Michael A. Stecker
mastecker@gmail.com
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Icebergs
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Their Physical Characteristics
Icebergs are beautiful fragmented shapes of
freshwater ice usually found floating in the ocean. They originate from a
mass of ice that has broken off a glacier (called a calcen) and has fallen
into a nearby body of water. They are therefore of freshwater origin from
precipitation (snow) that formed the glacier. In contrast, sea ice is
frozen sea water of salty content. Icebergs come in different colors --
white, cyan, light blue, dark blue and green. White is the standard color
and is a result of many tiny air bubbles in the superficial snow and ice
reflecting and scattering all colors of light -- i.e appears white. In
contrast, blue icebergs are made up of ice deep within the glacier which
has compressed most of the air out of the ice and has very few air
bubbles, so it shows its natural blue color. The ice now tends to absorb
light in the red region of the spectrum and the light that you see from
this kind of an iceberg will appear blue. Although icebergs are from newly
broken off glaciers (that may be thousand years old), they're often mixed
with flecks of black and brown from ground up rock. Their unusual shapes
are caused by weathering effects from wind, waves and melting. Some of the
icebergs that have broken off of the Antarctic ice shelves have been
monsters - one was the size of the state of Conneticut! In the Arctic,
icebergs are smaller. Car or house-sized icebergs are sometimes called
"growlers." The smallest icebergs are known as "bergy bits".
For a more technical discussion of the blue color of
water and ice, see:
http://webexhibits.org/causesofcolor/5B.html
and
http://webexhibits.org/causesofcolor/5C.html)
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