The study of the earth's internal heat plays an important role in understanding the Earth's origin, internal constitution, and plate tectonics. The outflow of heat from the Earth's interior is, energy-wise, the most impressive terrestrial phenomenon. The present rate of heat loss is estimated to be about 1021 joules per year, which is orders of magnitude greater than the energy dissipation of earthquakes or heat loss from volcanic eruptions. Knowledge of terrestrial heat flow is essential in investigating the internal thermal field of the Earth. Initially focus has been on measurements of underground temperatures and thermal properties of geologic materials, assessment of sources and sinks of heat, institution of global data base, development of thermal models of crust and qualification of geothermal energy resources. During later stages, other implications of heat flow studies has also been recognized in fields such as paleoclimatology, global warming, exploration geophysics and hydrogeology. The International Heat Flow Commission – IHFC plays a guiding role in development of such investigations.
Heat loss from humans measured with a direct calorimeter and heat-flow meters