Title of pamphlet: Geothermal energy: Power from the heat of the earthFigure 1. Worldwide installed production of electricity from geothermal energy (in megawatts) at 1.1.90 . - Figure 2: A gigantic underground reservoir of hot water. Figure 3: Process of tapping energy by the hot dry rock method. - Figure 4. Rock isotherms at 3000 metres below the earth's surface