Geothermal energy is thermal energy generated and stored in the Earth. The term geothermal originates from the Greek words geo (earth) and therme (heat). This energy is a sustainable and renewable resource because the Earth constantly produces heat within its interior. Humans harness geothermal heat for various applications, including bathing, heating buildings, and generating electricity.
The Earth’s Internal Heat: A Deep Source
Geothermal energy is primarily produced by the slow and continuous radioactive decay of naturally occurring radioactive isotopes within the Earth’s core. This process, which occurs in all rocks, releases heat.
The Earth is composed of four primary layers:
- Inner Core: A solid sphere of iron, approximately 1,500 miles in diameter.
- Outer Core: A layer of molten rock, known as magma, about 1,500 miles thick.
- Mantle: A dense layer of magma and rock surrounding the outer core, extending about 1,800 miles in thickness.
- Crust: The outermost solid layer of rock that forms the continents and ocean floors. Its thickness varies from 15 to 35 miles under continents and 3 to 5 miles under oceans.
Scientific measurements indicate that the temperature of the Earth’s inner core reaches an astounding 10,800 degrees Fahrenheit (°F), comparable to the surface temperature of the Sun. The mantle’s temperature ranges from approximately 392°F at its boundary with the crust to about 7,230°F near the core. Rocks and water deep beneath the Earth’s surface absorb this heat from the surrounding magma, resulting in higher temperatures at greater depths.
The Earth’s crust is divided into tectonic plates. Magma rises closer to the surface along the boundaries of these plates and can escape through gaps, leading to volcanic activity. Magma that erupts onto the Earth’s surface is termed lava.
