Plate Tectonics by Iain Stewart

Author:Iain Stewart
Language: eng
Format: epub
ISBN: 9781405930734
Publisher: Penguin Books Ltd
Published: 2018-02-12T16:00:00+00:00

The first touching of a new world

The ocean floor’s geomagnetic barcode could only track sea-floor spreading if the ages of the basalt stripes were known. Age-dating the basalt, however, meant drilling in thousands of metres of water and through the thick, muddy seabed. A single deep hole through the entire ocean crust and into the mantle below had been proposed, but in 1961 the ambitious and costly Project Mohole was abandoned after boring just 13 metres into the basalt basement. Reporting from the drilling barge, the writer John Steinbeck celebrated a heroic failure – equivalent to ‘Columbus’s first feeble voyage of discovery’ – predicting that ‘on this first touching of a new world the way to discovery lies open’.

Steinbeck was right. The ill-fated Mohole project energized the earth science community. Over the next few years, the USA began to put together the Deep-Sea Drilling Project, to be operated out of Scripps Institute of Oceanography, with a strategy of lots of shallow boreholes rather than grand scientific gestures. A specialist ship was designed and built, a modern version of the venerable Challenger a century before.

In 1968, the Glomar Challenger set off into South Atlantic waters for its first mission: to put sea-floor spreading to the test. Compelling zebra stripes of magnetic reversals had been revealed across many of the world’s ocean ridges but many of the scientists on board remained deeply sceptical; they returned two months later devout converts. The ages from nine short holes drilled across the Mid-Atlantic Ridge perfectly fitted a speculative timescale proposed by the Lamont oceanographer Jim Heirtzler. The oceans now had a barcode reader that could reconstruct their magnetic histories.

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