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Roger Weller, geology instructor

wellerr@cochise.edu

Yosemite
by Dawnielle Burnell
Physical Geology
Fall 2009  

                                          Yosemite National Park
 

Picture taken by Dawnielle Burnell

          Yosemite National Park is known as one of the most beautiful parks in America. It is one of the three most well known parks in the national park system after Yellowstone and the Grand Canyon, and is one of the most popular. With its popularity, Yosemite was visited by over four million people in 1994. With Yosemite’s history of how it came to be, the story behind its geology that have created the beautiful foundations, keeps the rivers running, and the waterfalls flowing, and the main attractions that bring people from all over the world to continuously visit this beautiful national park. Attractions such as Half Dome, El Capitan, and the Yosemite falls, which all are located in the Yosemite Valley area, keeps this park as one of the most visited in the world.

A brief history: Years ago before Yosemite became a national park; American Indians inhabited the valley region around six thousand years ago. Around the time Euro-Americans came to Yosemite in the mid nineteenth century, the valley was given the name “Ahwahnee,” which loosely translates into “Place of a Gaping Mouth” after that the Indians called themselves “Ahwahneechee.” From there they have lived harvesting black oak acorns, hunted and fished, and traded items native to Yosemite Valley with the Mono Lake Palute people. Word of Yosemite's beauty spread. In 1855, the first party of tourists came. Nine years later, Yosemite Valley was granted to the state as the country's first public preserve. Since then, many of the staff has worked hard keeping Yosemite's natural beauty safe and protected so future generations can enjoy its cultural beauty and treasures.

Yosemite's Geology: Yosemite's geology is made of granite rocks and remnants of older rocks. Around ten million years ago, the Sierra Nevada was uplifted and then tilted to form its gentle western slopes and the more dramatic eastern slopes. This uplift increased the steepness of stream and river beds, which resulted in formation of deep narrow canyons. One million years ago, snow and ice accumulated which formed glaciers at the higher alpine meadows that moved down the river valleys. The ice thickness in Yosemite Valley possibly reached four thousand feet during the early glacial episode. The down slope movement of the ice masses cut and sculpted the U-shape valley that attracts many visitors to its scenic vistas today.

http://commons.wikimedia.org/wiki/File:General_geologic_map_of_Yosemite_area.png

Half Dome: Half Dome is one of the most popular attractions of Yosemite Valley. Standing at the eastern end of Yosemite Valley, this distinctive monument dominates most Valley views. Half Dome rises to an elevation of eight thousand eight hundred and forty two. At eighty-seven million years old, the granite that makes up the stone is the youngest plutonic rock in the valley. The remaining portions of the granite on Half Dome's face are believed to have sheared off during its cooling phase one hundred million years ago, deep under the seabed. Glaciers that have succeeded deposited some of the debris in moraines along the Valley floor.

Half Dome pictures taken by Dawnielle Burnell

El Capitan: Located on the north side of Yosemite Valley near its western end, stands the beautiful El Capitan. El Capitan is a three thousand foot vertical rock formation. This granite monolith is one of the world's favorite challenges for rock climbers. El Capitan is almost made entirely of El Capitan Granite, which is a pale, coarse-grained granite emplaced approximately one hundred million years ago. In addition to El Capitan, this type of granite forms most of the rock features of the western portions of Yosemite Valley. The uppermost portions of the cliff face are made of a separate intrusion of igneous rock, known as the Taft Granite. A third igneous rock, known as diorite, is seen as dark-veined intrusions through both kinds of granite. Along with most of the other rock formations of Yosemite Valley, El Capitan was carved by glacial action. Out of all the several glaciations that have occurred in the Sierra Nevada, the Sherwin Glaciations’ is considered to be responsible for the majority of the sculpting. The El Capitan Granite is free of joints. As a result, the glacial ice did not erode the rock face as much as the other, more jointed, rocks nearby. This rock formation is the most popular among tourists for rock climbing.





 

http://www.images-photography-pictures.net/california-yosemite-el-capitan.jpg

Yosemite Falls: Yosemite Falls is the highest waterfall (by measurement) in North America. Located in Yosemite National Park, it is a major attraction in the park, especially in late spring when the water flow is at its peak. The Yosemite Falls are often referred to as a “two-stage drop,” However, even though it is often referred to that name, the falls actually have three sections to them. The first section is the Upper Falls which is among the twenty highest waterfalls in the world. Trails from the valley floor and down from other park areas lead to the top and base of the Upper Falls. The second one known as the Middle Cascades, are a series of five smaller plunges. These plunges are taken together for a total drop of 205 meters. Because of the narrow, constricted shape of the gorge in which the drops occur and the lack of public access, they are rarely noted and the viewpoints in the valley miss them entirely. Several vantage points for these cascades can be found along the Yosemite Falls trail. The last one, known as Lower Falls, are the final ninety-seven meters drop that is adjacent t and accessible viewing area, provides the most-used viewing point for the falls. Like many areas of Yosemite, the plunge pool at the base of the Lower Falls is surrounded by dangerous jumbles of Talus. Many tourists can climb up the side to get closer view of the falls; however one must be extremely careful of the slippery rocks and the rushing water.

Yosemite Falls pictures taken by Dawnielle Burnell  

Yosemite National Park holds a lot of natural beauty and treasures that many hold as fond memories and continue on going for years to come. So long as Yosemite is taken care of and protected, many who have not had the chance to learn and experience this beautiful place will have the chance to do so if desired.

References

http://www.shannontech.com/ParkVision/Yosemite/Yosemite.html

http://www.ohranger.com/yosemite/history-yosemite

http://en.wikipedia.org/wiki/Yosemite_National_Park

http://thehive.modbee.com/?q=node/11711

http://en.wikipedia.org/wiki/El_Capitan

http://en.wikipedia.org/wiki/Yosemite_Falls