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Narrative Description of Earth Anatomy Poster
(Detailed descriptions of these layers can be obtained in most Geology or Earth Science textbooks.)
The earth's inner-core is a contained sphere about 5000 km deep within the earth. Even though the temperature of the inner- core is estimated to be as hot as the surface as the Sun (~6000 Celsius degrees), the enormous pressures keep the core in a solid state (The over-laying layers of earth cause pressures in excess of 3 to 4 million atmospheres). This solid spherical core is believed to consist primarily of iron and nickel.
The outer-core, like the inner-core, is also composed primarily of iron and nickel, but unlike the inner-core, this portion of the earth is thought to be a shell of liquid metal. The fluid motions of this metallic region are theorized to be the origin of the earth's magnetic field.
The next layer is the mantle and is approximately 2900 km thick.
This extends from the top of the
Inner-core to the Mohorovicic discontinuity (also known as the Moho or crust-mantle boundary) . This region,
composed of hot dense rock, constitutes the majority of the earth's
volume. The main components of this rock in order of abundance are:
silicon, oxygen, iron, and magnesium.
The section closest to the core is the lower mantle. The interface between the core and the mantle is as pronounced as the earth's surface and it's atmosphere. Rock at this depth is under substantial pressure and is relatively solid (30 to 100 times the viscosity of the upper-mantle).
Above the lower mantle is the upper mantle . The pressure and heat in this zone allows rock to flow in what's known as a plastic manner. The rising and cooling of hot mobile molten rock is believed to occur in this layer. This method of heat dissipation is called convection and is considered one of the possible driving forces of plate tectonics .
At the top of the upper mantle is an important layer known as the asthenosphere, an area of viscous rock that enables the lithospheric plates above to slide around.
Riding over the top of the asthenosphere, is the lithosphere. This thin layer, relatively speaking, consists of huge plates that migrate over the surface of the globe. The lower portion of this layer, though solid is still considered part of the mantle. Firmly joined above to this lower portion of plate, is the layer we live on, the crust.- The crust is the thinnest, most buoyant and brittle of all the layers. Even though scientists can't see the separation between these two connected layers, they know it exists because of changes in seismic velocities due to density. This seismic boundary is known as the Mohorovicic discontinuity.
As you progress further outward, you finally reach the surface of the crust. This surface is the earth's interface with sky, water, life and light.
Wright Fellow Eric Muller was mainly responsible for executing this poster; Dana Berry did the artwork.