THE RESEARCH FRONTIER AND BEYOND - GRANITIC TERRAINS

Investigations of granite forms and landscapes over the past two centu ries suggest that many features, major and minor, are shaped by fractu re-controlled subsurface weathering, and particularly moisture-driven alteration: in other words etch forms are especially well represented in granitic terrains. Commonly referred to as two stage forms, many ar e in reality multistage in origin, for the structural contrasts exploi ted by weathering and erosion that are essential to the mechanism orig inated as magmatic, thermal or tectonic events in the distant geologic al past. Fracture patterns are critical to landform and landscape deve lopment in granitic terrains, but other structural factors also come i nto play. Location with respect to water table and moisture contact ar e also important. Once exposed and comparatively dry, granite forms te nd to stability; they are developed and diversified, and many are grad ually destroyed as new, epigene, forms evolve, but many granite forms persist over long ages. Reinforcement effects frequently play a part i n landform development. Several granite forms are convergent, i.e. fea tures of similar morphology evolve under the influence of different pr ocesses, frequently in contrasted environments. On the other hand many landforms considered to be typical of granitic terrains are also deve loped in bedrock that is petrologically different but physically simil ar to granite; and in particular is subdivided by fractures of similar pattern and density. To date, most of the general statements concerni ng the evolution of granitic terrains have been based in work in the t ropics but other climatic settings, and notably those of cold lands, a re now yielding significant results.Future research will extend and de velop these avenues, but biotic factors, and particularly the role of bacteria, in such areas as weathering, will take on a new importance. Structural variations inherited from the magmatic, thermal and tectoni c events to which granite bodies have been subjected will be more and more appreciated as offering explanations for a wide range of granite forms, major and minor, ancient and recent. In particular, investigati ons of rock strain, including gravitational loading, at a variety of s cales, and especially as it influences fracture patterns and susceptib ility to weathering, will assume a prime importance in the explanation of granitic landforms and landscapes. Finally, there are genuine hope s that the close dating of surfaces and weathering events will allow s tructural and process studies to be placed in their chronological cont exts. New techniques and observations will prove important to advances in the understanding of granitic forms, but, as in other areas of geo morphological endeavour, fresh perceptions, different linkages and new ideas are critical.