Check this out. At each of these overlooks there's a description of what the history is of these particular parts of the desert. In the distance, you can see that different layers of the rock have different colors. You can see a point where the rock turns from red to white. The sign in front of me here explains that this color difference means that there was about 1000 years of rock layer that was washed away, before the newer, lighter colored rock was deposited in recent centuries. So basically theres a thousand missing years where it goes from red to white.