Template:POTD/2011-09-15

Picture of the day

Mammoth Hot Springs is a large complex of hot springs on a hill of travertine in the United States' Yellowstone National Park. It was created over thousands of years as hot water from the spring cooled and deposited calcium carbonate. Algae living in the warm pools have tinted the travertine shades of brown, orange, red, and green.Photo: Mila Zinkova