Sea, old sculptor, carves from the western ramparts
George Mackay Brown
Image courtesy of Alan Moar
The outer coast of Orkney is an outstanding location to study the erosion of hard rock coasts. Evidence of major erosion is not hard to find. The great bowl of Enegars corrie is losing its edge to the sea. The egg-shaped headland of Marwick Head is a dome half lost. Historical records mention the collapse of cliffs and arches - most notably at the Old Man - and the scars of recent cliff falls shine to catch the eye. This dynamism reflects the ferocity of North Atlantic storms and major changes at the coast can often be linked to the greatest storms. Rates and styles of marine erosion and cliff retreat can be assessed on Orkney, unlike on many other coasts where change is very slow.
The effects of rock type and structure are also simplified. The Devonian sandstone are often flat-lying and divided into cuboidal blocks of various sizes by bedding planes and joints. Marine erosion attacks an ancient but simple masonry, allowing classic models of cliff evolution to be tested.
As elsewhere in Scotland, elements of the more sheltered part of the Orkney coastline are inherited from the period before the last ice sheet. The firths are products of many phases of glacial erosion and the shore platforms that edge them often pass below till left by the last ice sheet.