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Claude Daley, Ice Engineer at Memorial University in Newfoundland, has studied how icebergs change personality at sea.

Observing a controlled experiment using a block of ice floating in water, Daly explains how the water melts the iceberg at the water line while the sun melts the top of the ice. With these different melting processes, ice hangs over the water line while a mass of ice remains hidden beneath the water.

With the tremendous weight of the iceberg pulling it down and the buoyant forces of the water pushing up, potential energy equivalent to a large explosive device is created. Like a coiled spring, an iceberg can unleash this energy at any moment.

As icebergs age they become less and less stable, melting and rolling continually at increasing speeds. They also constantly change shape. By this stage, the Titanic iceberg was less than a tenth of its original size, rolling over every three or four days and melting fast. At most it had two weeks of life left as it was drawn through 'iceberg alley', right into the transatlantic shipping lanes.