As you embark or continue your journey to discover and explore beautiful and historic rocks, waterfalls, peaks, creeks and other wonders, please keep in mind that these places need to remain wild and protected so that they may be enjoyed by others for generations to come. Please be diligent in respecting these sites by doing the following:
Thank you, Yosemite Wilderness Management
- Please keep trash with you at all times, do not leave it behind in these pristine places.
- Bury human waste 6 inches deep, make certain you are at least 50 paces away from any water source and PLEASE bring your toilet paper and sanitary items back out with you.
- Keep food and all scented items on your person at all times.
- Support wildlife by allowing them to find their own food, do not feed them.
- Allow plants to grow and water to stay clean by staying on trails, bike paths and roads.
There is a small parking lot close by and a viewing platform built next to the road out to glacier point. There are no services here.
Across the valley from this viewing platform are Nevada Fall, Diamond Cascade, and Vernal Fall. These three sharp descents in the valley form the Giant’s Staircase. However they are only part of a series of glacial steps that start at the base of Mount Lyell and extend 21 miles to Yosemite Valley. In that distance there is a 7,600 foot elevation drop. This geomorphological feature resulted in the glacial erosion of sparsely fractured granite.
The Sierra Nevada Mountains are composed of the more than 100 individual plutons that are collectively called the Sierra Batholith. The batholith solidified deep underground between the Late Jurassic to Early Cretaceous (between 184 to 132 million years ago). As the rock above the pluton was eroded and the Sierra Nevada were uplifted, the pressure containing the pluton decreased. This allowed the pluton to expand. To accommodate that expansion, large cracks formed throughout the cooled granite. These cracks are called joints and are areas of weakness in the granite.
Millions of years later, during the Wisonsonian Glaciation that occurred between 70,000 and 10,000 years ago (divided into the Tahoe, Tenaya, and Tioga glaciations in the Sierra Nevada) glaciers eroded the various features found throughout Yosemite.
The Merced Glacier filled Little Yosemite Valley and flowed down into Yosemite Valley along the path of the Merced River. Before glaciation, the valley had an initial slope as shown by the dotted line (AA) in the figure below (USGS). As the glacier flowed over the joints in the granite, those areas were eroded at a faster rate than the areas with fewer joints .
The coordinates provide a good view of three of the steps that were created by the Merced River. The upper (Nevada Falls) and the lower (Vernal Falls) steps are the easiest to see. Diamond Cascade is in between and doesn’t create well defined step probably because the joints are not limited to a small area and the erosion was distributed over a wider area.
Above Vernal Falls is Little Yosemite Valley. The granite along that valley is unjointed and thus creates a long step. The upper steps (out of view) are much less defined than the three in front of you.
- The text "GC2M286 A View of the Giant's Staircase" on the first line
- The number of people in your group.
- What effect has continued water flow had upon the edges of the glacial steps?
- Based on the observation above, was the Merced Glacier or River more effective at eroding the granite? .
The following sources were used to generate this cache:
- Matthes, Francois. 1930 USGS. Geological Survey Professional Paper 160 Geologic History of the Yosemite Valley. http://www.nps.gov/history/history/online_books/geology/publications/pp/160/index.htm Last Updated: 28-Nov-2006
- Kiver, Eugene and David Harris. 1999. Geology of U.S. Parklands Fifth Edition, John Wiley & Sons, Inc.