A steam devil is a small, weak whirlwind over water (or sometimes wet land) that has drawn fog into the vortex, thus rendering it visible.
Smaller steam devils and steam whirls can form over geyser basins even in warm weather because of the very high water temperatures. Although observations of steam devils are generally quite rare, hot springs in Yellowstone Park produce them on a daily basis.
en.wikipedia.org/wiki/Steam_devil
Built up over millennia by heat-loving microorganisms and minerals precipitating out of the hydrothermal waters, sinter terraces surround the Grand Prismatic Spring - the largest hot spring in the USA - at Yellowstone National Park, Wyoming. The terraces are also home to larger organisms - note the bison hoof prints in the foreground.
Putting on a typical show.
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Continually on the boil, one of the geothermal springs at the Mud Volcano area, Yellowstone National Park.
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