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Introduction to What is Geothermal Energy?

How can humans can harvest Earth’s natural, subsurface heat in the form of geothermal energy? Heat at the Earth’s core is similar to the sun. The driving force to get this heat to the surface is the temperature differential between the Earth’s surface and its interior.

Earth possesses heat from its formation as a planet billions of years ago, as well as from the decay of radioactive isotopes present in Earth’s interior. Heat travels via conduction and convection to the surface where humans can utilize this energy in a variety of ways.

Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth’s interior. In areas where the geothermal gradient is greater, geothermal energy is most viable. These areas of high geothermal gradient can be predicted from patterns related to the geologic history of particular regions.

Why It Matters

Geothermal energy is a renewable energy resource that is available 24 hours a day, 365 days a year. Although the energy resource is everywhere, it can best be harnessed in locations with specific physical and geological conditions. Understanding these conditions is key to anticipating where specific types of geothermal projects could happen in the future.

Learning Objectives

  • Explain the basic structure of the Earth: core, mantle and crust.
  • Discuss how geothermal heat forms and why radiometric heating is so important
  • Summarize how heat moves from the interior of the Earth to Earth’s surface through both conduction and convection
  • Define a geothermal gradient
  • Describe geologic settings prone to high geothermal gradient, and thus, attractive geothermal systems for development
  • Understand the importance of the ‘ring of fire’

Images: “Soda Lake Control Room Sign” by Hilary Olson