W. M. Adams, G. Watts, and G. Mason
Estimation of thermal diffusivity from field observations of temperature as a function of time and depth
American Mineralogist (August 1976), 61(7-8):560-568

Abstract:
Methods have been previously reported for estimating the thermal conductivity from field observations; application of several such methods gives results that differ significantly from one another. The cause of the discrepancy appears to be that each method only utilizes some of the information contained in the data. Therefore, a method has been developed that uses all of the information, giving a "best" answer, in this sense. The method has been applied to data taken from beneath Lake Waiau, a tarn on Mauna Kea, Hawaii. Observations taken over more than two years at depths in the sediments to about ten meters are used to estimate the thermal diffusivity of the sediment. The thermal conductivity of some sediment samples has been measured in laboratory apparatus for comparison with the field results.