Layers of the Earth
Describe the properties and composition of the following major layers of
the earth:
crust
mantle
core **
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Composition of
Each Layer
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The crust is the outer layer of the Earth that
we see. It is very thin compared to the next
two layers. It is nearly 40 km (25 miles) thick
under the continents. It is much thinner under
the oceans, averaging around 7 km (4 miles)
thick. It is thickest under mountain ranges,
where it is nearly 80 km (50 miles) thick.
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The Mantle is the metal-rich zone of rock
extending from the core to the crust. It is a
dense rock that is believed to behave similar to
a child's craft putty. It moves slowly in great
circular patterns called convection cells.
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Extending about halfway to the surface from
the center is the iron rich core. Nickel is
another important element, so much so, that it
is oftentimes called a nickel-iron core.
The heat is so great that the core is liquid.
However, the pressures are so great near the
center of the earth that the iron-nickel core
changes phase from a liquid to a solid.
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** AZ Stds, Science 7, Strand 6, Concept 1, PO 2
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Updated: 3/17/07
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