CALCIUM CARBONATE The development of karst occurs whenever acidic water starts to break down the surface of bedrock near its cracks, or bedding planes. As the bedrock (like limestone or dolostone ) continues to break down, its cracks tend to get bigger. As time goes on, these fractures will become wider, and eventually, a drainage system of some sort may start to form underneath. If this underground drainage system does form, it will speed up the development of karst arrangements there. This increase in rate of karst feature development will be due to the fact that more water will be able to flow through the region. The carbonic acid that causes these features is formed as rain passes through the atmosphere picking up carbon dioxide(CO 2 ), which dissolves in the water. Once the rain reaches the ground, it may pass through soil that can provide much more CO 2 to form a weak carbonic acid solution, which dissolves calcium carbonate . In particular and very rare conditions such as encountered in the past in Lechuguilla Cave in New Mexico (and more recently in the Frasassi Caves in Italy), other mechanisms may also play a role. The oxidation of sulfides leading to the formation ofsulfuric acid can also be one of the corrosion factors in karst formation. As oxygen (O 2 )-rich surface waters seep into deep anoxic karst systems, it brings oxygen which reacts with sulfide present in the system ( pyrite or H 2 S) to form sulfuric acid (H2 SO 4 ). Sulfuric acid then reacts with calcium carbonate causing an increased erosion within the limestone formation. This reaction chain forms gypsum .
Posted on: Mon, 05 Jan 2015 04:31:09 +0000
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