Geothermal Energy

    Since ancient times, people have been trying to understand and harness geothermal energy. Some components of this mystery still remain to be discovered but here are the basics that we already know.

    The word geothermal has two components. Geo meaning land or earth; thermal meaning heat. Then this means that geothermal energy is energy from our planet's heat.

   The source of this heat is deep within the Earth, at its center, or its core. The inner core is thought to be solid and made up of iron and nickel. The outer core contains the same metals as the inner core but in a molten state. It is extremely difficult to imagine just how how hot the Earth's core is because the temperatures measure thousands of degrees. 

    The hot core of solid and molten metals is surrounded by the mantle, a solid rock that believe it or not is also hot. This mantle is cover by a thin outer called the crust. This crust is the part of the Earth we live on. Although the core is the hottest part of the Earth the heat spreads outward through the mantle and finally to the crust.

Move Mouse Over This to see a diagram of the Earth.

    This intense heat is continually produced under the Earth's crust and is mostly from the decay of naturally radioactive materials like uranium. The amount of heat 10,000 meters below the surface contains 50,000 times more energy than all the oil and natural gas resources in the world.

    Geologists - scientists who study the Earth - have discovered that the temperature within the layers of the Earth increases with depth. The relationship between temperature and depth is called geothermal gradient. This geothermal gradient is not the same all over the Earth; some areas have higher temperatures closer to the surface than other areas. There are many different reasons for this temperature variation. In volcanic areas, the Earth's crust is hotter because it, or the mantle below it, contains molten rock called magma. These "hot spots" occur at plate boundaries or at places where the crust is thin enough to let the heat through. The Pacific Rim, which is called the "ring of fire" for all of its volcanoes, has many hot spots. These hot spots are the main sources of geothermal energy that are available to humans.

Mouse Over to see the relative geothermal gradient for the United States.

   In many geothermal areas the energy is used to provided power. In California, Nevada, and other places around the world, geothermal energy produces electricity in large power plants. Geothermal energy provides about 5 percent of California's electricity, and a third of El Salvador's. In Idaho and Iceland, geothermal heat is used to warm buildings and for other applications.

    Geothermal energy is used in many ways, but in Yellowstone the features that the geothermal energy creates are protected by law and must remain undisturbed.