Friday, December 30, 2011


From the standpoint of Physical Geography, the Earth can be seen to be composed of four principal components:

Lithosphere - describes the solid inorganic portion of the Earth (composed of rocks, minerals and elements). It can be regarded as the outer surface and interior of the solid Earth. On the surface of the Earth, the lithosphere is composed of three main types of rocks:

  • Igneous - rocks formed by solidification of molten magma.
  • Sedimentary - rocks formed by the alteration and compression of old rock debris or organic sediments.
  • Metamorphic - rocks formed by alteration of existing rocks by intense heat or pressure.

Atmosphere - is the vast gaseous envelope of air that surrounds the Earth. Its boundaries are not easily defined. The atmosphere contains a complex system of gases and suspended particles that behave in many ways like fluids. Many of its constituents are derived from the Earth by way of chemical and biochemical reactions.

Hydrosphere - describes the waters of the Earth. Water exists on the Earth in various stores, including the atmosphere, oceans, lakes, rivers, soils, glaciers, and groundwater. Water moves from one store to another by way of evaporation, condensation, runoff, precipitation, infiltration and groundwater flow.

Biosphere - consists of all living things, plant and animal. This zone is characterized by life in profusion, diversity, and ingenious complexity. Cycling of matter in this sphere involves not only metabolic reactions in organisms, but also many abiotic chemical reactions.

All of these spheres are interrelated to each other by dynamic interactions, like biogeochemical cycling, that move and exchange both matter and energy between the four components.

Pidwirny, M. (2006). "The Natural Spheres". Fundamentals of Physical Geography, 2nd Edition. 30/11/2011.

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