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Internal Structure and composition of the Earth

Current technology only enables us to drill a few kilometers into the ground, which depth is hardly sufficient for us the obtain any concrete evidence of the subterranean composition of the Earth.

However, by studying the composition of volcanic material and patterns of seismic waves through different types of material, Geophysicists have come to the logical conclusion that the Earth consists of 3 main layers, the crust, the mantle and the core.


Earth and atmosphere cutaway illustration.
Source: Wikipedia, the free encyclopedia.

The Crust

The crust is the outermost layer, and consists of the continental crust and oceanic crusts.

The oceanic crust is denser than the continental crust, having an average density of 3g/cm3, compared to 2.7g/cm3 of the continental crust. The oceanic crust is generally thinner, averaging 5km to 10km thick, while the continental crust can be as thick as 90km under the Himalayas.

The Mantle

The mantle extends from the bottom of the crust to a depth of 2900km. The density of rocks and temperature generally increase with depth, where densities may reach 5.5g/cm3 near the crust and temperatures exceed 2000 degrees celsius.

The mantle consists of the upper and lower mantle, and the upper mantle is further subdivided into 3 layers. Some seismologists believe that convection currents, which result in the plate movement, occur in the semi-molten asthenosphere layer in the upper mantle.

The Core

The core is the innermost layer of the Earth. It consists of very dense rock which may exceed 15g/cm3.

The temperatures here are extremely high, probably between 4000 and 5000 degrees celsius. Under immense pressure, the inner core is solid, while the outer core is semi-molten, being under less pressure.

References

  • Retrieved February 1, 2005, from http://pubs.usgs.gov/publications/text/historical.htm
  • Elastic Rebound. Pacific Earthquake Engineering Research Center. Retrieved March 5, 2005, from http://peer.berkeley.edu/~jrodgers/EQDef/eqdef2.htm
  • 2004 Indian Ocean earthquake. Wikipedia. Retrieved February 20, 2005, from http://en.wikipedia.org/wiki/2004_Indian_Ocean_Earthquake
  • Tsunami. Wikipedia. Retrieved February 20, 2005 from http://en.wikipedia.org/wiki/Tsunami
  • The Earth: A Living Planet Retrieved April 10, 2005, from http://www.seed.slb.com/en/scictr/watch/living_planet/beneath.htm
  • Marianne Chong. Aspects of Physical Geography (2001).
  • Plate Tectonics. Wikipedia . Retrieved April 10, 2005, from http://en.wikipedia.org/wiki/Plate_tectonics

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