Origin and Distribution of Polygonal Cracking of Rock Surfaces

When rocks weather, they sometimes develop striking polygonal patterns of shallow cracks. A review of the literature and field studies by the authors show that the cracking is much more widespread than has been generally recognised. Sandstones and granites are particularly susceptible, but other types of rock are also affected. The cracking is especially common and well developed in hot deserts, but there are some notable occurrences in the temperate zone. It rarely occurs in the humid tropics and in periglacial areas. There has been a continuing debate concerning its origin. Most of the existing theories fail to explain its geographical distribution. The present paper suggests that cracking is a direct or indirect consequence of surface crusting.