Geothermal Energy 1.
Geothermal energy comes from the heat within the earth.
People around the world use geothermal energy to produce electricity, to heat buildings and greenhouses, and for other purposes. The earth's core lies almost 4,000 miles beneath the earth's surface. The double-layered core is made up of very hot molten iron surrounding a solid iron center. Heat is continuously produced within the earth by the slow decay of radioactive particles that is natural in all rocks. Surrounding the earth's core is the mantle, thought to be partly rock and partly magma.