Anatomy of Earth Help (page 2)

By — McGraw-Hill Professional
Updated on Sep 16, 2011

The Interior

The Earth can be considered to have four distinct layers. The central portion, called the inner core , is believed to be solid. It is extremely hot and consists mainly of iron and nickel. These metals are ferromagnetic , meaning that they can be magnetized. Surrounding the inner core is a liquid iron and nickel layer called the outer core . This liquid flows in huge eddies that are thought to be responsible for the magnetization of the core and hence for the existence of the geomagnetic field .

Above the outer core lies the mantle , consisting of rock similar to granite (called basaltic rock ). The consistency of the mantle would appear solid if you could take a piece of it and hold it in your hand. However, on a long time scale and considered in its entirety, it is a fluid mass. As the eons pass, the mantle flows much like hot tar or molasses, rising up from the center of the planet toward the surface in some places and descending in other zones. One theory holds that this is a mechanism for the transfer of heat from the hot core regions to the surface, where the heat energy ultimately is transferred to the atmosphere and radiated into space. The up-and-down currents result in lateral movement near the upper reaches of the mantle.

The outermost layer, called the crust , floats on top of the mantle and, as the ages pass, moves around on it. The lateral movements of the mantle carry chunks of crust along. The crust is not a uniform, continuous mass but instead has regions where it is deep (about 30 km, or 20 mi) and other regions where it is shallow (perhaps as thin as 10 km, or 6 mi). The thickest parts of the crust form the continents and larger islands. The thin regions lie beneath the seas and oceans. Figure 8-3 is a simplified cross-sectional diagram of the Earth as it would appear if it were sliced in half at the equator.

An Extraterrestrial Visitor’s Analysis of
Earth Anatomy Of Earth The Interior

Figure 8-3. Simplified cross-sectional diagram of Earth.

Practice problems of this concept can be found at: The Planet Earth Practice Problems

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