2.2.2: Continental 'drift'

Figure 2.1: Continental drift is the movement of the earth’s continents relative to each other. After Wegener (1929).

Around 200 million years ago the world’s continents formed a primordial super-continent, called Pangaea (Greek for ‘all earth’). The continuity of geologic features across the now widely separated continents supports this idea. The continental land masses that formed Pangaea gradually drifted from their original positions (see Fig. 2.1). They reached intermediate locations 135 million years ago, between the Jurassic and Cretaceous Periods. After almost 200 million years, the continents reached their present positions, though we can observe that they are still drifting. Nowadays, it is known that even before the formation of Pangaea, the continents were already drifting; there have been a number of cycles of continental break-up, drift, and collision, each lasting a few hundred million years.

The hypothesis that continents ‘drift’ was fully developed by Wegener in the beginning of the 20^th century (Wegener, 1912, 1929). However, it was not until the development of the theory of plate tectonics in the 1960s that a sufficient geological explanation of that movement was found (see Sect. 2.3.1). This process of plate tectonics has had an enormous impact on the formation of coastlines and determines the broadest features of the coast. Important inherited aspects are the continental shelf configuration (mainly width and slope of the shelf) and the lithology (see Sects. 2.3.2 and 2.3.3).