Good Essay On The Formation Of Mammoth Cave In Kentucky
Cave formation requires some geological and hydrological factors. According to Kleber and Kentucky Bicentennial Commission (1992), the first requirement for cave formation is a vast region of land that is underlain by a rock that dissolves in water mainly limestone. The second requirement for the formation of the caves relates to the position and alignment of the limestone rock. There are suggestions from Kleber et al. (1992) that the rock should be positioned in such a way that water can easily seep through the rock to its base. The water soluble rock should be covered by an erosion resistant rock. The presence of adequate precipitation is another important requirement for the formation of a cave. Kentucky’s setting meets almost all the conditions and requirements for the development of caves.
Mammoth cave is the longest cave in the world found in a hill that is mainly made of limestone and sandstone rocks in south west Kentucky. The existence of limestone rock in the region among other factors formed a basis for the cave formation (Packard & Putnam (1872). According to Graf, (2004), the geology of the area occupied by the mammoth cave is ideal for the formation of a cave and that is the main characteristic of the region that led to the formation mammoth caves.
According to Graf (2004), the mammoth area was long ago covered by sea water. The small marine animals which dwelled in the sea left skeletons when they died. After a long period of time, these skeletons compacted to form limestone rock (calcium carbonate).When the sea dried up, a river dumped some sand on the limestone rock that was formed. The sand became sandstone rock over time and covered the limestone rock
The presence of limestone rock made it possible for the formation of the cave. According to Wallace, (2003) the formation of the cave begun as the rain water picked carbon (IV) oxide from the atmosphere and seeped through the soil. Burnham (2003) says that the seepage of water into the ground also picked some carbon (IV) oxide from the soil. When this water reacted with the picked carbon (IV) oxide, weak carbonic acid was formed. The weak carbonic acid formed entered the cracks of the limestone rock and reacted with the limestone rock (calcium carbonate). The reaction between limestone rock and weak carbonic acid led to the formation of water, carbon (IV) oxide and some calcium chloride which is a water soluble substance. The formed calcium chloride dissolved in water and was carried away by water leaving caves behind.
Sand and shale, which are not soluble in water, were left behind after the dissolution of limestone. These rocks facilitated formation of caves because of their resistance to erosion. This is because, these resistant rocks formed a cover that prevented the land from collapsing after the interior limestone rock had been eaten away by the weak carbonic acid. Otherwise, caves could have disappeared because erosion could have lowered the surface were it not for the hardness of the cap rock (Wallace, 2003).
Water, which is the main agent of cave formation, contributed a lot to the development of mammoth caves. According to Wallace, (2003), water that was flowing on the surface mainly flowed into the vertical cracks. With time, these cracks developed to form pit like shafts. Some water also flowed horizontally on the bedding planes of the rocks. According to Kleber et al. (1992), water seeping into the ground filled the joints and bedding planes first. The small and narrow fissures were enlarged by the water that flowed through them slowly with time. Enlargement of this fissures was due to erosion and dissolution of limestone rock in water. After a long period of time, the joints and fissures developed to form large caves (Klass, 2005).
The amount of rainfall received in the Kentucky region is adequate for the formation of caves. Since water is the main agent in the formation of the weak carbonic acid, presence of high rainfall increased the amount of the carbonic acid formed. This high rainfall and the humid condition in the region also promoted the growth of vegetation (Klass, 2005). The decay of the vegetation produced some organic acids and supplied the soil with carbon (IV) oxide gas. Carbon (IV) oxide and the organic acids produced by decaying vegetation increased the acidity of the underground water. The acidic water reacted with the limestone rock along the joints and produced soluble calcium chloride which was carried away by the underground water leaving caves behind. (Kleber et al., 1992).
The presence of pure limestone, insoluble and water resistant cap rock, good development and spacing of joints and availability of well aligned bedding planes facilitated the formation of the caves. According to Kleber et al. (1992), the limestone in the Kentucky region is 95 percent pure (calcium carbonate). The bedding planes in the region had wider spacing. This made it possible for water to enlarge them by dissolving the adjacent rocks. The limestone is protected by an erosion resistant sandstone. The sandstone rock is made of cemented quartz sand that is resistant to erosion. The regions that are away from the river had been eroded leaving some depressions behind. These depressions formed a seepage way through which water passed to the ground during precipitation. This water eroded the limestone rock and dissolved some due to its acidity. Leaving behind large openings which developed with time to form larger caves.
Another way that the caves were formed is through the aid of the disappearing rivers and streams. During the initial development of the caves, the passages are believed to have been filled with water and with time, they enlarged to all directions. Fall in the water table led to the formation of another layer of passage similar to canyons by the small waterfalls that resulted from falling down of the water table. These canyon passages finally extended and joined the older passages leading to the formation of a large cave (White & Culver, 2012).
The green river valley according to White et al., (2012) also facilitated the formation of the mammoth caves because it slowly deepened down throughout the ice age. As it deepened down with time, different levels of the caves formed with respect to the new depth of the river. This led to the formation of different levels of the caves from top to the floor of the river (White et al., 2012).
The mammoth cave has some unique characteristics.it is the longest in the world because during its formation the multilevel structure of caves that resulted from deepening of the green river kept on collapsing. The resistant and impermeable cap rock protects the seepages from dripping water making them dry (McManamon, Cordell, Lightfoot & Milner, 2009).
Mammoth caves have some other inbuilt features that resulted from the formation of the cave. Such features include speleothems, stalactites, stalagmites, and gypsum. Stalactites refer to speleothems, which are formed by dripping of water containing calcium carbonate into an air-filled passage. This leaves deposits of precipitated calcium carbonate that did not fully react with water hanging from the ceiling of the cave. A stalagmite grows from the ground of the passage as the water drips from the ceiling of the passage making a protrusion from the floor of the passage. Gypsum is another mineral deposits that are found in dry parts of a cave (Graf, 2004).
Burnham, B. (2003). Mammoth Cave: The world's longest cave system. New York: Rosen Pub. Groups PowerKids Press.
Graf, M. (2004). Mammoth Cave National Park. Mankato, Minn: Bridgestone Books.
Klass, R. (2005). Mammoth Cave National Park: Reflections. Lexington, Ky: University Press of Kentucky.
Kleber, J. E., & Kentucky Bicentennial Commission. (1992). The Kentucky encyclopedia.
McManamon, F. P., Cordell, L. S., Lightfoot, K. G., & Milner, G. R. (2009). Archaeology in America: An encyclopedia. Westport, Conn: Greenwood Press.
Wallace, D. R. (2003). Mammoth Cave: Mammoth Cave National Park, Kentucky. Washington, D.C: Division of Publications, Harpers Ferry Center, National Park Service, U.S. Dept. of the Interior.
White, W. B., & Culver, D. C. (2012). Encyclopedia of caves. Waltham, MA: Academic Press.