29
May 2003
Ocean ridge formation: Twenty million years under the sea
 |
(On
the cover, a perspective view of the Verma transform valley.) |
In 1989 observers aboard the French submersible Nautile, diving near the Verma transform fault on the Mid-Atlantic Ridge, explored an uplifted sliver of undeformed ocean lithosphere exposed on the sea floor. It turned out to be part of a 300-km-long lithospheric section, equivalent to 20 million years of lithosphere creation. This remarkable outcrop provides a unique opportunity to study the processes of lithosphere formation at a ridge segment over an extended timescale. Gravity and geochemical data reveal oscillations of mantle melting and crustal thickness with periodicity of 3–4 million years. One surprise is that the Mid-Atlantic Ridge has become steadily hotter during the past 20 million years.
Mantle
thermal pulses below the Mid-Atlantic Ridge and temporal variations in the formation
of oceanic lithosphere
ENRICO BONATTI , MARCO LIGI,
DANIELE BRUNELLI, ANNA CIPRIANI, PAOLA FABRETTI, VALENTINA FERRANTE, LUCA GASPERINI
& LUISA OTTOLINI
Nature 423, 499–505 (2003); doi:10.1038/nature01594
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Earth science: A slice of history
PAUL
D. ASIMOW
Investigations of an exposed slice of oceanic crust and mantle have
provided a dramatic picture of temporal variation in the activity of the Mid-Atlantic
Ridge — including its pulse rate of 3-4 million years.
Nature
423, 491–493 (2003); doi:10.1038/423491a
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