Why are icebergs
such weird shapes?
We were told that icebergs, once they have "calved" off of the main ice sheet, will float with only about 20% of their surface above water. Air is a better insulator than water, so the underwater part melts faster than the top part, and at some point, the iceberg rolls over, exposing the underwater towers and crevices. This process can repeat several times, leading to some absolutely amazing shapes.
icebergs blue? There was some extremely lively debate among our onboard
scientists (both amateur and professional!), as to just why the icebergs
are such an amazing color of blue. After talking to several of them,
my understanding of the general consensus is the following: The Antarctic
ice sheet is extremely thick -- miles thick in places -- and the weight
of all of the ice causes the ice in the lower parts of the sheet to become
amazingly compressed. This extremely dense ice has all of the air
squeezed out of it, sort of like snowflakes that have been mashed into
the smallest possible space, and thereby lost all of the air bubbles in
their crystalline matrix. Ice without air in it, is naturally blue
in color. Less dense ice, however, has more air in it, and therefore
reflects light differently, hence the lack of blue. The blue can
also be enhanced when there's a part of the iceberg that's just below the
water... In some places, it looked exactly like a swimming pool.
Unheated, of course. ;)
Icebergs near Cuverville Island
Page last updated: March 12, 1999