Heat transfer in the lithospheric plates
Temperature is a fundamental parameter as it impacts on every physical properties or rocks (density, viscosity, conductivity, etc) and therefore on the thermal and mechanical properties of the Earth's lithospheres.
The continental geotherm, i.e. the distribution of temperature with depth, is a function of the rate at which heat is produced or consumed within the lithosphere, and the rate at which it is exchanged between the lithosphere an its surrounding.
We first review here the parameters involved in the mathematical definition of the continental geotherm. In a second part we will discuss the impact on the geotherm of a number of lithospheric deformation scenari.

Temperature and Heat
There are two types of geotherm: Steady state geotherms are those for which the temperature at any given depth does not change through time. In most cases, including in stable cratonic areas, geotherms are transient which means that at any given depth the temperature varies through time.
The temperature (degree of hotness or coldest) of a small volume of rock in the lithosphere varies if heat (a form of energy = kinetic energy) is gained or lost. The relationship that gives the variation of temperature as a function of a variation of heat is: dT=dE/(Cp.m), with Cp the heat capacity, and m the mass. The main causes changing the amount of heat contained in small volume or rock in the lithosphere are:

  • Heat conduction (transfer of kinetic energy between molecules or atoms)
  • Heat advection (replacement of a volume at temperature T1 with an equivalent volume at temperature T2)
  • Heat production (heat produced by radioactive isotopes, viscous heating, exothermic reactions)
  • Heat consumption (endothermic reactions)
The rate at which temperature changes depends on the rate at which heat is gained or lost. This gain or loss corresponds to the sum of the rates of the processes producing, consuming, or transporting heat. In the lithosphere the main mechanisms are: heat conduction, heat advection, and the heat produced by the decay of radiogenic isotopes.