Geothermal (geology)


Geothermal (geology)

In geology, geothermal refers to heat sources within the planet. Strictly speaking, "geo"-thermal necessarily refers to the Earth but the concept may be applied to other planets.

"Geothermal" is technically an adjective (e.g., "geothermal energy") but in U.S. English the word has attained frequent use as a noun (otherwise expressed as "g. heat, g. source, or geotherm").

The planet's internal heat was originally generated during its accretion, due to gravitational binding energy, and since then additional heat has continued to be generated by the radioactive decay of elements such as uranium, thorium, and potassium. The heat flow from the interior to the surface is only 1/20,000 as great as the energy received from the Sun.

Sources

Temperature within the Earth increases with increasing depth. Highly viscous or partially molten rock at temperatures between 1,200 and 2,200 °F (650 to 1,200 °C) is postulated to exist everywhere beneath the Earth's surface at depths of 50 to 60 miles (80 to 100 kilometers), and the temperature at the Earth's center, nearly 4,000 miles (6,400 kilometers) deep, is estimated to be 5650 ± 600 kelvins. cite journal|title=Thermodynamics from first principles: temperature and composition of the Earths core|journal=Mineralogical Magazine|date=2003-02-01|first=D.|last=Alfe|coauthors=M. J. Gillan, G. D. Price|volume=67|issue=1|pages=113–123|doi= 10.1180/0026461026610089|url=http://www.es.ucl.ac.uk/people/d-price/papers/153.pdf|format=PDF|accessdate=2007-03-01] cite news | first=Gerd | last=Steinle-Neumann | coauthors= Lars Stixrude, Ronald Cohen | title=New Understanding of Earth’s Inner Core | date=2001-09-05 | publisher=Carnegie Institution of Washington | url =http://www.carnegieinstitution.org/news_010905.html | work = | pages = | accessdate = 2007-03-01 | language = ]

* Much of the heat is believed to be created by decay of naturally radioactive elements. An estimated 45 to 90 percent of the heat escaping from the Earth originates from radioactive decay of elements within the mantle.cite news | first=Joe | last=Anuta | title=Probing Question: What heats the earth's core? | date=2006-03-30 | publisher=physorg.com | url=http://www.physorg.com/news62952904.html | accessdate = 2007-09-19 ]
* Heat of impact and compression released during the original formation of the Earth by accretion of in-falling meteorites.
* Heat released from the sinking of abundant heavy metals (iron, nickel, copper) as they descended to the Earth's core.
* Some heat may be created by electromagnetic effects of the magnetic fields involved in Earth's magnetic field.
* Heat generated within the Earth's core may be in the range of 4–10 TW. cite journal|title=Thermodynamics from first principles: temperature and composition of the Earths core|journal=PNAS|date=2001-09-25|first=D. F. |last=Hollenbach|coauthors=J. M. Herndon|volume=98|issue=20|pages=11085–11090|doi= 10.1073/pnas.201393998|pmid=11562483|url=http://www.pnas.org/cgi/content/full/98/20/11085|format=|accessdate=2007-03-01]
* Heat may be generated by tidal force on the Earth as it rotates, since land cannot flow like water it compresses and distorts, generating heat.

Heat flow

Heat flows constantly from its sources within the Earth to the surface.Global terrestrial heat flow is about 45 TW (1 TW = 1012 watts).This is very approx 1/10 watt/square meter (which is about 1/10,000 of solar irradiation).

Hot spots

Geothermal heat at the surface is highly concentrated where magma is close to the surface. This primarily occurs in volcanic and hotspot areas and at spreading ridge areas. Iceland is a good example.

See also

* Geothermal power
* Hydrothermal circulation

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Geothermal heating — has been used since the time of the Roman Empire as a way of heating buildings and spas by utilizing sources of hot water and steam that exist near the Earth s surface. [Climate.Org Renewable Energy: Geothermal,… …   Wikipedia

  • Geothermal — is related to energy and may refer to: * Geothermal (geology), heat that comes from within the Earth * Direct exchange geothermal heat pump, a method of heating and cooling with the energy of the earth using direct exchange of heat * Geothermal… …   Wikipedia

  • Geothermal power in the United Kingdom — The potential for exploiting geothermal energy in the United Kingdom on a commercial basis was initially examined by the Department of Energy in the wake of the 1973 oil crisis. Several regions of the country were identified, but interest in… …   Wikipedia

  • geology — /jee ol euh jee/, n., pl. geologies. 1. the science that deals with the dynamics and physical history of the earth, the rocks of which it is composed, and the physical, chemical, and biological changes that the earth has undergone or is… …   Universalium

  • Geology of New Zealand — The continent of Zealandia The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. New Zealand was earlier part of the… …   Wikipedia

  • Geothermal heat pump — A geothermal heat pump system is a heating and/or an air conditioning system that uses the Earth s ability to store heat in the ground and water thermal masses. These systems operate based on the stability of underground temperatures: the ground… …   Wikipedia

  • Geothermal areas of Yellowstone — Map of all coordinates from Google Map of all coordinates from Bing Export all coordinates as KML …   Wikipedia

  • Geology of Tasmania — Tasmania has a varied geological history, with the world s biggest exposure of diabase, or dolerite. Rocks from the Neoproterozoic, Paleozoic and Mesozoic time periods appear. It is one of the few southern hemisphere areas glaciated during the… …   Wikipedia

  • Geothermal areas in Lassen Volcanic National Park — ImageStackRight|200 Several groups of hot springs and fumaroles, remnants of former volcanic activity, exist in Lassen Volcanic National Park. Most of these lie in or are closely adjacent to Mount Tehama s caldera. Bumpass Hell is the most… …   Wikipedia

  • Geology of the Lassen volcanic area — The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California, U.S.. The park is located in the southernmost part of the Cascade… …   Wikipedia


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.