Geosphere Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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The geosphere is the nonliving inorganic portion of the earth, in contrast to its thin surface layer of living things called the biosphere. The geosphere is the whole inorganic earth, including the lithosphere, the hydrosphere, and the atmosphere.

The earth is roughly spherical in shape. Most of the interior of the earth is invisible to human observations. The term geosphere is used to point to the layers of the earth as a solid globe, as if an observer could imagine a cutaway of the earth from its central interior to the outer most limits of the atmosphere. The whole planet is in dynamic motion in terms of geological time. The core is believed to be solid dense metal surrounded by the semi-molten mantle. It has unevenly heated convection currents in the molten mantle that causes movements in the earth’s crust that appear as plate tectonics on the surface.

Geologists believe that the earth’s solid metal core is probably nickel, iron, and some other heavy metals. It lies at a depth of 1,800 to 3,100 miles (2,900 to 5,000 kilometers) from the surface. Above the core is the semisolid outer core. It is intensely hot, as is the core of the earth. The layer above it is the mantle. It is molten and composed of lighter elements that crystallize near the surface, becoming a layer called the lithosphere. It floats on the surface of the mantle, like the skin of a warm bowl of vanilla pudding. The lithosphere is the crust of the earth that forms the continents. It is rich in calcium, sodium, potassium, and aluminum. It has a lighter mass than the mantle or the crust of the ocean floor, which is chemically closer to the chemistry of the mantle, but with more silicon. Between the lithosphere and the mantle is the asthenosphere. It is about 110 miles (180 kilometers) thick. It is composed of the plates upon which the lithosphere rides over the mantle.

Both the ocean floor and the continents are covered by the regolith, which is a covering of rock much like a blanket. The soils of the earth are either formed by the regolith or by sedimentation. Regolithic erosion occurs when solid rocks rot due to chemicals, water, or wind. The biosphere is the thin layer of living plants and animals that cover the surface of the earth, and to a lesser degree the upper levels of the oceans.

The hydrosphere is the water blanket that covers much of the surface of the earth. This water blanket contains life, and is necessary for life, but it is not in itself alive. Some of the hydrosphere consists of the lakes, rivers, ponds, and other bodies of water found on the surface of the earth. The atmosphere as part of the geosphere is composed of gases, dust, and other particles, including floating mold spores and viruses. The atmosphere is also necessary for life.

Some natural scientists use the term geosphere in a restricted sense that is synonymous with lithosphere. Others use it to refer only to the solid earth-the core, the mantle, and the crust. Both of these definitions exclude the atmosphere and the hydrosphere as part of the geosphere. During the evolution of the earth, the geosphere has interacted in a variety of ways with the biosphere, as have the atmosphere, the lithosphere, and the hydrosphere. Of significance to natural scientists are the many ways these interactions of the geosphere-biosphere have happened. Geosphere interactions include the precipitation of minerals from superheated water moving toward the surface of the earth. The creation of life forms or geographical features is part of the interactions of the geosphere and the biosphere. Other interactions include how the hydrosphere has eroded the lithosphere to create sedimentary layers, or the interactions of water to change the chemistry of the lithosphere.

Bibliography:

W.G. Ernst, Earth Systems: Processes and Issues (Cambridge University Press, 2000);
National Research Council, Satellite Gravity and the Geosphere: Contributions to the Study of the Solid Earth and Its Fluid Envelopes (National Academies Press, 1997);
Jurgen Schultz, Ecozones of the World: The Ecological Division of the Geosphere (Springer-Verlag, 1995).