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Earth cutaway from core to exosphere Geothermal drill machine in Wisconsin, USA. Temperature within Earth increases with depth. Highly viscous or partially molten rock at temperatures between 650 and 1,200 °C (1,200 and 2,200 °F) are found at the margins of tectonic plates, increasing the geothermal gradient in the vicinity, but only the outer core is postulated to exist in a molten or fluid ...
The red dotted-to-solid line depicts the average temperature profile with depth of soil in a permafrost region. The trumpet-shaped lines at the top show seasonal maximum and minimum temperatures in the "active layer", which commences at the depth where the maximum annual temperature intersects 0 °C. The active layer is seasonally frozen.
Temperature variations are most extreme at the surface of the soil and these variations are transferred to sub surface layers but at reduced rates as depth increases. Additionally there is a time delay as to when maximum and minimum temperatures are achieved at increasing soil depth (sometimes referred to as thermal lag).
Ground-source heat pumps take advantage of the difference between the ambient temperature and the temperature at various depths in the ground. The thermal properties of the ground near the surface [2] [3] can be described as follows: In the surface layer to a depth of about 1 meter, the temperature is very sensitive to sunlight and weather.
Soil temperature regulates seed germination, [70] breaking of seed dormancy, [71] [72] plant and root growth [73] and the availability of nutrients. [74] Soil temperature has important seasonal, monthly and daily variations, fluctuations in soil temperature being much lower with increasing soil depth. [75]
For example, snow cover and asphalt insulate the ground and homes can heat the ground (see also heat island). The line varies by latitude, it is deeper closer to the poles. The maximum frost depth observed in the contiguous United States ranges from 0 to 8 feet (2.4 m). [1] Below that depth, the temperature varies, but is always above 0 °C (32 ...
The thermal inertia of the shallow ground retains solar energy accumulated in the summertime, and seasonal variations in ground temperature disappear completely below 10m of depth. That heat can be extracted with a geothermal heat pump more efficiently than it can be generated by conventional furnaces. [ 10 ]
The cryic temperature regime distinguishes some higher-level groups. These regimes are based on the mean annual soil temperature (MAST), mean summer temperature, and the difference between mean summer and winter temperatures all at a soil depth of 50 cm. It is normally assumed that the MAST (in °C) equals the sum of the mean annual air ...