Photogrammetry of the Emerged Rocks at Rocas Alijos

Abstract

Photographic and photogrammetric records of the emerged rocks at Rocas Alijos are of interest on several accounts: First, the relatively young age of the emerged rocks at Rocas Alijos implies relatively rapid erosion. Furthermore, the loose, blocky nature of the material, and the complete disappearance of the fourth rock pictured in the etching from the 1837 Venus expedition (Skinner and Schmieder, 1996), suggest that the erosion is intermittent. Rather than a constant slow removal of material by aqueous solution, salt heaving, and similar microscopic processes, it is likely that major mass loss occurs by intermittent failure of joints or supports, resulting in sporadic sudden failure and collapse, perhaps stimulated by periods of violent weather or earthquakes. Human agents, such as aerial bombardment, may have been a significant factor historically. Thus, a photographic record could enable tracking of these events and thereby an estimation of the projected life of the structures.