Here are some more photos I took at Badlands National Park near Wall, SD in early September.
The Badlands consist mainly of sedimentary rocks deposited from 26 to 75 million years ago. Erosion from rivers and streams began 500,000 years ago and is occurring at the rate of one inch per year. So this area is constantly changing from one year to the next, and it is estimated that it will be completely eroded in another 500,000 years.
Sedimentary rocks are friable. When you walk on them, it feels like walking on compacted sand that crumbles under your feet. People do hike trails that go up ridge lines so that they can explore and view the area from some height. Many fossils have been found in the various rock layers, and more fossils continue to be discovered as erosion uncovers them.