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Finding Geothermal Energy
What are the characteristics of geothermal resources? Some visible
features of geothermal energy are volcanoes, hot springs, geysers,
and fumaroles. But you cannot see most geothermal resources. They
are deep underground. There may be no clues above ground that a
geothermal reservoir is present below.
Geologists use different methods to find geothermal reservoirs. The
only way to be sure there is a reservoir is to drill a well and test the
temperature deep underground.
The most active geothermal resources are usually found along
major plate boundaries where earthquakes and volcanoes are
concentrated. Most of the geothermal activity in the world occurs
in an area called the Ring of Fire. This area borders the Pacific Ocean.
History of Geothermal Energy
Geothermal energy was used by ancient people for heating and
bathing. Even today, hot springs are used worldwide for bathing,
and many people believe hot mineral waters have natural healing
Using geothermal energy to produce electricity is a new industry.
A group of Italians first used it in 1904. The Italians used the natural
steam erupting from the Earth to power a turbine generator.
The first successful American geothermal plant began operating
in 1960 at The Geysers in northern California. There are now just
under 60 geothermal power plants in seven states, with many more
in development. Most of these geothermal power plants are in
California with the remainder in Nevada, Hawaii, Idaho, Montana,
What is Geothermal Energy?
The word geothermal comes from the Greek words geo (Earth) and
therme (heat). Geothermal energy is heat from within the Earth.
Geothermal energy is generated in the Earth’s core, almost 4,000
miles beneath the Earth’s surface. The double-layered core is made
up of very hot magma (melted rock) surrounding a solid iron center.
Very high temperatures are continuously produced inside the Earth
by the slow decay of radioactive particles. This process is natural in
Surrounding the outer core is the mantle, which is about 1,800 miles
thick and made of magma and rock. The outermost layer of the
Earth, the land that forms the continents and ocean floors, is called
the crust. The crust is three to five miles thick under the oceans and
15 to 35 miles thick on the continents.
The crust is not a solid piece, like the shell of an egg, but is broken
into pieces called plates. Magma comes close to the Earth’s surface
near the edges of these plates. This is where volcanoes occur. The
lava that erupts from volcanoes is partly magma. Deep underground,
the rocks and water absorb the heat from this magma.
We can dig wells and pump the heated, underground water to the
surface. People around the world use geothermal energy to heat
their homes and to produce electricity.
Geothermal energy is called a renewable energy source because
the water is replenished by rainfall and the heat is continuously
produced deep within the Earth. We won’t run out of geothermal