They say the Badlands erode at the rate of about 1/2″ a year. That got me to wondering how high they were 100 years ago and how high they would be 100 years from now. But then I realized that while their elevation relative to sea level would change, their local height (measured from the bottom of one of the formations to its top) might not. In fact it might even increase depending on whether the gullies and washes between the formations erode faster or slower than the formations themselves. That’s something I should have asked about when I was in the visitor’s center I guess.