AbstractExperiments to measure the energy released by the cryogenic weathering of sandstone and shale are described. The energy released by fracturing is thought to be proportional to the importance of new surfaces appearing in the rock at the time of disintegration. The specific surfaces of samples which have been submitted to freezing have been determined by an absorption technique. The energy released by disintegration of sandstone is about −400 Kj/m2of specific surface, and for shale is 700 Kj/m2. These values represent less than 1–2% of the heat flux of the frozen rock and have a negligible effect therefore, on the thermal region of the active la