Before it became the world’s largest geothermal power-producing site, The Geysers was known as the “Gates to Hades,” drawing visitors with its healing waters, steam vents, and wild legends.

Tiny earthquakes that result from slip or shear along a fracture caused by an uneven distribution of stress. The displacements are very small scale and unfelt at the surface. They can only be detected with sensitive equipment such as geophones and accelerometers, which can be deployed on the surface or in boreholes.
Brine In producing geothermal fields, this term refers to the hot water that is produced from wells. It is rarely as salty as implied. Instead, the salinities of most natural hot waters are commonly less than seawater, but they contain a wide range of rock-forming...
Cap Rock A poorly permeable or impermeable layer that overlies a geothermal reservoir. The term is borrowed from the oil industry and was once considered an essential feature of a producing geothermal resource in confining the flow and pressure of hot water....
Casing Shoe In geothermal wells, this is the bottom of the cemented casing string. Below the casing shoe, the well may be unprotected and open to the surrounding rock or lined with a slotted liner. The depth of the casing shoe generally coincides with the top of the...