The colorful hills dominating the view in front of you give us clues to what life was like in Big Bend around 65-70 million years ago. An inland river-floodplain environment existed at that time, nurturing animals including fish, reptiles and dinosaurs. This fluvial system deposited the sands and muds that created these colorful ancient soils. Fossils and bones of ancient animals have been found throughout the park where these colorful soils exist. This was also a time of great change for life on Earth. Around 65 million years ago, dinosaurs went extinct, making way for the rise of mammals.