Thermal Features, Yellowstone National Park
Old Faithful is the most famous of Yellowstone's thermal features but far from the most impressive. The park is full of geysers and boiling hot pools. The pools are crystal clear because most are so hot there is no bacteria or algae that can live in them. The runoff from the pools and geysers creates specular multi-colored algae beds as different colored algae live different temperatures and the run-off cools as it flows away from the source.