Yosemite National Park can be found in the Northern California, in the counties of Mariposa, Madera, and Tuolumne, and is located across the western side of the Sierra Nevada mountain range. It is a worldwide-known national park which is comprised of breathtaking landscapes including cliffs, rocky intrusions, waterfalls, and dales. These landscapes were formed over hundreds of millions of year to stand as they do today. In this paper, the history of the geological formation of the park and its contemporary geological features will be discussed.
The bedrock of Yosemite National Park, which consists mainly of granite, was mainly formed approximately 100 million years ago in a subduction zone (Glazner and Stock, 2013). Before the subduction, this area was a part of a continental margin; being in the shallow waters led to the formation of sedimentary rocks that were later subjected to metamorphism. At a certain point, the Farallon tectonic plate started going under the North American Plate (Waltham, 2012).
This process, together with the volcanic activity resulting from it, caused the formation of a number of volcanic islands located to the west from the North American coast. Later, these volcanic isles were again covered by magma because of the volcanic activity, which led to the beginning of the formation of the batholiths, intrusive igneous rocks, which later shaped the contemporary Sierra Nevada mountains. Also, a number of volcanic eruptions took place somewhat later, which became the cause of the territories located to the north of the contemporary Yosemite National Park being covered with magmatic rocks (Huber, 2007).
Approximately 10 million years ago tectonic movements started raising the mountains of the Sierra Nevada, which also resulted in the increased amounts of water currents going downwards and leading to the quicker formation of valleys and canyons. Nearly two million years ago, the pace of the Sierra Nevada’s rising increased further. It is also noteworthy that the granite mountains, due to being raised, started being influenced by higher pressure, which led to the spalling of the rocks. Also, landslides started taking place, which caused the cracks in the intrusive rocks (Huber, 2007).
It is stated that the formation of the Yosemite National Park’s landscape was also significantly influenced by glaciers. For instance, Yosemite Valley and some other well-known territories in the Sierra Nevada were formed due to the glacial erosion; glaciers moved downwards from mountains or peaks either by sliding or by deformation, and eroded the landscape by plucking or abrasion (Glazner and Stock, 2013).
The melting glaciers also very often led to the formation of moraines, which are nowadays often filled with water, thus forming lakes. Today, however, glaciers are few, and they occupy only the highest points of the area. It is stressed that approximately 500 glaciers were to be found in the Sierra Nevada in 1980, but even in 1999, this number was smaller, due to the effects of the global warming in particular (Kiver and Harris, 1999).
This geological history led to the formation of the contemporary Yosemite National Park’s geological characteristics. On the whole, it should be emphasized that a distinctive feature of the landscape of the Yosemite territories is a significant amount of bare, exposed granite (which also leads to the sparse vegetation in the area). It is also important to stress that the term “granite” is very general and includes various kinds of minerals such as diorites, granodiorites, tonalities; these are present inside the ten plutons which can be found in the walls of the Yosemite Valley (Waltham, 2012). The geological composition of the area is shown in Fig 1.
Another noteworthy feature of the Yosemite rocky formations is the continuous exfoliation of the rock masses. The exfoliation takes place due to the expansion of the rock resulting from the relief of the confining pressure. As a result of this, the curved joints of the Yosemite emerge; when erosion removes the exfoliated layers of the granite, new joints come into existence, and they become more and more rounded with time (Waltham, 2012).
As it was noted, glaciers and rivers also influenced the Yosemite’s landscape. Rivers led to the formation of valleys and canyons, and glaciers also added to their depth. Another effect of the presence of the glaciers is the polished granite on the slopes from which the glaciers were moving down (Glazner and Stock, 2013). Yosemite is also famous for its waterfalls (Cook, 2011); the movement of the water continues to shape the landscape of the national park nowadays (Waltham, 2012).
It also should be emphasized that erosion, which is also caused by rainfalls, earthquakes, and high levels of groundwater, can trigger rock slides and rock avalanches (Putirka, 2013); these can lead to fatalities and damage to property (Harp et al., 2008).
To sum up, it should be stressed that the history of the Yosemite’s landscape began nearly a hundred million years ago in a continental margin that was later raised due to subduction. Volcanic activity and tectonic movements led to the formation of the Sierra Nevada, and the Yosemite with it. Erosion and glaciers shaped numerous features of the landscape as it is known today. As a result, the area with its mountains, granite intrusions, and valleys was formed.
References
Cook, Robert B. “Geology Underfoot in Yosemite National Park by Allen F. Glazner and Greg M. Stock.” Rocks & Minerals 86.1 (2011): 71. MasterFILE Premier. Web.
Glazner, Allen F., and Greg M. Stock. Geology Underfoot in Yosemite National Park. Missoula, MT: Mountain Press Publishing Company, 2013. Print.
Harp, Edwin L., Mark E. Reid, Jonathan W. Godt, Jerome V. DeGraff, and Alan J. Gallegos. “Ferguson Rock Slide Buries California State Highway Near Yosemite National Park.” Landslides 5.3 (2008): 331-337. ProQuest. Web.
Huber, N. King. Geological Ramblings in Yosemite. Berkeley, CA: Heyday, 2007. Print.
Kiver, Eugene. P., and David V. Harris. Geology of U.S. Parklands. 5th ed. 1999. New York, NY: John Wiley & Sons. Print.
Putirka, Keith. D., ed. Geologic Excursions from Fresno, California, and the Central Valley: A Tour of California’s Iconic Geology. Boulder, CO: Geological Society of America, 2013. Print.
Waltham, Tony. “Yosemite–The Incomparable Valley.” Geology Today 28.1 (2012): 31-38. Academic Search Complete. Web.