|
Foreword
GEOLOGY,CLIMATE,HYDROLOGY AND KARST FORMATION IGCP PROJECT 299 Karst of various kinds covers over 15% of the earth's surface. Allareas of karst are characterized by underground drainage and disorientation of the normal surface drainage network. Normal rivers are replaced by sinking streams and closed depressions feed into underground conduits. Even in high mountain and high rainfall intensity areas, where surface streams and gullies initiate the relief, eventually the influence of the soluble rocks takes over and the surface drainage is disorganized. Accompanying this disorganization, there is a re-organization of the underground hydrology and drainage; this re-constitution of the underground network of water channels produces the surface and subsurface karst landforms. Because of the complexities of rock control and differences in rock solubilities, tectonics, topography, climatic and ecological factors, the re-organization of the hydrology takes place in various ways, producing very different suites of surface and sub-surface landforms. But all are related to the transference of the drainage into an undergroud network--called by Ford and Williams ---the "karst plumbing"(reference 1). Before the development of the karst plumbing, karst landforms and caves cannot exist, and the karst system does not exist. The setting up of IGCP project 299, will enable the complexities ofthe features affecting the break-down of the surface hydrology and it's reconstitution into an underground network, to be analysed; and the ways in which these changes affect the evolution of surface and subsurface landforms, can be deduced. Thus the great areal differentiation between the landforms in karst can be explained and eventually modeled. Because the hydrology of karst is related to the amount and type of rainfall in an area, karst is profoundly affected by climate and climatic change. Thus the study of karst is an important part of the world--wide study of climatic change. Caves and closed depressions accumulate all types of sediments and act like geological dustbins--where both inorganicand biological sediments remain over long geological periods and are not washed away. The driving force of the hydrological network, though partly conditioned by tectonics and relief, is determined by the hydrological processes involved which are themselves controlled by climate. Furthermore, because of the soluble nature of the karst rocks themselves, karst soils are thin and the vegetation is affected by small climatic changes and by changes in human land use. Thus karst is particularly environmentally sensitive both from the physical and biological point of view and also from the point of view of human impact. Karst therefore reflects the world-wide environmental changes associated with other climatic and geological studies, such as in sea-level change and in snow and glaciological budgets. Part of the IGCP 299 will be to correlate such environmental issues; little correlation has so far been done. Though karst is sensitive to environmental change, because of the relative lack of surface drainage, many karst landforms are old and remain in the landscape a long time. There is a great deal of inheritance of both climatic and palaeogeographical regimes in the surface and underground landforms and their accompanying sediments. This might be called the karst paradox. But there is an enormous potential in the reconstruction of former palaeo-geographical and palaeo-climatic conditions from investigations into the landforms and from studies of cave and closed depression sediments. Among the developments I see in the next 5 years are the following: (1).An exact description of many karst areas rever previously studied; there are many areas where we have no exact data. No observation is irrelevant and each can be incorporated into the data set. In this context there are many isomorphic landforms similar to those in the karst--sandstone "stone forests" and karren on basalts for example, which are worth attention. (2). The development of more precise models from both laboratory and field studies for specific hydrological contexts and for specific karst landforms. Such models will be enhanced by improved computer techniques. (3).New techniques of measurment and analysis both in the field and in the laboratory are developing all the time. (for instance in pH measurement and CO2 measurments). Karst workers must use these wherever possible--to improve our knowledge of Karst geochemistry and kinetics and to refine our examination of sediments and dating techniques. Thus new developments in S.E.M., in laser granulometry, in isotopic and palaeomegnetic measurments, must be applied wherever possible in karst studies; also the newly developing work in electron spin resonance(E.S.R) needs our attention. (4).A greater appreciation of the complexities and inter-relationships of karst evolution is needed. Karst development is dependent upon a complex of processes. Gone are the days when we sought to characterize karst areas solely in terms of either climate, or relief, or tectonics or lithology or hydrology; we now seek to delineate karst in terms of a complex of inter--acting forces. Subtle changes in these forces and processes can radically change the karst, and change the system. (5).Evidences of climatic change, both modern and in the geological record are abundant in karst. As we increase our knowledge of environmental change, we need to monitor closely its impact upon present karst processes and landforms; and as karst provides evidence of former environmental change, we need to reconstruct former palaeo-geographical periods. (6).As mankind spreads more over the earth, we must become further aware of the problems caused by the human use of karst resources, particularly those caused by the pollution of karst water, by land subsidence, and by the degradation of the cave environment caused by the growth of tourism. The purpose of this foreword is to encourage all papers and reports related to the Project to be sent to Professor Yuan Dao-Xian as soon as possible. The inaugural meeting is to be in Antalya, Turkey, Oct. 7-16,1990, when the working programme of this project will be discussed and defined. We owe much to the energy and far-sighted drive of Prof. Yuan Dao-Xian in getting the project underway. The timing of the IGCP Project 299 could not be better. Over the past few years, there has been increasing collaboration between Karst workers, which can now be re-inforced. We should take advantage of the opportunities afforded by the project to correlate the principles underlying the geological, climatic and hydrological processes which determine the surface and subsurface forms and to define their regularities and differences. So that by the end of the project in five years time, we should have a much better data-base, suitable for use in more sophisticated modeling programmes; these should help us predict future karst processes and assist in the pretection of the fragile and sensitive karst environment. The IGCP 299 project should transform the somewhat singular and isolated nature of karst studies into a modern world-wide science with its own laws and principles which can be modeled and predicted. Suggestion and ideas for the project will be welcomed by Prof. Yuan Dao-Xian in Guilin. It is no accident that the driving force for this project has originated in the largest contiguous area of karst in the world, South China.
Reference
|
|
Comments and suggestions to Webmaster, |