Geothermal (geology)
From Biocrawler, the free encyclopedia.
In geology, geothermal refers to heat sources within the planet. This article is primarily about heat within Earth.
The interior of Earth reaches temperatures of 5270 K. The planet's internal heat was originally generated during its accretion (see gravitational binding energy), and since then additional heat has continued to be generated by the decay of radioactive 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.
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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 7,200°F (4,000°C) or higher. [1] (http://www.biocrawler.com/encyclopedia/Geothermal_%28geology%29#endnote_eia9b1995)
- Much of the heat is believed to be created by decay of naturally radioactive elements. An estimated 45 to 85 percent of the heat escaping from the Earth originates from radioactive decay of elements concentrated in the crust.
- 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 form 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.[2] (http://www.biocrawler.com/encyclopedia/Geothermal_%28geology%29#endnote_Hollenbach2001)
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).
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.
References
- ^ "Geothermal Resources (http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/backgrnd/chap9b.htm)." DOE/EIA-0603(95) Background Information and 1990 Baseline Data Initially Published in the Renewable Energy Annual 1995. Accessed on May 4, 2005.
- ^ D. F. Hollenbach and J. M. Herndon (2001). "Deep-Earth reactor: Nuclear fission, helium, and the geomagnetic field". PNAS 98 (20): 11085-11090. DOI:10.1073/pnas.201393998 (http://dx.doi.org/10.1073/pnas.201393998)
See also
- Geothermal (disambiguation) for other uses of the word.
- Geothermal power
