A team of preservation experts from the National Parks Service is currently laying new tracking equipment across Mount Rushmore. The Rapid City Journal reports that the purpose of the new fiber optic equipment is to track any new shifts or cracks that appear on the monument so that any decay or rock abnormalities can be fixed quickly and accurately. The old copper lines that were previously on the mountain only updated so often while the new lines will deliver near instantaneous data.
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For more information on Rushmore itself, check out the monument's homepage.