Entering the park from Gardiner, Montana, (the north entrance), the first thing you get to, after the little village with grocery stores, souvenir shops, and a gas station, is the Mammoth Hot Springs. The springs are caused by a scalding hot subterranean river that seeps up through cracks in the surface, bringing up dissolved limestone which recrystalizes at the surface and forms a gray mineral called travertine, which forms the terraces. The water temperature is about 130 to 168 degrees F. The travertine forms at the rate of two tons per day. The smell, which smells like rotten eggs or a paper mill, is caused by sulfates combining with hydrogen in the water to form hydrogen sulfide.
The colors are provided by micro-organisms that survive in this hot environment.
I thought I would share a photo of myself and my two understudies on this adventure.