Query: The amount of heat energy coming out of the Earth is too small to even be worth considering.

Relevant passages:
Earth <=SEP=> Earth ( from Eorðe -LSB- Γαῖα , Gaia -RSB- Terra ) , otherwise known as the World or the Globe , is the third planet from the Sun and the only object in the Universe known to harbor life . It is the densest planet in the Solar System and the largest of the four terrestrial planets .   According to radiometric dating and other sources of evidence , Earth formed about 4.54 billion years ago . Earth 's gravity interacts with other objects in space , especially the Sun and the Moon , Earth 's only natural satellite . During one orbit around the Sun , Earth rotates about its axis over 365 times ; thus , an Earth year is about 365.26 days long . Earth 's axis of rotation is tilted , producing seasonal variations on the planet 's surface . The gravitational interaction between the Earth and Moon causes ocean tides , stabilizes the Earth 's orientation on its axis , and gradually slows its rotation .   Earth 's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years . About 71 % of Earth 's surface is covered with water , mostly by its oceans . The remaining 29 % is land consisting of continents and islands that together have many lakes , rivers and other sources of water that contribute to the hydrosphere . The majority of Earth 's polar regions are covered in ice , including the Antarctic ice sheet and the sea ice of the Arctic ice pack . Earth 's interior remains active with a solid iron inner core , a liquid outer core that generates the Earth 's magnetic field , and a convecting mantle that drives plate tectonics .   Within the first billion years of Earth 's history , life appeared in the oceans and began to affect the Earth 's atmosphere and surface , leading to the proliferation of aerobic and anaerobic organisms . Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago . Since then , the combination of Earth 's distance from the Sun , physical properties , and geological history have allowed life to evolve and thrive . In the history of the Earth , biodiversity has gone through long periods of expansion , occasionally punctuated by mass extinction events . Over 99 % of all species that ever lived on Earth are extinct . Estimates of the number of species on Earth today vary widely ; most species have not been described . Over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival . Humans have developed diverse societies and cultures ; politically , the world has about 200 sovereign states .

Geothermal energy <=SEP=> Geothermal energy is heat energy generated and stored in the Earth . Thermal energy is the energy that determines the temperature of matter . The geothermal energy of the Earth 's crust originates from the original formation of the planet and from radioactive decay of materials ( in currently uncertain but possibly roughly equal proportions ) . 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 .   Earth 's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth 's formation . Temperatures at the core -- mantle boundary may reach over 4000 ° C ( 7,200 ° F ) . The high temperature and pressure in Earth 's interior cause some rock to melt and solid mantle to behave plastically , resulting in portions of the mantle convecting upward since it is lighter than the surrounding rock . Rock and water is heated in the crust , sometimes up to 370 ° C ( 700 ° F ) .   From hot springs , geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times , but it is now better known for electricity generation . Worldwide , 11,700 megawatts ( MW ) of geothermal power is online in 2013 . An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating , space heating , spas , industrial processes , desalination and agricultural applications as of 2010 .   Geothermal power is cost-effective , reliable , sustainable , and environmentally friendly , 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 .   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 . Forecasts for the future of geothermal power depend on assumptions about technology , energy prices , subsidies , plate boundary movement and interest rates . Pilot programs like EWEB 's customer opt in Green Power Program show that customers would be willing to pay a little more for a renewable energy source like geothermal . But as a result of government assisted research and industry experience , the cost of generating geothermal power has decreased by 25 % over the past two decades . In 2001 , geothermal energy costs between two and ten US cents per kWh .