Angular red, purple, gray, and green rocks here show a geologic transition between the soft rock of the prairie and the erosion-resistant igneous rock of the Adel Mountains. These volcanic rock fragments were blasted skyward by violent volcanic activity some 68 to 75 million years ago, then settled and were cemented together with volcanic ash. Over time, the less erosion-resistant rock washed away, revealing the formation seen today. This area is also a good example of a habitat edge, where the prairies meet the mountains, and its rich diversity provides important places for wildlife to get water, nest, and seek prey. A botanical study found over 100 species of prairie and mountain plants here that are found nowhere else but along mountain edges.