Geothermal (geology)

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Geothermal (geology)

In geology

Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
, geothermal refers to heat sources within the planet. Geothermal is technically an adjective

Adjective

In grammar, an adjective is a word whose main syntax role is to grammatical modifier a noun or pronoun, giving more information about the noun or pronoun's definition....
(e.g., geothermal energy) but in U.S. English the word has attained frequent use as a noun

Noun

In linguistics, a noun is a member of a large, open class lexical category whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition....
(otherwise expressed as g. heat, g. source, or geotherm).

The planet's internal heat was originally generated during its accretion

Accretion (astrophysics)

In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravity attracting more matter, typically gaseous matter in an accretion disc....
, due to gravitational binding energy

Gravitational binding energy

The gravitational binding energy of an object consisting of loose material, held together by gravity alone, is the amount of energy required to pull all of the material apart, to infinity....
, and since then additional heat has continued to be generated by the radioactive decay

Radioactive decay

Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide....
of elements such as uranium

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
, thorium

Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....
, and potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
.

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Sources

Temperature within the Earth increases with greater 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 kelvin

Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
s.

Much of the heat is believed to be created by decay
Radioactive decay

Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide....
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.
Heat of impact and compression released during the original formation of the Earth by accretion of in-falling meteorite
Meteorite

A meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. While in space it is called a meteoroid....
s.
Heat released from the sinking of abundant heavy metals
Heavy metals

A heavy metal is a member of an ill-defined subset of elements that exhibit metallic properties, which would mainly include the transition metals, some metalloids, lanthanides, and actinides....
(iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
, nickel
Nickel

Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....
, copper
Copper

Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....
) as they descended to the Earth's core.
Some heat may be created by electromagnetic effects of the magnetic field
Magnetic field

A magnetism field is a vector field which can exert a magnetic force on moving electric charges and on magnetic dipoles . When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field....
s involved in Earth's magnetic field
Earth's magnetic field

Earth's magnetic field is approximately a magnetic dipole, with one magnetic pole near the north pole and the other near the geographic south pole ....
.
Heat generated within the Earth's core
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
may be in the range of 4–10 TW.
Heat may be generated by tidal force
Tidal force

The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force exerted on one body by a second body is not constant across its diameter....
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 approximately 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

Magma

Magma is molten Rock that is found beneath the surface of the Earth, and may also exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and gas bubbles....
is near to the surface. This primarily occurs in volcanic

Volcano

A volcano is an opening, or rupture, in a planet's surface or Crust , which allows hot, molten rock, ash, and gases to escape from below the surface....
and hotspot

Hotspot (geology)

In geology, a hotspot is a location on the Earth's surface that has experienced active volcano for a long period of time. J. Tuzo Wilson came up with the idea in 1963 that volcanic chains like the Hawaiian Islands result from the slow movement of a tectonic plate across a "fixed" hot spot deep beneath the surface of the planet....
areas and at spreading ridge areas. Iceland

Iceland

Iceland, officially the Republic of Iceland , is an island country located in the North Atlantic Ocean between mainland Europe and Greenland....
is a good example.

Geothermal (geology)

Sources

Heat flow

Hot spots

See also