How are icebergs formed?

While icebergs tend to have a bad rap — most people instantly think of the Titanic disaster when they hear the word — they’re actually quite beautiful natural formations. An iceberg is a basically a large chunk of ice that has broken apart from a freshwater glacier. A glacier, which is a slab of ice and snow that can be hundreds of miles long, moves slowly under the force of its own weight until it eventually reaches the ocean. The edge of the glacier that extends out onto the water is known as the ice shelf. The ocean tides work with the weight of the glacier, causing chunks of the ice shelf to crack and eventually separate. The continual process of icebergs breaking off into the ocean is called “calving.”

Weather patterns, climate and calving cycles all affect how icebergs are formed, and glaciers in the Arctic form as many as 15,000 icebergs each year. While icebergs are generally formed in the far northern or southern regions of the Earth, they can float thousands of miles from where they originate — they’ve even been found near Bermuda!

Based on their shapes, icebergs are classified as tabular and non-tabular. Tabular icebergs are flat, floating sheets of ice. These are the most common type of iceberg, and they’re found in Antarctica. Non-tabular icebergs form in an assortment of shapes, including tall, irregular and cube-like. Sometimes they form canyons underwater with connected tips, or even arches, as the iceberg melts and reforms.

While most icebergs are blue, which in the color of the compressed glacial ice, or white, which is the color they turn after a few melt-and-freeze cycles, some icebergs can take on an impressive shade of green. This occurs when Antarctic icebergs that formed at the bottom of Antarctic ice shelves were in contact with seawater, which contains dissolved organic matter. When the ice shelves collapse and the icebergs begin to melt, some may flip over to reveal their green side — a combination of yellowish organic matter and the blue color of the ice


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