When scientists talk about the cryosphere, they mean the places on Earth where water is in its solid form, frozen into ice or snow. Read more ...
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unlike snow dunes that are piles of drifted snow, antarctic megadunes are long, undulating waves in the surface of the ice sheet that are 2 to 4 meters (6.5 to 13 feet) high and 2 to 5 kilometers (1 to 3 miles) apart; they are slightly rounded at their crests and are so subtle that a person on the ground cannot see the pattern.
This NASA satellite image shows a five-mile scale in a megadune area