How do icebergs form and how large can they get?

The answer

Icebergs form when chunks of ice calve, or break off, from glaciers, ice shelves, or ice sheets where they meet the ocean. The largest iceberg ever recorded, B-15, calved from Antarctica's Ross Ice Shelf in 2000 and measured approximately 295 kilometers long and 37 kilometers wide, covering an area of about 11,000 square kilometers. Only about 10% of an iceberg's mass is visible above water, giving rise to the expression 'tip of the iceberg.' Antarctic icebergs tend to be flat-topped and tabular, while Arctic icebergs from Greenland are more irregularly shaped. Some icebergs carry sediment and rock from land, and as they melt, they fertilize the surrounding ocean with iron, triggering phytoplankton blooms.