One can't go to Yellowstone National Park and not visit the hot springs there is how ever a little known fact that I think not many people know. There are two types of hot springs in the park the ones above are calcium carbonate hot springs in which the bacteria along with the cooling waters precipitate out calcium carbonate. It's pretty cool to get a look as the springs grow new "matts" are formed as the new bacteria grows ontop of previously percipitated calcium carbonate. The other type of hot spring are silisious hot springs which precipitate silicon but I'll stop boaring you all with the long lecture and let you enjoy the scenery