Iceberg

ocean · ice · geology · maritime hazard

Massive floating ice. Icebergs are pieces of ice bigger than 15 meters long that break away from glaciers and ice shelves, then drift freely in the ocean. They start out on land but eventually float away into open water.

Mostly underwater. About 90 percent of an iceberg sits below the water's surface, which is why the phrase 'tip of the iceberg' means you're only seeing a small part of a much bigger problem. What you see floating above is just a small hint of the whole thing.

Danger at sea. Icebergs are serious hazards for ships because they can damage or sink boats that hit them. Sailors have to watch carefully for icebergs, especially in areas like the North Atlantic where many of them float.

Fresh water, not salt. Unlike the salty ocean water around them, icebergs are made of fresh water that came from glaciers on land. This fresh water ice is different from the salty sea ice that forms directly from ocean water.

Smaller cousins exist. Even smaller chunks of floating glacier ice have special names: growlers and bergy bits. These tiny pieces are still dangerous because they're hard to spot from ships.