According to Wikipedia, the Colorado Plateau rose up 20 million years ago.
-Based on 7 in of erosion / 1000 years, in 20 million years, 11,666 ft would erode. The Colorado plateau is currently between 5000-7000 ft elevation.
So was the plateau 17,000 ft tall??
Map Picture Source from: https://www.livescience.com/39218-colorado-plateau-geology-photos.html