Charting the abyss

Real-life adventure story reveals the daring efforts being made to map vast tracts of the world's unexplored seabed.

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In 1957, Marie Tharp published an unusual map. Instead of the land, the US scientist's map showed the floor of the Atlantic Ocean.

If you haven't seen it, or Tharp's later maps of the other oceans, you've probably seen versions of them - the seabed revealed in 3D, as if all the water has been drained away, revealing mountain chains running for thousands of kilometres and valleys deeper than anything above sea level.

Given how little of the seabed had been reliably surveyed, Tharp's maps relied heavily on creative licence, but they vividly delivered the message that the deep ocean floor is not a flat, featureless place.

They also helped to make the case for the idea of continental drift.

BY MARK FRYER

THE DEEPEST MAP by Laura Trethewey (HarperCollins, $75 hb)

Tharp is one of the key protagonists in Laura Trethewey's story of the effort to chart the unmapped areas of the seabed, a place which - as the cliché goes - we know less about than the surface of the moon.

Science has moved on since Tharp's day, though perhaps not as much as you might imagine.