Oblique aerial photograph of the island of Ailsa Craig, looking east, Argyllshire


Oblique aerial view of the island of Ailsa Craig (off the south coast of Arran). Looking east. The precipitous cliffs are primarily the results of marine erosion but the initiation of a strongly positive topographic feature associated with the microgranite intrusion probably occurred during glaciation.

This is an intrusion of relatively fine-grained granite (microgranite) into Permian and Triassic sandstones.

The resistance of the microgranite to erosion compared to the response to the soft Permo-Trias sandstones into which it was intruded was of crucial importance during the phase of glacial erosion.

The principal direction of the ice during the last glaciation was south. This is indicated by the slight broadening of the island from north to south, albeit that this outline has been considerably modified by later marine action.

SCRAN ID: 000-000-147-771-C; British Geological Survey