lunes, 2 de enero de 2012

Layers of the Earth



Crust -The outer layer of the Earth. The crust consists of ocean plates and continental plates. The crust is composed of light material called rock. The crust and the outer layer of the mantle together are called the lithosphere. The lithosphere is very brittle and light and moves because of convection currents in the lower layer of the mantle called the asthenosphere.

Oceanic Crust -Made of dense basaltic rock. Oceanic plates carry the continental plates across the surface of the Earth.

Continental Crust -Made of light granitic rock. Continental crust rides on the oceanic crust.

Lithosphere - The crust and the upper rigid layer of the mantle seem to move together and form the plates of the Earth.

Mantle -Largest layer of the Earth located directly under the crust. The mantle is composed of very hot, dense, flowing rock. The material in the mantle flows because of convection currents.

Asthenosphere - Lower layer of the mantle. This is the layer that flows and moves the plates of the Earth. Flows very slowly with the consistency of hot asphalt under pressure.

Convection Currents - are a circular current caused by the difference in temperatures from the bottom to the top of the mantle. It is because of these currents that the plates of the Earth have moved in the past and are moving today. These plate movements cause earthquakes, mountain building, and volcanism.

Outer Core -The layer located directly under the mantle. The outer core is composed of liquid nickel and iron. Scientists believe that the outer core is liquid because S waves from an earthquake bounce of the layer instead of passing through it.

Inner Core
-The inner core is composed of nickel and iron under such great temperatures and pressures that the metals are in a solid state of motion.



Exercises:

1. Draw a diagram of the Earth’s layers and label the crust, mantle, outer and inner core




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