The temperature is 100 degree Celsius three miles beneath the earth. This is an ideal temperature to boil water to generate a steam-powered electric power plant. However, drilling three miles below the earth, though possible is a Herculean task. Instead, geothermal hotspots are identified to derive geothermal energy. A geothermal hotspot is an area that transmits excess internal heat from the interior of the earth to the outer crust because of the reduced thickness in the earth's mantle. Geothermal hotspots could be used to generate electricity.
One of the methods to generate electricity from geothermal energy is by pumping hot water into sedimentary hotspots. The steam generated by this method is used to produce electricity. The condensed steam is again circulated into the permeable sedimentary stream of a hotspot.
Another method is by using volcanic magma. The temperature of partially molten magma is approximately 650 degree Celsius. This heat is used to boil water to generate electricity.
Some geothermal plants also use the hardened magma that is extremely hot. This system uses hot dry rock. Pipes are looped through these hot dry rocks through which water is circulated. The heat of the rocks converts the water into steam prior to transferring the heat to a steam generator.