erosion surfaces

preglacial drainage

folding and landforms

faulting and landforms

Northern North Sea

sub-Devonian terrain

The rolling preglacial terrain of northern Hoy, now truncated and dissected by sea cliffs and glacially-deepened valleys

 

Image courtesy of Alan Moar

 

Preglacial landscapes

The landscape of Orkney before the Ice Age can be reconstructed from the fragments of ancient landforms that have escaped erosion by the great ice sheets. Although no sediments of Tertiary age exist on land, the adjacent submarine shelves on the northern North Sea and the Atlantic carry thick covers of sediments that provide important evidence of events on the intervening land area. Orkney also provides fine examples of structural landforms developed by weathering and erosion of tilted, folded and faulted Devonian sandstones. The oldest land surfaces are those which bare presently emerging through erosion of Devonian cover rocks.