Mount Rushmore, South Dakota

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Someone really needs to tell the people who digitize maps for the USGS that contour lines don't end. There are legibility reasons for omitting contours on paper maps but no excuse for doing so on digital maps.

Before The Desecration

After 9-11, a number of articles warned that Mount Rushmore might be a terrorist target because of its patriotic significance. Osama needn't worry. The National Park Service beat him to it.

Here's the monument in December, 1981. A modest paved trail led through the woods to the base of the carvings. Flagpoles for state flags lined the way (The tablet faintly reads "Wisconsin). A rustic timber visitor center and viewing deck served visitors.

From Monument to Mall

The modest walk through the woods has now been replaced with a sterile expanse of concrete And the rustic visitor center that blended well with the setting has been replaced by a shopping mall.

In the summer this place is indeed crowded, but a glance at the most detailed map above will show there's a rather large ridge extending south from the parking area that could have been used to expand parking. Or - here's a radical idea - widen the highway to permit shoulder parking and safe photo stops. Instead the parking area was replaced by a multi-level garage to heighten the shopping mall effect. Needless to say, your Golden Eagle won't cover the parking fee.

Just west of the parking area are some wonderful outcrops of pegmatite and metamorphic rocks. When I was here in July 2004 the shoulder was blocked by barricades, possibly for safety but more likely lest someone, horror of horrors, park for free and walk around the corner to get in.

The Approach From Keystone

   

The Faces

Tablet commemorating the Rushmore carvers
View down the avenue of flags
View from a now-closed service road below the parking area.
From left to right, in case you need a refresher, the faces are Washington, Jefferson, Theodore Roosevelt, and Lincoln. No, there are no plans to add other faces and probably not enough sound granite to permit it.

Roosevelt was controversial because he was a friend of Borglum's and had only been dead a short time when the memorial began, but few argue with the choice now.

The neat thing about the intrusion at Mount Rushmore is you can see the bottom of it. The contact between granite and schist is plainly visible midway down Washington's chest.

A large horizontal granite dike is visible just above the talus pile and a big vertical dike to Washington's lower left. These are probably feeders of the granite.

This guy made a very good Abe Lincoln. Not only did he look the part but he had a folksy style and sharp wit that probably reflect Lincoln better than the dignified portrayals in most films.

Washington's Profile

This was an accident. Jefferson was supposed to be here but not visible from this location. The granite turned out to be unsound and the face was blasted off, making it possible to see Washington in profile.
Migmatites at the profile view parking lot. Photo taken in 2004. Ductile deformation is common around pegmatite bodies in the Black Hills and probably indicates the metamorphic rocks were pretty hot. In some cases the ductile deformation gives the impression of being due to loading by granitic intrusions above.
Close up of the pegmatite pod above, but taken in 1999. Note the growth of the tree between this photo and the one above.

The Base of the Carvings

Local Geology

Left: Metamorphic rock outcrop on Mount Rushmore.

Below: Knobs of granitic rock standing out because of greater resistance to erosion.

 
Schist overlain by granitic intrusion.
View southeast. The ridges are hogbacks of Paleozoic and Mesozoic rocks.
Contact between schist (below) and granite (above)
Schist xenolith in granite
Left and below: Pegmatite lenses in granite.

Fossil Tracks?

Dinosaur tracks in Precambrian schist? I don't think so. I suspect these are rather like kink bands. These are just at the entrance to the trail to the base of the carvings.
 
On the other hand, there's little doubt about how genuine these tracks are.

Iron Mountain Parkway

Left: All the tunnels on the parkway look directly at Mount Rushmore

Below: Views from Iron Mountain Lookout

Left: Distant view from Iron Mountain Parkway

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Created 29 July 2004, Last Update 01 July 2012

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