Green Fly Geyser near Gerlach, Nevada. It was caused by a well drilling error which hit a geothermal spring. Mineral deposits have caused the ever-growing mound and the colors are caused by algae that grows in the hot water. It is on PRIVATE PROPERTY, the landowner has fenced it off due to bad behavior by idiots in the past. Go to Yellowstone instead to see the geysers and the colored algae.