Yosemite National Park

Site information

• Official name: Yosemite National Park
• Location: California, United States
• Type: Natural
• Year of inscription: 1984

Long acclaimed for its exceptional scenery, Yosemite was the first parkland in the United States to be set aside for the natural beauty it contained. The Yosemite Grant was deeded to the state of California by an Act of Congress in 1864, a special reserve to be protected for all time for public recreation and use.

Yosemite was transferred back to the federal government as a national park in 1890. The US Army held the responsibility of patrolling the new parklands from 1891 to 1913. Many of these first park rangers were buffalo soldiers, members of all–African American regiments formed after the Civil War and sent west.

Yosemite National Park is also noted for its wilderness values. Almost 95 percent of the park is designated wilderness. Due to the varied topography, nearly all the different environments located within the Sierra Nevada can be found here. Yosemite boasts a diverse palette of flora and fauna within its 1,169 square miles (3028 sq. km). There are fifteen hundred species of plants in Yosemite, 160 considered rare. Thirty-seven species of vertebrates within the park borders have either state or federal special status.

One group of special concern is amphibians. Although many species are in decline, one species, the Sierra Nevada yellow-legged frog (Rana sierrae), is one of the world's most critically endangered amphibians. Once the most common frog in the Sierras, the population has declined nearly 95 percent in less than twenty years. The introduction of nonnative trout and the emergence of an invasive chytrid fungus are the major causes for this decline. Contributing factors include ozone pollution, habitat fragmentation, and climate change.

Geologic History

Yosemite National Park is the result glaciers grinding down granite. The Sierra Nevada in Yosemite was formed by plate tectonics. The Farallon Plate was subducted under the North American plate between 120 million and 185 million years ago, during the Jurassic and Cretaceous periods of earth history. As the plate descended into the mantle, the melting rock began to rise and form magma chambers that never broke the surface, creating intrusive igneous rocks, primarily granite.

There is a complexity to Yosemite's granites that is not apparent at first glance. There are thirty-five individually defined magma chambers (plutons) in Yosemite. There were several different upwellings, magma events that happened during the subduction. A group of plutons that occur during the same event are known as intrusive suites. There are seven intrusive suites in Yosemite. The Sierra Nevada is the result of the consolidation of all these different plutons into one massive body of rock (batholith). Approximately twenty-five million years ago, this batholith, buried deep underground, broke free along a series of related faults on the east and was uplifted and tilted west. The uplift and tilting along the fault continues to this day.

Glaciers came to the mountains of Yosemite between two and three million years ago. Ice sculpted the rock into distinctive features. Granite is a very hard rock and not easy for the ice to carve. However, not all granite is created equal. As the crystals in the plutons formed and cooled, the rock contracted, forming parallel fractures (joints). Due to the rate of cooling and the ratio of different minerals in the rock, some granites are more prone to forming joints than others. The cracks cause these rocks to erode faster and easier than granite with fewer or no joints.

Although nearly all the glaciers are gone, erosion still shapes Yosemite's landscape today. Yosemite has more rockfall than any other national park in the United States. One of the dynamic forces that cause this rockfall is exfoliation, the peeling away of layers of rock like the layers of an onion. Since this rock crystallized underground at extreme pressures, the release of pressure as the rock came to the surface caused it to expand outward, forming sheets, or layers. Freeze/thaw cycles allow water to expand between the layers. Sheeting rounds the rocks, forming the distinctive domes Yosemite is famous for. Seismic activity is another cause of rockfall.

Another way erosion is shaping the landscape is through floods and debris flows. Heavy winter rains may melt the snowpack and inundate the already saturated ground. This type of winter flood is projected to become more frequent in the future as a result of climate change.

The National Park Service is working to maintain Yosemite's distinctive features through active management programs, such as vegetation removal to preserve the viewscape and visitor education. In 2016, the National Park Service accepted the donation of the Ackerson Meadow. This was the largest addition to Yosemite since the mid-twentieth century. In 2018, several sections of the park were temporarily closed due to the Ferguson Fire, a large wildfire on the park's western side.

Significance

Yosemite has the greatest concentration of granite domes in the world. The complexity of the granites and their high level of polishing make Yosemite an excellent place to study the internal intricacy of a batholith.

Yosemite is one of the world's ultimate rock climbing regions. The strength of the granite, cracks and holds formed by the slow crystallization of the rock, and some of the largest exposed granite monoliths in the world have created a haven for rock climbers.

The scenery of Yosemite National Park has inspired millions and is integral to the creation of the modern environmental movement. One of those inspired by Yosemite was John Muir. a naturalist, writer, and wilderness activist, Muir is considered by many to be the father of environmentalism. His writings in the 1870s inspired the popular interest that convinced Congress to protect Yosemite. He lobbied successfully in 1890 to make Yosemite a national park. In 1892, Muir founded the Sierra Club. As its president, he was a major force in convincing Congress to create the Sequoia and Grand Canyon National Parks.

Another man whose life is deeply connected to Yosemite's superb scenery is Ansel Adams. Adams is one of the most respected photographers of all time. His Zone System defined black and white photography during the film era. An advocate for the preservation of wild places, Adams's photography was essential to the passing of the Wilderness Act in 1960.

Bibliography

Glazner, Allen F., and Greg Stock. Geology Underfoot in Yosemite National Park. Mountain Press Publications, 2010.

Graham, J. Yosemite National Park Geologic Resources Inventory Report. National Park Service, US Department of the Interior, 2012.

Huber, N. King. The Geologic Story of Yosemite National Park. US Geological Survey, 1987.

Muir, John. The Yosemite. Project Gutenberg, 2015.

Ogden, Kate Nearpass. Yosemite. Reaktion Books, 2015.

Salcedo, Tracy. Historic Yosemite National Park Stories. Lyons Press, 2016.

"Yosemite." National Park Service, 13 Nov. 2024, www.nps.gov/yose/index.htm. Accessed 8 Dec. 2024.