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Earth’s Interior | National Geographic

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Inside the Earth

The Earth’s interior is composed of four layers, three solid and one liquid—not magma but molten metal, nearly as hot as the surface of the sun.

The deepest layer is a solid iron ball, about 1,500 miles (2,400 kilometers) in diameter. Although this inner core is white hot, the pressure is so high the iron cannot melt.

The iron isn’t pure—scientists believe it contains sulfur and nickel, plus smaller amounts of other elements. Estimates of its temperature vary, but it is probably somewhere between 9,000 and 13,000 degrees Fahrenheit (5,000 and 7,000 degrees Celsius).

Above the inner core is the outer core, a shell of liquid iron. This layer is cooler but still very hot, perhaps 7,200 to 9,000 degrees Fahrenheit (4,000 to 5,000 degrees Celsius). It too is composed mostly of iron, plus substantial amounts of sulfur and nickel. It creates the Earth’s magnetic field and

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Earth’s Interior & Plate Tectonics

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Earth’s Interior & Plate Tectonics

Copyright © 1995-2009 by Rosanna L. Hamilton.
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A theory is a tool – not a creed. -J. J. Thomson

The Earth’s Interior

Just as a child may shake an unopened present in an attempt to
discover the contents of a gift, so man must listen to the ring and
vibration of our Earth
in an attempt to discover its
content. This is accomplished through seismology, which has
become the principle method used in studying Earth’s interior.
Seismos is a Greek word meaning shock; akin to earthquake,
shake, or violently moved. Seismology on Earth deals with the
study of vibrations that are produced by earthquakes, the impact
of meteorites, or artificial means
such as an explosion. On these
occasions, a seismograph is used to measure and record the
actual movements and vibrations within the Earth and of

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