geotherm

Geotherm refers to the temperature distribution within the Earth as a function of depth. It is typically represented by a geotherm profile or curve that shows how temperature increases with increasing depth in a given region. The shape and gradient of a geotherm depend on factors such as crustal composition, tectonic setting, heat production from radioactive decay, and groundwater movement, among others. In the upper crust, geotherms are often approximated by a roughly linear geothermal gradient, while deeper or tectonically complex zones may require more detailed, non-linear models. The gradient is usually expressed as dT/dz, the rate of temperature change with depth.

Geotherms can be inferred from direct measurements and indirect methods. They are estimated from borehole temperature data, rock temperature measurements, and information gathered from geothermal reservoirs, or from heat-flow data combined with thermal conductivity estimates. The global crust shows substantial variation in gradients: continental crust commonly exhibits gradients roughly in the order of 20–30 °C per kilometer in many regions, but gradients can be higher in volcanically active areas and lower in stable cratons.

Applications of geotherm studies include assessing geothermal energy potential, constraining thermal models of tectonics and metamorphism, evaluating hydrocarbon maturation, and informing models of crustal evolution. Limitations arise from spatial variability, uncertainties in rock conductivity, and the challenge of extrapolating shallow measurements to greater depths.