In a recent study by McFadden et. al. (2005), it was proposed that; the north-south near vertical orientations of many rock surface cracks, relate to thermal stresses that arise daily from non-uniform solar heating, and that this mechanism is viable in other climates. This is based on clast and crack orientation data from eight sites in the deserts of North America. In this study, the presence of north to south cracking, potentially related to thermal stresses is confirmed at the study site in Wadi Shehah, the United Arab Emirates (UAE). However the proposed mechanism did not account for the majority of crack orientations, and a significantly smaller percentage of cracks with north-south orientations were recorded at the site in Wadi Shehah compared to the North American sites. This suggests that the mechanism is ‘viable’ in the UAE, but both less important, and less dominant as a process of rock breakdown than in the higher latitude North American deserts. Dominance of bi-modal and multi-modal crack orientations emphasize the significance of other processes and mechanisms in the initiation of cracking at this site, as well as solar insolation.
