Yellowstone National Park
Yellowstone National Park has one of the world's largest petrified forests, trees which were long ago buried by ash and soil and transformed from wood to mineral materials. This ash and other volcanic debris are believed to have come from the park area itself as the central part of Yellowstone is the massive caldera of a supervolcano. The park contains 290 waterfalls of at least , the highest being the Lower Falls of the Yellowstone River at .
Emerald Pool
Emerald Pool, a hot spring named for its emerald green color, is one of the main attractions at Black Sand Basin in Yellowstone National Park. Its temperature is 154.6 °F and its dimensions are 27x38 feet with a depth of 25 feet. The color is due to growth of yellow bacteria and algae. Cooling, the result of objects thrown into the pool and natural debris, has affected the growth of the bacteria and algae, making the pool appear orange and brown around the edges.