Introduction
Yosemite National Park is one of the significant nature reserves in the United States, located in the Sierra Nevada, California. Since 1984, the park has been under the protection of UNESCO. There are impressive granite rocks, picturesque valleys, meadows, transparent lakes and rivers, waterfalls, ancient giant sequoias, and a wide variety of animals and birds in this vast territory. However, the history of the park, which was created naturally, is of interest to explore. The formation of the park took millions of years, due to which various rocks were formed. The park’s geological history is of interest from the point of view of natural phenomena occurring in the territory that still form the park’s shape.
The History of the Park
Yosemite, in the language of the Apache Indians, means the name of the American black bear. The nature of the current territory of the park was revealed to European Americans in the middle of the 19th century during the gold rush. Nevertheless, this unique area arose thousands of years ago under the influence of a substantial continental glacier. About 540 million years ago, the national park’s territory was underwater near the continent’s coast. Four hundred million years ago, the Farallon tectonic plate began to go under the North American plate. As a result, volcanoes were formed, which formed the Nevadan mountain range, which gradually transformed into the Sierra Nevada.
Ten million years ago, the mountains on the territory began to rise, and having reached a certain height, they tilted, which is why the slopes on the west side were more gentle and steep on the east. As a result, the slope angle of the rivers flowing along the western slopes changed, directly involving the formation of valleys and gorges (Bloom & Deur, 2020). The process of mountain growth and erosion did not stop there, due to which gorges, canyons, rocks, and other forms of relief were formed.
Type of Rocks
At the moment, the geology of the territory is mainly characterized by granite rocks; however, it also includes some metamorphic rocks. The formation of the first rocks dates back to Precambrian time when the first territories of the current national park appeared on the continent of North America. Thus, many of the rocks that can still be observed in the park are granite formations that arose about 200 million years ago. These were volcanic films that had formed at least 5 miles deep. (Gutierezz & Bursztyn, 2020). However, over time, these rocks have been removed from the area due to erosion. This put the granite rock under much lower pressure and underwent a decline in layering and mass depletion.
Volcanic Activity and Fault Motion
Much of the northern region of Yosemite is covered in magma and igneous deposits. For 15 million years, the volcanoes of the Cascade Range have erupted, leading to the emergence of a large number of volcanic rocks in the park (Booth et al., 2020). Due to such eruptions, most of the lava flooded the Grand Canyon of Tuolumne. As a result of the slope of the Sierra block and the uplift of the mountains, the flow gradient in the territory increased to the western side. However, in spite of the fact that the rivers flowed faster, the tributaries retained their original speed, so their speed of clearing the valley was not significantly affected.
Another uplift occurred as a result of the development of significant faults on the eastern side of the territory. Erosion and shearing of tectonic plates have pushed granite rocks underground to the surface. This caused delamination (due to this, rounded granite domes can be observed in the park) and depletion of mass due to the formation of a large number of planes of joints of cracks in the plutons. The Sierra Nevada continues to grow within the park to this day. Today, the growth of some mountains exceeds the mowing rate due to erosion over a century period, resulting in a statistical increase in altitude. (Jenkins & Dietz, 2019). Rockfalls continue to reshape the canyon walls as rivers cut into the valley floor.
Geologic Conditions
The high peaks of the eastern and northern boundaries define the Tuolumne River drainage basin, which sets the meltwaters of the Lyell and Maclure glaciers. Tuolumne meanders through Tuolumne meadows and then flows through desolate canyons to the Hatch-Hatchi reservoir (Scoon, 2021). The channel of the river, bounded by the steep canyon walls, continues to cut vertically into the granite rock.
Tributaries flowing from high peaks along the park’s southeastern border merge to form the main trunk of the Merced River. The river meanders through Little Yosemite Canyon, cascades through Nevada and Vernal Falls, and flows into the Yosemite Valley. These rivers and tributaries, meandering along broad, U-shaped valleys cut by glaciers, form promontory bars, notches, floodplains, and terraces.
Conclusion
It took millions of years for the park to form, including phenomena such as glacier melting and faulting. When tectonic plates shifted, volcanoes were developed, which are still in the park. Thus, active faults and changes in shape also occur on the territory of the national park. The park’s geography is diverse and was formed by various natural disasters that happen in the modern environment of Yosemite.
References
Bloom, R. & Deur, D. (2020). Reframing native knowledge, co-managing native landscapes: ethnographic data and tribal engagement at Yosemite National Park. Land, 9(9), 335. Web.
Booth, D. B., Ross-Smith, K. Haddon, E. K., Dunne, T., Larsen, E. W., Roche, J. W., Stock, G. M. & Mahacek, V. (2020). Opportunities and challenges for restoration of the Merced River through Yosemite Valley, Yosemite National Park, USA. River Research and Application, 36(9), 1803-1816.
Gutierezz, J. A., & Bursztyn, N. (2020). The story of ice: Design of a virtual and augmented reality field frip through Yosemite National Park. IGI Global, 18(25), 1-16.
Jenkins, J., F., A., & Dietz, F. (2019). Moving beyond the frame: Geovisualization of landscape change along the southwestern edge of Yosemite National Park. Journal of Geovisualization and Spatial Analysis, 3(9), 17-23. Web.
Scoon, R.N. (2021) Yosemite National Park, California. The Geotraveller, 32(9), 37-50. Web.