Rock Outcropping

Rock formations of all kinds are important parts of the landscape, but can often be overlooked as the result of people not understanding their rather remarkable nature and the history of their formations. Identification of rock formations and a knowledge of their history is an important part of earth science education. This paper will seek to give a general description of the rock outcropping presented in the photographs, and go on to talk about limestone rock in general, as well as touching on the possibility of fossil presence in the outcropping.


The outcropping in the photographs presented is long and is striated; its surface is a combination of white and pale gray and it appears somewhat smooth and weathered. It also appears to be formed of multiple, somewhat thin layers of rock. It is covered with a layer of vegetation (most coniferous to judge from the photos of the flora and by the large mat of pine needs at the base of the outcropping). The rock appears to have been cut to make way for development, to judge from the manicured strip of grass at its base and is immediately next to some sort of developed area, going by the closeness of the parking lot in one of the pictures .


Most likely this outcropping is made out of limestone, which is a common sedimentary rock. It is formed largely of calcite, a form of calcium carbonate. Limestone occurs when detritus such as the skeletons and shells of small marine mammals, along with clay, silt, sand, and animal waste, settle in layers at the bottom of warm, shallows seas and eventually lithify. Because of the nature of its formation, with layer upon layer of detritus building up as the limestone forms, it is considered to be a sedimentary rock and this would account for the layers clearly visible in the outcropping from the photograph. The white strata in the outcropping could well be calcium carbonate; limestone, though, because of the presence of various minerals, silts and clays, can have a wide range of color.


There is no visible evidence of fossils to be seen in this photograph, but the presence of fossils in limestone is very likely, since limestone is formed from the calcium carbonate to be found in the skeletons and shells of sea creatures like clams, brachiopods, bryozoa, crinoids and corals; silica-rich organisms like diatoms may also be present. Some types of limestone, called coquina, is brittle, poorly cemented masses of broken shell debris, and another limestone, called fossiliferous limestone, contains abundant fossils. However, this does not seem to be the case with the limestone photograph presented in this picture.


To conclude, this outcropping does appear to be of limestone, formed by layers of skeletons and shells of marine animals which lithified over time. To judge from the presence of the limestone it might be possible to speculate that this area was once covered by shallow, warm seas in the distant past, where much limestone is formed. It is also possible to speculate upon the possibility of the presence of fossils in this rock, remnants of the marine animals from whose skeletons and shells the limestone eventually was made.