Calcite Springs, a thermal feature in the northeast corner of Yellowstone National Park, is one of the park's lesser-known thermal features.

It’s a beautiful exposure of white calcite crystals and steam vents on a sheer cliff cascading into the pristine waters of the Yellowstone River below.

However, sharp-eyed onlookers will notice streams of a gloopy, black, tar-like substance streaking the side of the white cliff, often rolling into giant, ugly balls. It’s seemingly out of place and unsettling, blemishing the otherwise serene surface.

Some will tell you it’s rivers of brimstone from the depths of hell, while others say it’s a vein of black gold, revealing untold riches right under the surface.

Actually, it’s both — smoldering, sticky, super smelly and completely natural.

The Stink

See Full Page