VERTICAL VARIATION OF HEAT-FLOW DENSITY IN THE CONTINENTAL-CRUST

Terrestrial heat flow density is a key parameter in understanding the past, present and future development of our planet. Most phenomena stu died in deep crustal geophysics are temperature dependent and therefor e reliable assesments of deep temperatures are necessary. Most heat fl ow measurements have been made in drill holes which are shallow (< 1 k m) in comparison to the thicknesses of the crust and lithosphere. The recent findings in deep drilling projects (e.g. the Kola deep hole in Russia and the KTB hole in Germany) have yielded results which suggest that there is a distinct contrast between heat flow densities measure d in the uppermost 1 km and values measured at deeper levels. The fact ors contributing to the vertical variation in the uppermost few kilome tres are discussed with special emphasis on palaeoclimatic ground surf ace temperature changes and groundwater circulation in the bedrock.