Karst

Karst is a topography formed from a dissolution of soluble rocks such(a) as limestone, dolomite, and gypsum. it is characterized by underground drainage systems with sinkholes together with caves. It has also been documented for more weathering-resistant rocks, such(a) as quartzite, given the modification conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is quoted perhaps by debris or confined by one or more superimposed non-soluble rock strata, distinctive karst atttributes may occur only at subsurface levels and can be completely missing above ground.

The examine of paleokarst buried karst in the stratigraphic column is important in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in carbonate rock, and much of this is found in porous karst systems.

Development

Karst is nearly strongly developed in dense carbonate rock, such as limestone, that is thinly bedded and highly fractured. Karst is not typically living developed in chalk, because chalk is highly porous rather than dense, so the flow of groundwater is not concentrated along fractures. Karst is also almost strongly developed where the water table is relatively low, such as in uplands with entrenched valleys, and where rainfall is moderate to heavy. This contributes to rapid downward movement of groundwater, which promotes dissolution of the bedrock, whereas standing groundwater becomes saturated with carbonate minerals and ceases to dissolve the bedrock.

The Earth's atmosphere picking up carbon dioxide CO₂, which readily dissolves in the water. one time the rain reaches the ground, it may pass through soil that helps additional CO₂ delivered by soil respiration. Some of the dissolved carbon dioxide reacts with the water to hit a weak carbonic acid solution, which dissolves calcium carbonate. The primary reaction sequence in limestone dissolution is the following:

In very rare conditions, oxidation can play a role. Oxidation played a major role in the profile of ancient Lechuguilla Cave in the US state of New Mexico and is presently active in the Frasassi Caves of Italy. The oxidation of sulfides main to the positioning of sulfuric acid can also be one of the corrosion factors in karst formation. As oxygen O₂-rich surface waters seep into deep anoxic karst systems, they bring oxygen, which reacts with sulfide featured in the system pyrite or hydrogen sulfide to realize sulfuric acid H₂SO₄. Sulfuric acid then reacts with calcium carbonate, causing increased erosion within the limestone formation. This chain of reactions is:

This reaction group forms gypsum.