The sheer cliffs of Fowlsheugh are actually undercut in some places by erosive force of the North Sea wave action and associated strong marine winds, giving rise to cliff overhangs in numerous stretches of the blufftop trail. (Off shore winds commonly attain mean velocities of 80 kilometres per hour here, especially in winter months.) The underlying rock formation is known as Old Red Sandstone, which occurs from Dunnottar Castle five kilometres north to the town of Catterline seven kilometres south. This sandstone formation may be as thick as 2700 metres.