Origin Of Earth'S Heat
At the end of the 17th century, the Earth was conceived as a molten mass with a solid crust as a result of its cooling. It was not until the 19th century that the first calculations of the age of the Earth based on its thermal evolution were drawn up, and the term geothermal was first defined as the scientific discipline that studies earth's heat, origin of this heat, distribution and use.
Precisely, the use of this thermal energy is what has led to the development of geothermal energy. Geothermal energy allows us to take advantage of the heat energy inside the Earth in different applications, using the laws of thermodynamics.
The Earth is a warm body immersed in a cold space that loses temperature continuously at a rate of 130ºC for every 1,000 million years.
The origin of Earth's heat
The origin of terrestrial heat is the sum of physical and chemical processes that take place differently in its interior.
The following describes the different processes that originate the Earth's heat, considering the part of the interior of the planet where they take place.
- Latent heat of crystallization: it is the limit between the inner core and the outer core. The inner core is in the solid state while the outer core is in the liquid state. In the outer core, crystallization reactions are continuously produced; these reactions are exothermic and therefore cause heat. This heat is known as the latent heat of crystallization.
- Gravitation. Gravity exerts a compressive force towards the center of the planet, and in the process of contraction of the Earth's mass frictional heating is generated.
- Heat remaining planet formation: This is the heat, although present, product of the collisions between the stellar residues of the protoplanetary disk that gave rise to the Earth.
- Heat kinetic or friction: between the outer core and the mantle. It is the energy in the form of heat that is released as a result of the friction that is produced by the different responses that the outer core and the mantle have before the field of efforts of the Moon and the Sun (tidal forces).
- Exothermic physicochemical reactions: mantle. The high pressures and high temperature make the minerals unstable and continuous phase changes that generate energy in the form of heat occur.
- Radiogenic decay of isotopes: bark and mantle. The rocks that make up the lithosphere (composed of the crust and the highest part of the mantle) are rich in minerals that contain radioactive elements such as the isotopes 235U, 238U, 232Th and 40K. The decomposition reactions of these isotopes are exothermic. The radiogenic decay of isotopes is the process that brings the most heat to the surface of the Earth.
It is necessary to take into account that the temperature of the Earth increases inwards from a global average in surface of 15ºC to more than 5000ºC in the inner core.
Last review: January 2, 2018