In Aristotelian physics, the term was applied to four spherical natural places, concentrically nested around the center of the Earth, as described in the lectures Physica and Meteorologica. They were believed to explain the motions of the four terrestrial elements: Earth, Water, Air and Fire.
In modern texts and in Earth system science, geosphere refers to the solid parts of the Earth and is used along with atmosphere, hydrosphere, and biosphere to describe the systems of the Earth (the interaction of these systems with the heliosphere is sometimes listed). In that context, sometimes the term lithosphere is used instead of geosphere. However, the lithosphere only refers to the uppermost layers of the solid Earth (oceanic and continental crustal rocks and uppermost mantle).
Since space exploration began, it has been observed that the extent of the ionosphere or plasmasphere is highly variable, and often much larger than previously appreciated, at times extending to the boundaries of the Earth's magnetosphere or geomagnetosphere. This highly variable outer boundary of geogenic matter has been referred to as the "geopause," to suggest the relative scarcity of such matter beyond it, where the solar wind dominates.
- Skinner, B: "The Dynamic Earth.", page 21. John Wiley & Sons, Inc, 2000 ISBN 0-471-16118-7
- Allaby,A. and Allaby, M. (eds). 2003. The Dictionary of Earth Sciences. Oxford University Press. Oxford University Press Inc., New York. 2nd edition. pg. 320.
- Siscoe, G.: Aristotle on the Magnetosphere, Eos Transactions of Am. Geophys. Un., v.72, pp. 69-70, 1991.
- Moore, T.E. and D.C. Delcourt, The Geopause, Revs. Geophys., v32(2), p.175, 1995.
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