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Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%
Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet (20%) and fromradioactive decay of minerals (80%).[1] The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (ge), meaning earth, and θερμος (thermos), meaning hot.
The heat that is used for geothermal energy can be stored deep within the Earth, all the way down to Earth’s core – 4,000 miles down. At the core, temperatures may reach over 9,000 degrees Fahrenheit (5000 degrees Celsius). Heat conducts from the core to surrounding rock. Extremely high temperature and pressure cause some rock to melt, which is commonly known as magma. Magma convects upward since it is lighter than the solid rock. This magma then heats rock and water in the crust, sometimes up to 700 degrees Fahrenheit (370 degrees Celsius) [2]
From hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heatingsince ancient Roman times, but it is now better known for electricity generation. Worldwide, about 10,715megawatts (MW) of geothermal power is online in 24 countries. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications.[3]
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,[4] but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.
The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive.[citation needed] Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, and interest rates.
