The Coast
Much of Scotland's coast is composed of relatively resistant rocks. There are significant lengths of softer material, predominantly of sands with finer silt and muds, in shallow sheltered bays and in estuaries.
Rocky Coasts
The rocky coastlines are characterised by cliffs ranging from a few metres to a few hundred metres in height. Some end at, or near, the present sea level, whereas others plunge well below it. Some have remnants of older sea levels in the form of terraces cut into the rock, regardless of its structure or resistance, but their dates are unknown.
Caves, headlands and bays occur alongside blow holes where part of the cave roof has collapsed, or geos where the whole roof has collapsed and from which arches and, ultimately, stacks are formed. Here the sea has exploited weaknesses in the bedding planes, joints, cracks and faults of the rocks. The processes of formation and decay of these features are still active and the powerful erosive energy of the sea is evident from the collapse of cliffs and the smoothing of the debris produced. Overall, the coast in rocky areas is perhaps best described as the accidental coincidence of the sea resting at the land edge.
Soft Coasts
The softer coasts are easier to date and show change more obviously. It is likely that the debris derived from glacial erosion was deposited by ice and meltwater in the present coastal area in vast amounts. What we see now is the result of a progressive redistribution over the past 14,000 years. The consequence on the coastal landscape is a series of terraces of abandoned shorelines, most prominent around the east coast firths and the Clyde. In addition, the rise of sea level enabled the coarser sands, gravels and pebbles to be carried inland to form the basis of the large forelands of the east coast, especially Buddon Ness and Culbin, and large bars such as Montrose. With the sea level fall, a progressively lower series of shingle and sand ridges was formed by the waves at the top of the beach and then abandoned; sand was blown over the ridges and sand dune systems began to form, aided by obstructions and periodic wetting by rain, especially prominent at Culbin, Forvie and Morrich More.
At present, many of the soft coasts are being eroded, perhaps as a result of increased storminess and lack of new materials being provided by the sea.
In the West Highlands and Islands a special type of sand system, 'the machair', has evolved. It is formed almost entirely of shell fragments derived from animals living in the deeper water offshore and swept shorewards by wave action which fragmented the shells. It lacks the traditional sand dune sequence - either it was never there or it has been blown away. These sand plains owe much to human agricultural activity for their continuance.