A method and apparatus for locating hydrocarbon deposits includes temperature 16 sensor for measuring earth surface temperature at each of a plurality of locations, and a solar absorption sensor 14 for measuring the absorption coefficient of the earth's surface at each of those plurality of locations. A sky temperature sensor 18 may also be provided. A computer 30 records measurements as a function of location, and outputs a plot of corrected surface temperatures as a function of the geographic location of the measurements. By comparing corrected surface temperature measurements at the plurality of locations, a hydrocarbon deposit may be located and its boundaries determined.