The origin and development of surface depressions in the Mendip Hills

Abstract

This study aims to provide a systematic classification of the numeroustypes of sinkhole mentioned in the morphological literature. As three types of stream sink are readily identifiable from their morphologicalrelationship with a valley, the main part of the investigation is concentrated upon enclosed circular depressions of other origin. Two hypotheses, formation by surface solution and formation by collapse into underground cavities, were tested in the Mendip Hills. No evidence has been found to support the idea that surface solution can form circular sinkholes. Collapse sinks of different forms have been arranged in a developmental sequence.The four stages of the karstic cycle have been redefined, coupling the same visual criteria as used before with a new rationale of process and development. This rationalised version of the karstic cycle suggests that Cheddar Gorge is more likely to have originated as a surface valley than by the collapse of underground caverns.