Icebergs are made of freshwater ice
and not of frozen sea water. They form from the edge of glaciers
when the glacier reaches the sea and either break off in pieces to form
an iceberg, or in the case of an ice shelf, begin to float on the sea
and then break off from the rest of the glacier as a large slab.
Icebergs are made up of snow that has fallen over
many hundreds or even thousands of years. The stripes and different
coloured layers in icebergs represent different layers of snowfall and
the weather conditions under which the snow fell. If it is very cold
then a light open layer with much air included will be formed, this
gives a paler or white layer. The darker, bluer layers come from snow
fall in relatively warm, maybe even wet conditions when little or no
air is trapped in the layer.
In addition to this, air is squeezed out of the lower
layers of a glacier as more and more snow falls and so the weight of
snow builds up.
Paul Ward - Pentax equipment, 50mm
lens, 35mm film, K64.
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