Green water thunders over the crest of Yellowstone Falls in Yellowstone National Park, Wyoming.

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Grotto Geyser in the Upper Geyser Basin of Yellowstone erupts in a plume of steam.

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Orange flow

Hot water, colored by bacteria, flows from a hydrothermal feature of West Thumb Geyser Basin into Lake Yellowstone.

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Thermophiles - heat-loving organisms - produce interesting colors in Yellowstone's hot springs.

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A golden-mantled ground squirrel nibbles on green leaves in Yellowstone National Park.

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This is a close-up of the fascinating Mammoth Hot Springs in Yellowstone NP. Mammoth is a large hill of travertine that has been created over thousands of years as hot water from the spring cools to around 170°F and deposits layers of calcium carbonate. The brown, orange, and red colors come from algae living in the warm pools which tint the white travertine.

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