Amazingly vibrant color, more than any other single thing, is what puts Yellowstone in a league all by itself. For some unknown reason, though, the park’s collection of frequently erupting geysers gets most of the attention. Old Faithful, it seems, is as much a national landmark as the overexposed giant heads of Mount Rushmore. But seeing a column of water burst from the ground like an ordinary city fountain is every bit as exciting as it sounds. Having to wait 90 minutes or more to actually see one makes it decidedly less so.
Thermophiles, meanwhile, are as underappreciated as the water spouts are overhyped. These incredible heat-loving microbes literally put the yellow into Yellowstone.
Thriving at various temperatures, different thermophiles take up residence in different hot water springs and pools. Cooler water is hospitable to green and brown colored organisms.
Orange and yellow indicates hotter temperatures.
Fewer creatures survive in springs with temperatures near the boiling point. In these locations, the clear water shines emerald blue.