FAQs
How is geothermal heat created?
The heat from Earth’s core continuously flows outward. When temperatures and pressures become high enough, some of the surrounding rock melts, becoming magma. Because it is lighter, the magma rises, moving slowly up toward Earth’s crust, carrying with it the heat from below.
Sometimes the hot magma reaches the surface, where we know it as lava. Kilauea Volcano on the Big Island, for example, has been actively spewing lava since the 1980s. Most often the magma remains below Earth’s crust, heating nearby rock, rainwater and seawater that has seeped deep into the earth. Some of this hot water travels back up through faults and cracks and reaches Earth’s surface as hot springs or geysers. Most of it stays deep underground, trapped in cracks and porous rock. This natural collection of hot water is called a geothermal reservoir.