What makes icebergs flip over?

Even mountain-sized icebergs weighing hundreds of millions of tonnes have been known to flip over, creating tsunamis capable of swamping nearby vessels.

14th April 2014

Asked by: Simon Woods, Braunton

Icebergs are notorious for keeping around 90 per cent of their bulk hidden beneath the surface of the sea. While this makes them far more dangerous to shipping than they appear, it does mean they’re extremely stable, and unlikely to wobble about. Yet even mountain-sized icebergs weighing hundreds of millions of tonnes have been known to flip over, creating tsunamis capable of swamping nearby vessels.

The risk is highest just after the birth of an iceberg from the edge of a glacier. As it breaks away, the iceberg tumbles off into the ocean, its irregular shape leading to the berg swaying or even flipping right over as gravity seeks to bring most of its weight beneath the sea surface. According to research published in 2011 by Prof Justin Burton and colleagues of the University of Chicago, the resulting motion can release as much energy as an atomic bomb.

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