The measurement of the flow of heat through the crust of the earth and through rocks

Abstract

Methods of rapidly measuring the temperature gradient in and the thermal conductivity of the rocks in the upper part of the crust of the earth are described A thermistor is used to indicate temperatures in boreholes to within 0. 02 degree C. It has been found possible to detect and locate to within one or two feet the base of porous ;strata through which water is flowing into the borehole. A steady state apparatus has been constructed hich, within 10 minutes, gives values of the thermal esistance of a disc of rock. It has been used to nvestigate the effect of water content on the thermal conductivity of porous rocks as well as for making outine measurements; surprisingly large changes of onductivity have been found for small changes in moisture Content. Methods for the rapid preparation of discs of rock have also been investigated. Evidence is presented for questioning the reliability of thermal conductivities obtained in the aboratory for coarse grained rocks; it is suggestedthat slides of the rocks should be made and examined before deciding on a suitable thickness for each disc. n an attempt to determine whether laboratory rsults give true "in situ" conductivities a thermal conductivity probe was constructed but although the esults were promising there, were too few to allow a efinite conclusion to be reached. Uncorrected mean values for the heat flux were 2.3x 1o-6 cal./sq. cm./sec. for Tasmania and 2.2 x 10-6 : cal./sq. cm./sec. f'or the Snowy Mountains area. Show more