Upheaval from the Abyss: Ocean floor mapping and the earth science revolution
by David Lawrence, Rutgers University Press, $28, ISBN 0813530288
ON 14 February 1873, 1500 metres below where I have just finished reading
this book, one of the most famous research vessels of all
time鈥擟hallenger鈥攕ailed from Tenerife on its epoch-making journey
around the world.
Tenerife is a volcano, standing 3 kilometres tall, but that鈥檚 only half the
story. Its roots reach down 3 kilometres beneath the sea to the floor of the
abyss, atop a pile of basalt that erupted more than 11.6 million years ago. To
the west, the Atlantic stretches to the horizon. Yet the floor of this vast
ocean unzipped itself from south to north over a period of hundreds of millions
of years, creating the matching shores of Africa and South America. In its
middle the spreading ocean floor bisects and mirrors their matching profiles.
The invisible magnetic 鈥渟tripes鈥� that mark the pattern of the reversals of
Earth鈥檚 magnetic field are frozen in this floor as if it were a recording tape.
But back in 1873, Challenger鈥檚 scientists didn鈥檛 even know how deep the oceans
were, let alone how they originated, or what made up their floors.
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The geologists and geophysicists who answered those questions created our
modern, plate-tectonic world view. This enjoyable book is their story, and
although the learning curve began with Challenger, Lawrence begins the tale with
Alfred Wegener鈥檚 death in 1930 on the Greenland ice cap. Wegener truly set the
continents in motion, and continental drift鈥攇odfather to plate
tectonics鈥攊s the book鈥檚 true scientific starting point.
Like that other breaker of worlds, Charles Darwin, Wegener set out to write a
tome so all-embracing that nobody, surely, could deny the evidence. But unlike
Darwin, Wegener lacked a mechanism for his theory. As a result, specialists
would always find some nit to pick from the evidence. So for more than 30 years,
few took in drift theory鈥檚 amazing synthetic power. Geophysical study of the
ocean floor eventually broke the deadlock.
It cannot be coincidental that the two great 20th-century revolutions in
geoscience鈥攄eep time and plate tectonics鈥攚ere both confirmed by
geophysicists decades after physics itself had pronounced them impossible. When
geologists wanted the Earth to be hundreds of millions of years old, Lord Kelvin
said no. Alas, radioactivity had not yet been dreamed of in the good Lord鈥檚
philosophy. Eventually geophysicist Arthur Holmes proved that what
stratigraphers had dreamed in their beds, and palaeontologists felt in their
bones, had been right all along.
At one point in his book, Lawrence wonders why, with all the evidence for
continental drift, geologists did not just believe their senses and worry about
mechanisms later. A few did. One of the Geological Society鈥檚 senior fellows told
me recently how, as a cocky young postdoc and a lone drifter in a department
full of sceptical physicists, he told them: 鈥淎ll I know is, it happened. The
mechanism is your bloody problem!鈥�
But geologists with that kind of nerve were few. It took the work of
Lawrence鈥檚 heroes鈥攊nstitutions and people, including another largely
unsung woman scientist, Marie Tharp鈥攖o show how useful the Queen of
Sciences (physics) can be, once she gets off that throne of hers and does
something useful.
El Teide, Tenerife鈥檚 majestic volcano, towers above me from neither a
subduction zone nor a spreading centre. According to some experts, it may not
even be a classic mantle-plume hot spot like Hawaii. But the bigger picture is
not threatened by this anomaly. Local peculiarities often prevail in geology,
which distinguishes it from physics and鈥攆or some鈥攍ends it a peculiar
charm.
Robert Graves scornfully wrote (allegedly of Jacob Bronowski): 鈥淗e is quick,
thinking in clear images.鈥� All physics鈥� hasty early interventions beyond the
realm of the ideal had that problem. Down in the abyss, things are
muddier鈥攁s Lawrence鈥檚 Upheaval from the Abyss engagingly
reveals.
Rest assured, though, the Earth continues to pack enough surprises for
everyone, and will always be more complex than our models, whether they are
produced by geologists, physicists鈥攐r anyone else, for that matter.