What is geothermal energy? The term geothermal comes from the Greek geo meaning earth and therine meaning heat, so geothermal energy is the energy derived from the natural heat of the earth. Heat flowing from the Earth's warm interior due to movements of crustal plates, areas of high heat flow, can be localized near the surface where convective circulation plays a significant role in bringing heat near the surface (Bank Group World, 2012). The Earth's crust, on which we live and depend, is largely the product of millions of once-active volcanoes and enormous volumes of magma that did not erupt but instead cooled beneath the surface. Such persistent and widespread volcanism has given rise to many valuable natural resources around the world. ... Groundwater heated by large, still hot magmatic bodies can be exploited to produce geothermal energy. -- Excerpted from: Brantley, 2014, Volcanoes of the United States, USGS general interest publication. Deep groundwater circulation along fracture zones will carry heat to shallower levels, collecting heat flow from a wide area and concentrating it in shallow reservoirs or discharging it as heat. soft. These tanks can hold hot and/or stream water. By drilling these reservoirs, hot water and/or steam is conveyed to the surface where it is used for direct-use applications, or high-pressure steam is separated to drive turbines for power generation. The energy-efficient wastewater from such power generation is then usually re-injected into the reservoir or further used for direct heat applications. This technology allows it to be used to generate electricity and provide domestic and industrial heat. Geothermal energy has proven to be reliable, economical, environmentally friendly and renewable (World Bank Group, 2012). In general there are two main categories, (1) high temperature resources and (2) moderate/low temperature resources. High-temperature geothermal resources – 220 degrees Celsius and above – are predominantly found in volcanic regions and island chains. Moderate to low temperature resources are found on all continents. High-temperature resources are almost always used for energy production, while most low-temperature resources are used for direct heating purposes or for agriculture and aquaculture. How does the exploitation of geothermal energy work? Deep wells, a mile deep or more, can tap into reservoirs of steam or very hot water that can be used to drive turbines that power electricity generators. There are 3 types of geothermal power plants in use today, and they are: