Inner Earth warmth
The earth's internal heat causes most of the geological processes and controls plate tectonics . The heat flow from the earth's interior to the surface is estimated at 47 terawatts (TW) and comes from two main sources in roughly equal amounts: radiogenic heat, which is produced by the radioactive decay of isotopes in the earth's mantle and crust , and primary heat, which is generated with the formation of the earth connected is. Despite its geological importance, this thermal energy, which comes from the bowels of the earth, only accounts for 0.03% of the total energy balance of the earth on the surface, on which the incident solar radiation predominates with a total heat flow of 173,000 TW. The solar radiation, which is partly reflected away and partly reaches the earth's surface, penetrates only a few tens of centimeters in the daily cycle and only a few tens of meters in the annual cycle. As a result, solar radiation is only minimally relevant for internal earth processes. Although the total internal heat flux of the earth to the surface is well measured, the relative contribution of the two main heat sources on earth, radiogenic and primary heat, is very uncertain as it is difficult to measure them directly. Chemical and physical models offer design ranges of 15–41 TW and 12–30 TW for radiogenic heat or primary heat.
Radiogenic heat
The radioactive decay of elements in the earth's mantle and in the earth's crust leads to the formation of daughter isotopes and the release of geoneutrino and thermal energy or radiogenic heat. Four radioactive isotopes are responsible for most of the radiogenic heat due to their enrichment compared to other radioactive isotopes: uranium-238 ( 238 U), uranium-235 ( 235 U), thorium -232 ( 232 Th) and potassium -40 ( 40 K). Geoneutrino detectors can record the decay of 238 U and 232 Th and thus estimate their contribution to the existing radiogenic heat budget, while 235 U and 40 K are not recorded in this way. However, an analysis of the results of the Geoneutrino's measurement yielded an estimate that half of the Earth's total internal heat source is radiogenic, which is in line with previous estimates. Due to the lack of rock samples at depths below 200 km, it is difficult to accurately determine the radiogenic heat throughout the mantle. With regard to the depths under the mantle, geochemical studies show that due to the expected low concentration of radioactive elements here, radiogenic heat is not believed to play a significant role in the Earth's core . The generation of radiogenic heat in the earth's mantle is also linked to the structure of mantle convection, which is much discussed. It is believed that the shell may have a layered structure with a higher concentration of radioactive elements in the lower shell, or that small areas enriched with radioactive elements are distributed throughout the shell.
Primary warmth
The original formation of the dense core of the earth led to overheating and rapid heat loss. After the jacket hardened, the rate of heat loss slowed down. The heat flow from the core is currently sufficient to sustain the convective outer core, as well as the earth's geodynamics and magnetic field.
Individual evidence
- ↑ a b J. H. Davies, DR Davies: Earth's surface heat flux . In: Solid Earth . tape 1 , no. 1 , February 22, 2010, p. 5–24 , doi : 10.5194 / se-1-5-2010 ( semanticscholar.org [PDF]).