Blue ice
Q: Why is some ice blue? Sherie, Albuquerque, New Mexico
![[NOAA] An iceberg and blue ice, Gerlache Strait, Antarctica](iceberg-antarctica1.jpg) An
iceberg and blue ice, Gerlache Strait, Antarctica. Photo courtesy of NOAA.
A: Ice is blue for much the same reason that water is blue--it absorbs a bit
more of the red-frequency part of light that shines on it than it does the blue.
Poke a hole in snow or ice and look down it. You'll see blue-green light
because the emerging light has bounced around through many snow-particle
passages. At each snow collision, the snow absorbs more red than blue.
Eventually, the reflected light is noticeably blue. The white light fades to
blue as it bops its way out. The deeper the ice hole, the bluer the returning
light.
Sometimes icebergs look green instead of blue. Icebergs contain more stuff than ice---suspended sediments, algae, and air bubbles. These
particles contribute to the green color.
Further Reading
Color and Light in Nature by David K. Lynch and William Livingston
(Answered Dec. 13, 2002; updated
Sep. 28, 2007)
Click for printer version.
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