Fitting Boulders: the Result of an Important Shore Process

Abstract

IN the course of petrological studies on the coastal outcrops of Constant Gneiss¹ to the south and west of West-port, New Zealand, some remarkable contact features of boulder against boulder/bedrock were observed. The adjacent boulders or boulder/bedrock have developed closely fitting mutual interfaces, and from the examples given here it can be seen that they are being eroded most rapidly by the processes acting along their interfaces. The phenomenon is therefore of considerable importance to coastal studies. Similar fitting boulders have now been observed in other environments. No reference to the phenomenon has been found in standard works on coastal processes and so I hope that this report will bring it to the notice of geologists and geographers working elsewhere in marine or lake shoreline environments.