In the Antarctic, the ice breaks off in great sheets, hundreds of miles on a side. The submerged core is made of rock-hard, freshwater ice. The average age of that ice is thought to be about 5,000 years. But some may date back to the last ice age. In their glory, icebergs can tower hundreds of feet above the water.
Icebergs come in all shapes and sizes.
Riding the Labrador current, some of the icebergs make it to the North Atlantic. Along the way, many are lost to groundings in shallow water or simply disintegrate in the sun. Some years, only a few hundred icebergs are spotted in the North Atlantic. In the summer, the iceberg armadas begin to crumble. It forms from frozen seawater, as its name suggests, not compacted snow.