Introduction
Missouri is best known for its numerous scenic beauties. One of the beauties is the abundant caves found in the region. The region has more than 5,500 caves with most of the caves bearing other scenic features inside them. Onondaga cave State park is one of the state parks in Missouri situated in Leasburg. It was instituted in 1982 and since then, it has been offering numerous recreational services to visitors. Fishing, hiking, and swimming comprise some of the recreational activities found in this park. For a long period, numerous natural processes took place in the park leading to changes in its geological structure that make it attractive to tourists (Missouri department of natural resources, 2008, para. 1). This paper aims at giving a brief history of the geology of the cave found in the park.
The geological history of the cave
About a billion years ago, the region was faced with numerous volcanic eruptions. After the eruptions, volcanic ash cooled forming the current felsites, basalts, and rhyolites materials found on the surface of the cave (Missouri department of natural resources, 2008, para. 2). Due to the eruption, there was the emergence of water vapor which later condensed and collected into shallow seas. As the vapor collected into seas, there was the deposition of dolomites, shale, and sandstones.
Scientists believe that Ozarks was raised about four times above sea level to its current altitude. At some stage in these processes, there was the development of sedimentary rocks as well as the set down of materials collected by water at the bottom of the sea. For more than four hundred years, the area has been dry leading to most of the underground rocks being exposed while others have already been eroded. The region that was once raised above sea level has been subsided several feet below the ground through soil erosion. Most of the rocks on the surface of the cave are composed of Gasconade dolomite which is rich in gastropod fossils (Missouri department of natural resources, 2008, para. 3-6).
The roof of the cave is mainly made of these rocks with part of its surface is made of dolomite. The dolomite is found not to contain any fogies. However, they have traces of calcium silicate and quartz in form of algae reefs which leads to the formation of stromatolites fossils. Outside the cave, there are loosely held Rubidoux sandstones. Dolomite sand and quarts are found to be the only minerals found in the shiny surfaces of dolomite rocks. Most of the speleothems on the paling of the caves are composed of the youngest rocks. This is because they continuously trickle and form as time goes on.
There is no clear estimate of the time when the cave was formed. This is because there are no materials in the cave that dates back since its formation. There is no definite method of dating the cave formation as people wonder when the actual dating is supposed to begin. Conducting a carbon dating test on some of the materials found in the cave such as speleothems gives only the period when they were formed and not the date when the cave was formed (Unklesbay & Vineyard, 1992, p. 126).
Due to the Leasburg fault, the forces on both sides of the rocks in the region led to the rocks cracking. As the water flow along the rocks, it looked for the weakest portions of the rocks which were in these cracks. This led to the formation of the caves as the weak rocks were eroded by water. It is believed that the cave was carved out from the weak parts of the underlying rocks as well as the joints by underground streams. Fractures resulting from Leasburg Fault led to the rocks becoming weaker thus making it possible for the cave to be formed. Deposits of red clay and chert from dolomite were observed on the floor of the caves during the periods when there was slow flow.
As the land continued wearing off, the water table went down making water and air reach the cave. This water eventually became the cave stream. As the streams flow along the surface of the cave, they started eroding the red clay and chert. Presence of air in the cave coupled with water led to the growth of speleothems (Weaver, 2008, p. 54). As the water table in the cave dropped, more of the passages that had been developed in the cave got filled with air. The release of carbon dioxide from the underground water into the caves led to the alteration of the chemical balance. Consequently, the cave started being occupied by cave deposits that led to the formation of aragonite precipitates.
It is believed that there existed a sea in the area where the cave is currently situated. Deposits from the sealed to the formation of sedimentary rock (Weaver, 1992, p. 87). The combination of water sediments collected from land, dead organisms as well as other precipitates from seawater condensed to form sedimentary rocks after being subjected to extreme temperature and pressure. Sedimentary rock comprising of dolomite resulted after limestone in the region reacted with water rich in magnesium. Availability of heat and pressure led to the chemical composition of the underlying rock changing from limestone to dolomite.
The rise in height of the seafloor led to the sea retreating leaving the area dry. Exposure of the rock to the sun together with an external force led to it cracking. The various layers of the rock became disjointed.
As water flowed along the cave’s walls, it deposited some calcite minerals along it forming flowstones. These were also formed on the floor of the caves along the streams. As the water flow along the stream, it released carbon dioxide leading to calcite being deposited as precipitates. Eventually, the calcite deposits led to water collecting behind them forming rimstone dams (Unklesbay & Vineyard, 1992, pp. 136-145).
Conclusion
Onondaga cave State park is one of the state parks in Missouri. It is located in Leasburg and was established in 1982. The park is characterized by caves that resulted from weathering of dolomite rocks. The geological history of the park indicates that the region was initially occupied by seas which led to the deposition of sediments. The sediments were then subjected to pressure and heat resulting in the formation of dolomite rocks.
The uplifting of Ozarks led to the seas retreating exposing the dolomite rocks. Leasburg fault coupled with heat and other external forces made the rock crack. As the rock continuously became weak, water-eroded it leading to the formation of caves. The dolomite rock found in these caves is said to containing elements of stromatolites fossils. This is an algae reef rich in quartz and calcium silicate. As the water flow along the walls of the caves, it led to the deposition of calcite minerals resulting in flowstones.
Reference List
Missouri department of natural resources. (2008). Geological history of Onondaga cave. Web.
Unklesbay, A. G. & Vineyard, J. D. (1992). Missouri geology: three billion years of volcanoes, seas, sediments, and erosion. Missouri: University of Missouri Press.
Weaver, D. H. (1992). The wilderness underground: caves of the Ozark Plateau. Missouri: University of Missouri Press.
Weaver, D. H. (2008). Missouri caves in history and legend. Missouri: University of Missouri Press.