new oceanic lithosphere is created are called oceanic ridges.

Oceanic Crust

  1. New oceanic lithosphere, or at least the oceanic crust, is formed at constructive plate boundaries.


  1. Evolution of oceanic lithosphere: A driving force study of the Nazca plate.

Continental Lithosphere

  1. When oceanic lithosphere collides with continental lithosphere, the oceanic plate will descend into the subduction zone (Fig.
  2. Plates with continental lithosphere have lower relative velocities than plates with only oceanic lithosphere.
  3. When oceanic lithosphere collides with continental lithosphere, it subducts beneath the continental lithosphere.


  1. During plate collision and subduction, terranes may be scraped off the oceanic lithosphere and become part of the continent.


  1. The fractionation and solidification of these magmas form the ophiolite suite, the four layers of rock that form the oceanic lithosphere.
  2. Rifting is said to have enter an intermediate phase once new oceanic lithosphere begins to form through the creation of a new midocean ridge.
  3. New oceanic lithosphere forms through volcanism in the form of fissures at mid-ocean ridges which are cracks that encircle the globe.


  1. Oceanic lithosphere disappears into trenches at a global rate of about a tenth of a square meter per second.
  2. Oceanic lithosphere moves into trenches at a global rate of about a tenth of a square metre per second.


  1. Continental Volcanic Arc Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent.
  2. Subduction of the oceanic lithosphere beneath the continental lithosphere produces continental volcanic arcs that erupt mostly andesitic magma.
  3. One slab of oceanic lithosphere is pushed beneath another in a process called subduction.


  1. Thick, cold, dense oceanic lithosphere sinks at subduction zones, pulling the rest of the ocean plate.
  2. Slab-pull occurs where cold, dense oceanic lithosphere is subducted and pulls the trailing lithosphere along.
  3. In places where plate accretion has occurred, land masses may contain the dense, basaltic rocks that are usually indicative of oceanic lithosphere.


  1. Slab pull When the denser, heavier oceanic lithosphere sinks and pulls the rest of the tectonic plate with it.


  1. The plate represents oceanic lithosphere that lies beneath the Philippine Sea.
  2. Stein, C. and S. Stein, Comparison of plate and asthenospheric flow models for the evolution of oceanic lithosphere, Geophys.
  3. When ocean lithosphere runs into a plate with continental lithosphere, the oceanic lithosphere is subducted beneath the continental lithosphere.


  1. When two plates of oceanic lithosphere run into one another the subducting plate is pushed to depths where it causes melting to occur.
  2. Further west is the Juan de Fuca Ridge, where two plates of the oceanic lithosphere are spreading apart.
  3. The upper parts of the plates carry water in fractures, seafloor sediments, and the altered minerals of the oceanic lithosphere itself.

Ocean Basins

  1. Because oceanic lithosphere may get subducted, the age of the ocean basins is relatively young.


  1. Ophiolites occur in areas where obduction (the opposite of subduction) has pushed a section of oceanic lithosphere onto continental crust.
  2. Nevertheless, we have a fairly good understanding of the structure of the oceanic lithosphere from seismic studies and ophiolites.


  1. In addition, deep trenches that occur along zones where oceanic lithosphere descends back into the mantle are called oceanic trenches.
  2. Because oceanic lithosphere is cold and brittle, it fractures as it descends back into the mantle.
  3. At this point, the density of the oceanic lithosphere increases and it is carried into the mantle by the downwelling convective currents.


  1. Plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere.
  2. The density of oceanic lithosphere is similar to that of the asthenosphere, and it can thus fairly easily be pushed down into the uppermost mantle.
  3. As oceanic lithosphere moves away from the ridge, it cools and sinks deeper into the asthenosphere.


  1. Of the two plates, the one to be subducted is the plate with oceanic lithosphere.
  2. Oceanic subduction boundaries are those at which oceanic lithosphere is thrust (subducted) beneath either continental or oceanic lithosphere.
  3. Trenches form where oceanic lithosphere is subducted at a convergent plate margin, presently at a global rate of about a tenth of a square metre per second.


  1. Types The lithosphere is divided into two categories: the continental lithosphere and the oceanic lithosphere.

Subduction Zone

  1. The older of the two plates descends into the subduction zone when plates of oceanic lithosphere collide along a trench.
  2. Figure 8–11 shows magma forming in a subduction zone, where oceanic lithosphere is sinking beneath a continent.
  3. Water is driven out of the oceanic lithosphere in subduction zone s, and it causes melting in the overlying mantle.

Subduction Zones

  1. Interactions along convergent boundaries involve the collision of pairs of plates where oceanic lithosphere is often destroyed at subduction zones.
  2. The production of oceanic lithosphere at these ridges was accommodated through its destruction at subduction zones.
  3. Water is driven out of the oceanic lithosphere in subduction zones, and it causes melting in the overlying mantle.

Mid-Ocean Ridge

  1. Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge.

Mid-Ocean Ridges

  1. Plates move apart, or diverge, at mid-ocean ridges where seafloor spreading forms new oceanic lithosphere.
  2. New oceanic lithosphere capped by basaltic crust is created at the mid-ocean ridges, and this newly formed plate moves away from the ridges.
  3. Back-arc spreading centres are similar to mid-ocean ridges, and produce new oceanic lithosphere in back-arc basins by sea-floor spreading.

Oceanic Lithosphere

  1. Crust is always less dense than asthenosphere or lithospheric mantle and continental lithosphere is always less dense than oceanic lithosphere.
  2. Oceanic Lithosphere The rigid, outermost layer of the Earth comprising the crust and upper mantle is called the lithosphere.
  3. Subduction zones exist at convergent plate boundaries where one plate of oceanic lithosphere converges with another plate and sinks below into the mantle.


  1. Mid-Ocean Ridges
  2. Subduction Zones
  3. Places > Earth > Geology > Lithosphere
  4. Subducted
  5. Events > Earthquakes > Plate Tectonics > Asthenosphere
  6. Books about "Oceanic Lithosphere" in

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  Originally created: April 04, 2011.
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