Measuring heat fluxes at the surface of Earth in oceanic areas
 
To measure the heat flux in a given point of the Earth surface requires knowing the thermal conductivity of the soil as well as the temperature gradient. Thermal conductivity is determined in by analysis of a soil sample and the temperature gradient by measuring the temperature at various depths.
 
If, in emerged area, this is done by drilling, under the ocean a sampling tube is used. The tube penetrates the superficial layer of the ground by its own weight sampling soil and determines the temperature gradient by measuring the temperature at various points along its length.