The terrestrial heat-flow density (simply called ‘heat flow’) is a measure of thermal energy flowing from the core towards the Earth’s surface, it varies locally and is given as the rate of heat transferred across an area per unit time. Heat flow provides indispensable insights into the evolution of our planet and is paramount for the analysis of the Earth’s temperature field across spatial scales and time domains. It improves our understanding of geodynamic processes and complex tectonic structures, the transient counter equilibrium of glacial cooling events, and the basic mantle heat flow entering the overlying crustal rocks. Therefore, heat-flow values are systematically determined in continental and marine settings, e.g., during scientific drilling projects conducted in the global framework of the International Ocean Drilling Program (IODP) and the International Continental Scientific Drilling Program (ICDP).
Based on past and present observations, heat-flow data form the basis to decipher the future behaviour of thermal geosystems. Reliable data are a prerequisite for thermal modelling - as boundary condition, validation or calibration input - of various geoenergy aspects (resource assessment and exploitation of geothermal or hydrocarbon systems, long-time and safe geological storage of energy and waste, management and prevention of subsurface utilization conflicts, etc.). In the context of the on-going global energy system transition, a well-documented access to parameters and processes of subsurface thermal systems, i.e. the heat flow, is of utmost importance.