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This Review contains major "Asthenosphere"- related terms, short phrases and links grouped together in the form of Encyclopedia article.
- The asthenosphere is a part of the upper mantle that exhibits plastic properties.
- Asthenosphere: The hot, slowly flowing layer of upper mantle below the lithosphere (700 km thick).
- Asthenosphere - A zone in the upper mantle of the Earth, consisting of hot, plastic rock, that underlies the stronger lithosphere.
- The asthenosphere is a layer of solid rock that is near its melting point.
- Asthenosphere is a "weak" region beneath the lithosphere.
- The lithosphere essentially floats on the asthenosphere and is broken up into what are called tectonic plates.
- The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which "float" on the fluid-like asthenosphere.
- The relative fluidity of the asthenosphere allows the tectonic plates to undergo motion in different directions.
- Due to convective currents in the asthenosphere, the tectonic plates undergo motion in different directions.
- Plate boundaries As the rock of the asthenosphere moves in different directions, it carries the plates of the lithosphere along with it.
- In the theory of plate tectonics the outermost part of the Earth 's interior is made up of two layers, the outer lithosphere and the inner asthenosphere.
- The lithosphere is cooler and more rigid, whilst the asthenosphere is hotter and mechanically weaker.
- Below the lithosphere lies the asthenosphere.
- Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere.
- This bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere.
- The deeper mantle below the asthenosphere is more rigid again.
- In the mantle layer called the asthenosphere, mantle rock melts to make magma.
- Within the crust and upper mantle there is also an inferred mechanical layering distinguishing lithosphere, asthenosphere and mesosphere.
- The upper mantle which underlies the lithosphere to a depth of 200 km is the asthenosphere.
- The molten magma, typically of basaltic composition, rises up through the asthenosphere, the mantle portion of the lithosphere, and into the lower crust.
- Geologists later discovered that radioactive decay provided a heat source within Earth's interior that made the asthenosphere plasticine (semi-solid).
- Also, the lithosphere loses heat by conduction whereas asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient.
- The lithospheric plates ride on the asthenosphere.
- Lithospheric plates on the scales of continents and oceans move at rates of centimeters per year in response to movement in the asthenosphere.
- They may originate within the asthenosphere or even deeper within the earth at the boundary between the mantle and the core.
- Ultramafic rocks with 1-10 percent magma occur in (A) the crust, (B) the lithosphere, (C) the asthenosphere, or (D) the outer core.
- The underlying, partially molten part of the mantle, on which the plates slide, is called the asthenosphere.
- Pressure on the asthenosphere may also be reduced in zones of divergence, where two plates are separating from each other.
- In this case, the lighter of the colliding plates slides upward and over the heavier of the plates, which dives down into the asthenosphere.
- Sources of plate motion As noted above, the plates are able to move because of the relative weakness of the asthenosphere.
- Others view the asthenosphere as the driving force or means of conveyance for the plates.
- Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales.
- The asthenosphere is solid even though it is at very hot temperatures of about 1600 degrees Celsius due to the high pressure from above.
- By 220km depth the asthenosphere comes to an end and the mantle goes back to a less flexible state.
- Beneath continents the asthenosphere appears at around 150km depth, while under oceans it can be as shallow as 60km.
- As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere).
- The outermost layer of the earth is called the lithosphere (100-200km deep); it is followed by a plastic asthenosphere (150-400km deep).
- This mechanism could explain the widespread range of E-W fast anisotropy presumably in the asthenosphere without a need for complicated models.
- In that case, the pressure exerted on the asthenosphere beneath it is reduced, melting begins to occur, and asthenospheric materials begin to flow upward.
- No. Eventually Earth will cool to the point that the asthenosphere will not be sufficiently ductile.
- McGeary and Plummer (1998) say that these findings cast doubt on the original, simple lithosphere-asthenosphere model of plate behavior.
- There is a suggestion that convection at the Hawaiian plume is more complicated than a parabolic pancake spread of dragged asthenosphere.
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