Terrestrial heat flow in Ontario and Quebec

From some 1000 measurements of true rock temperatures, correct to 0.1°F, made at various depths in eight regions of Ontario and Quebec, average vertical temperature gradients for each location were obtained. Thermal conductivity measurements involving the preparation of approximately 300 rock specimens collected near the points of temperature measurement were carried out using the divided‐bar method. The terrestrial heat flow was computed for each region. The values obtained lie between 0.69 × 10 −6 and 1.05 × 10 −6 cal/cm 2 /sec. Statistical analysis and rejection criteria were employed to determine the best values and probable errors of the calculated heat flows. It was found that the variations in heat flow for the various regions were greater than the probable errors, the regions having the higher temperature gradients also having the greater heat flow. Broadly speaking, the regions of greater heat flow are located in the Grenville geological sub‐province while those with the lower are in the Superior subprovince.