Steam to Electricity
To understand how electricity is produced at The Geysers, it is helpful to know
how geothermal energy begins. Molten rock, or magma, exists very deep in the earth
where temperatures are extremely high. However, magma is relatively close to the
surface in a few areas, particularly the volcanically active areas around the Pacific
Rim. At The Geysers, the magma is believed to exist at least four miles below the
earth's surface. The heat from the magma radiates to the layers of rock above, heating
water in the pores and fractures of the hot rock. A small portion of the heated
water may rise to the surface, creating hot springs, geysers and fumaroles. At The
Geysers, the reservoir water boils to steam and is trapped by an overlying layer
of tight, unfractured rock, called cap rock.