PerspectiveGeophysics

What Lies Beneath

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Science  02 Apr 2010:
Vol. 328, Issue 5974, pp. 54-55
DOI: 10.1126/science.1188090

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Summary

Since Archimedes shouted “Eureka!” more than 2200 years ago, Eurasia and North America have moved ∼55 m further away from each other as the sea floor has spread at the Mid-Atlantic Ridge. The slow but steady process of sea-floor spreading takes hot young lithosphere at the ridge axis and gradually moves it away as it cools, thickens, and sinks. Archimedes' principle of buoyancy rules much of these plate tectonic processes. On page 83 of this issue, Adam and Vidal (1) remind us that it is not just what sits atop that matters, but also what lies beneath. They show that mantle flow beneath the oceanic crust influences the depth of the Pacific Ocean. Taking advantage of new, easily accessible global geophysical data sets, the authors offer a new explanation for a long-standing mystery in the variation of sea-floor depth with crustal age.