With just a little help from a geologist, these rocks make it possible to see what cannot be seen and travel through time for millions of years. They reveal long-gone river valleys, open oceans, and enormous volcanoes, and show a time when plants, animals, and climate were different from what is known today. The Morrison Formation preserves a world of herds of dinosaurs grazing alongside streams while turtles and crocodiles slipped into the waters and termites moved through underground nests. The Dakota Sandstone formed from warm river valley habitats and contains fossils of lush flowering plants and trees. The Mancos Shale was deposited in the ancient waters of a broad inland sea whose ocean waters covered Colorado. The West Elk Breccia preserves a mudflow from the West Elk Volcano, frozen in time. The Blue Mesa Tuff is cemented ash from towering volcanoes once found near the present-day San Juan Mountains.