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Granite Rushmore

A cache by csr212 Send Message to Owner Message this owner
Hidden : 09/04/2011
1.5 out of 5
1.5 out of 5

Size: Size:   other (other)

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Geocache Description:

"Mount Rushmore National Memorial sculpture is carved into the granite face of Mount Rushmore near Keystone, South Dakota, in the US. Sculpted by Gutzon Borglum and later by his son Lincoln Borglum. Mount Rushmore features 60-foot sculptures of the heads of former United States presidents; George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln.

The Park does have an $11.00 Parking fee to visit.
Mount Rushmore is largely composed of granite. The memorial is carved on the northwest margin of the Harney Peak granite batholith in the Black Hills of South Dakota, so the geologic formations of the heart of the Black Hills region are also evident at Mount Rushmore.
The batholith magma intruded into the pre-existing mica schist rocks during the Precambrian period about 1.6 billion years ago.
Very coarse grained pegmatite is associated with the granite of Harney Peak. The light-colored streaks in the presidents' foreheads are due to these dikes.
The Black Hills granites were exposed to erosion during the late Precambrian, but were buried by sandstones and other sediments during the Cambrian Period.
The area remained buried throughout the Paleozoic Era, but was exposed again to erosion during the tectonic uplift about 70 million years ago. The Black Hills area was uplifted as an elongated geologic dome.
The subsequent natural erosion of this mountain range allowed the carvings by stripping the granite of the overlying sediments and the softer adjacent schists. The contact between the granite and darker schist is viewable just below the sculpture of Washington.
Borglum selected Mount Rushmore as the site for several reasons. The rock of the mountain is composed of smooth, fine-grained granite. The durable granite erodes only 1 inch every 10,000 years, indicating that it was sturdy enough to support sculpting. In addition, it was the tallest mountain in the region, looming to a height of 5,725 feet above sea level. Because the mountain faces the southeast, the workers also had the advantage of sunlight for most of the day.

For directions and Park hours please visit Photobucket

To log this Earthcache: e-mail the answers to the questions below.
1. What was the original design of Mount Rushmore, Why was it not followed?
2. Why is the Granite at this location ideal to carve.
3. What other rock formation was a potential carving site? Why was that mountain not used?
Optional: Post a pic of anywhere in the park with your GPS, or a pic of yourself from in the park.

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