2 December, 2000
More Snow and Ice
Sometimes when I look around at the scenery it is easy to forget that, even though it may look like Kansas in the winter, there is over half a mile of snow and ice beneath my feet.
I've been here at Siple Dome for ten days. Except for some tiny falling crystals called diamond dust, it really hasn't snowed during that time. But when it does snow, it doesn't melt.
The 1000 meters of ice that forms Siple Dome contains an estimated 80,000 to 100,000 years of accumulated snow. Snow that survives a year is called firn. The firn layer extends down about 70 meters to a level where the air spaces or pores are no longer connected. Below the firn layer is ice. At even deeper levels, the pressure increases compressing the air bubbles in the ice causing them to shrink. At about 1000 meter, near the bottom of the ice sheet at Siple Dome, the air bubbles disappear into the ice lattice resulting in clear, blue ice.
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