1. Plate tectonics is a theory of global-scale dynamics involving the movement of many rigid plates of the earth's crust. Considerable tectonic activity occurs along the margins of the plates, where buckling and grinding occur as the plates are propelled by the forces of deep-seated mantle convection currents. This has resulted in continental drift and changes in the shape and size of oceanic basins and continents.

2. Subduction zones are elongated regions along which a crustal block descends relative to another crustal block.

3. A plume is a body of magma that wells up in localized areas.

4. A fluid transport medium is a liquid that transports energy, dissolved solids, or dissolved gases from their origin to their destination.

5. D.E. White, L.J.P. Muffler, and A.H. Truesdell, "Vapor- Dominated Hydrothermal Systems Compared with Hot-Water Systems," Economic Geology, Vol. 66 (1971), pp. 75-97.

6. D.E. White and D.L. Williams, eds., Assessment of Geothermal Resources of the United Statesū1975, U.S. Geological Survey Circular 726 (1975), 155 pp.

7. W.A.J. Mahon, L.E. Klyen, and M. Rhode, "Neutral Sodium/Bicarbonate/Sulfate Hot Waters in Geothermal Systems," Chinetsu (Journal of the Japan Geothermal Energy Association), Vol. 17 (1980), pp. 11-24.

8. R.W. Henley and A.J. Ellis, "Geothermal Systems Ancient and Modern, a Geochemical Review," Earth Science Review, Vol. 19 (1983), pp. 1-50.

9. D.L. Norton, "Theory of Hydrothermal Systems," Annual Review of Earth and Planetary Science, Vol. 12 (1983), pp. 155-177.

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