Implications of Continental Drift to the Earth Sciences

Abstract

Quantitative geophysical evidence for the reality of continental drift was first obtained from the comparison of palaeomagnetic directions in igneous and sedimentary rocks from different continents. More recently Wegeners concept of continental drift has been beautifully complimented by the hypothesis of sea-floor spreading. Again the palaeomagnetism of the ocean floor has provided quantitative evidence for its occurrence. Thus the older qualitative arguments from the geological record, presented so imaginatively by Alfred Wegener, have been vindicated. In recent years we have seen a marked change in the climate of scientific opinion about the reality of major horizontal movements of parts of the Earths surface and, from palaeomagnetic and other geophysical studies, the positions of the continents in different geological periods and the evolution of the ocean basins are being determined. It is still not very clear how these movements take place in time and there is still considerable uncertainty about the precise relationships of different parts of the Earth's surface during the geological past. These developments have, however, essentially ended the long debate about whether or not the classical lines of geological evidence, palaeoclimatic, palaeontological distributions, global tectonic patterns and lithological relationships, support or refute drift. What is now scientifically significant is the study of the geological record in the light of the known horizontal displacements. This is of great potential importance to various other sciences involved in the study of our environment, e.g. biology, global meteorology. These two volumes are the proceedings of the April 1972 NATO Advanced Study Institute held in the University of Newcastle upon Tyne. They commence mainly with reviews of the objective evidence for the past position of the continents, i.e. the palaeomagnetism of continental and oceanic rocks. The palaeontological evidence is then examined to see how the creation of supercontinents and their fragmentation affects the mobility and rate of evolution of the biota on and around them. This data must also be examined carefully in order to delineate evidence which still appears inconsistent with current views of the past distribution of the continents to see if our presentviews need modification or whether such discrepancies can yield further information about our planet in the past, for example, the distribution of topographic, predatory or climatic barriers to the migration of terrestrial fauna. Similarly, the movement of continental fragments into different climatic belts obviously has an effect on their prevailing climate, but this movement, particularly the formation or fragmentation of supercontinents, must also hope a drastic effect on the climatic belts themselves.