Gypsum is about 10-20 times more soluble in pure water than limestone is in the presence of CO2, resulting in extremely rapid cave development. In addition, several chemical and physical factors may enhance or renew gypsum dissolution. Quantitative estimates of the effect of these factors are sparse. The goal of this study is to determine the mechanisms and rates of gypsum cave development in Oklahoma, where gypsum occurs in 25% of the state. The proposed study will provide much needed information on gypsum karst of Oklahoma, with potential implications for gypsum karst elsewhere in the USA. The rapid cave development in gypsum rock poses many problems to the infrastructure and land use in areas where gypsum is found at the surface or in the subsurface; e.g. loss of farm or industrial equipment when the land surface gives way under its weight, loss of livestock that has fallen into sinkholes, collapse of sections of roads as a result of the retreat of cave entrances. Determining the rate of this development would greatly help urban planning and land use projects by supplying a better understanding of the risks of karst hazards in the areas involved. Gypsum karst, just like carbonate karst, is also very susceptible to environmental impact problems in general and water pollution in particular, due to rapid infiltration and limited filtration of pollutants in the relatively large solutional conduits. Research on cave development and karst hazards has been focussed in carbonate rock mainly and less gypsum rock, undoubtably due to the fact that gypsum karst is much less common and accessible than carbonate karst. This study will attempt to identify and quantify the different dissolutional and mechanical cave development processes at work in gypsum caves in western Oklahoma, i.e. 1. Dissolution by flowing and standing water; 2. Effect of the presence of other salts on dissolution; 3. Condensation corrosion: dissolution by aggressive condensation water in air filled passages; 4. Microbial activity: anaerobic reduction of sulphates in the presence of organic matter; 5. De-dolomitization of intercalated dolomite layers; 6. Collapse. The study will involve digital mapping, cave microclimatological studies, water chemistry and condensation corrosion to determine erosion and dissolution rates.