CLAUS LUNAU / SCIENCE PHOTO LIBRARY CLAUS LUNAU / SCIENCE PHOTO LIBRARY
Geothermal mapping, USA. Map of the USA, showing the temperature at a depth of six kilometres below the surface. This shows areas with a high potential for boreholes to be drilled to those depths, to extract geothermal power. The colour-coded key shows temperatures in degrees Celsius: 50 (blue), 100 (green), 150 (yellow), 200 (orange), 250 (red) and 300 (brown).
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