the part of the earth is crust called the british isles seem eternal and unchanging in its shape. but this only when it is viewed against the time scale of human history , which measured time in hundreds or at the most thousands of years. Viewed against a geological time-scale, where the years are measured in their thousands of millions the surface of Britain has been in continual movement alternately collapsing erupting and heaving itself above and below the sea under the stresses set up in the bowels of the earth