Icebergs: Floating Snow Cones

Icebergs—giant blocks of ice that float in the sea—come in many shapes, sizes, and colors. Some are deep blue or green. Some look like floating sculptures. Old icebergs that have been worn down by the weather sometimes look like pillars of ice.

How is an iceberg formed? Icebergs begin and end in the ocean. First, moisture from the ocean rises into the air and moves up into Earth's atmosphere. Over Antarctica, where air is cold, the water falls as snow. As layers of snow develop, their heavy weight presses down and turns the snow to ice in the frigid polar climate—lots of ice. In fact, 90 percent of all the world's ice is on the continent of Antarctica. Huge areas of ice called ice sheets and glaciers move slowly across the continent toward the sea. (The fastest-moving Antarctic glacier moves about 1.25 miles in a year.) When glaciers finally reach the coast, huge pieces split off into the ocean. These are icebergs.

Scientists call the splitting off of icebergs “calving.” Icebergs are a lot larger than a calf, though. One of the largest Antarctic icebergs formed recently is 185 miles long and 25 miles wide.

Usually, only about one-fifth of an iceberg appears above the surface of the water. The other four-fifths of the “berg” is hidden underwater, out of sight. Sometimes, an iceberg has what is called a “foot,” an extension completely underwater. These are especially dangerous for ships. It was an iceberg “foot” that sank the Titanic in 1912, killing 1,503 people.

Every year, thousands of new icebergs are formed in the ocean around Antarctica. If you're lucky, you'll get to see one someday.


A large mass of ice that moves very slowly down a mountain or through a valley.

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  1. What form of water is an iceberg?
  2. How is the formation of an iceberg part of the water cycle? Draw a diagram that shows the steps of the water cycle as an iceberg is formed in Antarctica. Show each of the steps involved. Label each part of your diagram with words that you learned in Lesson 1.