Sea, old sculptor, carves from the western ramparts
Stack and cave and skerry,
Sweep harpist, with sagas of salt and stone.

George Mackay Brown

Alan Moar photography- Cliffs of Hoy with The Old Man of Hoy

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.

  • Amongst the many beauties of Orkney are the beaches which fringe the bays and ayres of the inner coast. These are dynamic forms, changing shape with the seasons and gradually retreating landward as sea level rises.

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  • Orkney is a dissected landmass drowned by postglacial sea level rise. A drop in sea level of just 35 m would unite the archipelago into a single island. The individual islands may represent hills that formed the watershed areas of preglacial drainage basins but it is linear glacial erosion which has separated one island from another and severed Orkney from the rest of Scotland.

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  • World coasts have seen sea-level variation of approximately 100 metres within the past 11,500 years through melting of the ice caps. When the ice caps melt the sea level rises globally (eustatically). The relative sea-level at any location is measured proportionate to the nearby land, which is itself subject to tectonic movement both up and down.

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