Are Icebergs Made of Freshwater or Saltwater?

Michael Leggero/Getty images

Icebergs form from a variety of processes, yet even though they may be found floating in salty seawater, they are primarily made of freshwater.

Icebergs form as a result of two main processes, producing a freshwater iceberg:

  1. Ice that forms from freezing seawater typically freezes slowly enough that it forms crystalline water (ice), which does not have room for salt inclusions. These ice floes are not truly icebergs, but they can be extremely large chunks of ice. Ice floes typically result when the polar ice breaks up in the springtime.
  2. Icebergs are "calved," or form when a piece of a glacier or other land-based ice sheet breaks off. The ​glacier is made from compacted snow, which is freshwater.