3.1 Geology and sediments: setting boundary conditions for coasts
3.1.1 Coastal diversity: a heritage of geology and sediments
Coasts are extremely diverse in their morphology and sedimentary composition, and this diversity is largely explained by geology and by the sediments accumulating on coasts (Fig. 3.1). The geology determines the primary boundary condition within which the coast is formed and within which the processes of coastal evolution operate. The coastal boundary corresponds to the land-ocean interface, and involves a consideration of the overall tectonic framework and lithology. Embedded in these primary boundary conditions are sediment type and input. Three other important factors are the coastal space available for sediment to accumulate, called ‘accommodation space’, the topography, and the orientation of the coast, all of which reflect primary geological controls as well as the influence of sediment storage and redistribution in the coastal zone under the influence of coastal processes. Overall, therefore, coasts may range, in their morphology, from primary types hinged on the bedrock geology, to forms that reflect a large diversity of arrangement of sedimentary facies.