Geodiversity and Geoheritage value of balanced and pedestal rocks in South America

ABSTRACT

According to the Glossary of Geology “a balanced rock is a large rock resting more or less precariously on its base formed by weathering and erosion in place.” Popular usage extends a bit further, so balanced rocks come in many forms and have many names, quite apart from specific local names.

According to the Glossary of Geology a pedestal rock is “an isolated residual or erosional mass of rock supported by or balanced on a pedestal. The term is also applied to the entire feature.”

To the layman balanced rocks are amongst the most spectacular and intriguing of landforms, with a scientific and social significance much greater than their scarcity might suggest. Several quite different processes can produce balanced rocks, including differential erosion, surface weathering, deep weathering and stripping, induced tensional fracture, and marine erosion. Many attract tourists so have commercial as well as aesthetic and cultural value, and so feature in Geoheritage and Geotourism issues. Problems of balanced rocks include vandalism and the relatively modern practice of artificial rock stacking.

Most people are intrigued by balanced rocks, in which a huge rock appears to be balanced on underlying rocks, and often wonder “How did that rock get up there”.  They may acquire legends, and mythical explanations of their origin. People may come from far away to see them, and some develop a lucrative tourist trade. This may grow until management issues arise. Here we provide a scientific explanation of how balancing rocks are formed, and also discuss some of the management and social problems that they may create.

Spectacular examples of balanced rocks are frequently found in different environments in South America, particularly in cratonic areas, and some of them are presented in this paper.