Terrestrial heat flow measurements on Lake Titicaca, Peru

Abstract

Between 29 May and 16 June, 1969, 19 succesful observations of terrestrial heat flow were made with Bullard-type probes on Lake Titicaca within the 250-m depth curve. The 19 heat-flow measurements have a mean of 1.32 μcal cm −2 sec −1 (u.f.u.) which is slightly below the continental average Thirteen of these observations were made with a 2.5-in-long probe and for the other six a probe 4.5 m long was used. The differences of temperature gradient found at four depths in the lake sediments can be accounted for by an annual variation of the bottom water of approximately 0.02°C by comparing them to the computed penetration into the lake bottom of an annual sinusoidal oscillation of the bottom water temperature. At each of five stations the water column was nearly isothermal from a depth of 50 m to the bottom. Above 50 m the temperature rises, reaching about 14°C at the surface. Newell has suggested that normal running faults along the axis of the lake separate an eastern Devonian-Cretaceous province from a western Tertiary province. This boundary lies just west of Isla Soto. The mean heat flow in the Tertiary province appears to be significantly higher than in the Devonian-Cretaceous province. This difference might reflect a greater content of radioactive elements in and under the Tertiary terrain.