When glaciers reach water, whether it's a lake or the ocean, they break off in pieces. The smallest pieces are called brash ice (less than 2 meters across), and larger pieces are called growlers (less than 10 m long) or bergy bits (up to 20 m across). This is definitely an iceberg. Glacial ice has a distinctive blue tinge and may contain streaks or coatings of sediment. Ordinary sea ice is white or clear, and never very thick.
Icebergs have a bit less than nine-tenths of their volume under water. Icebergs are not pure ice because they contain air bubbles, often under pressure, and also sediments. Some icebergs are so "dirty" that they carry significant amounts of sediment far out to sea. The great late-Pleistocene outpourings of icebergs known as Heinrich events were discovered because of the abundant layers of ice-rafted sediment they left across much of the North Atlantic seafloor.
Sea ice, which forms on open water, has its own set of names based on various size ranges of ice floes.
