The most vibrant colors in Badlands National Park can be admired at the Yellow Mounds Overlook. Many of the rock formations resemble giant scoops of rainbow sherbet. These are the remnants of the Pierre Shale. The deposition formation dates back 75 million years. As the Western Interior Seaway drained away, the warm water left behind fossilized soil called a paleosol. The mustard color of the Yellow Mounds is attributed to a mineral named goethite. The iron oxyhydroxide is basically rust.
