Geophysics

Reconstructing Plate Tectonics

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Science  20 Sep 2013:
Vol. 341, Issue 6152, pp. 1321
DOI: 10.1126/science.341.6152.1321-b

The modern-day distribution of Earth's tectonic plates is just a snapshot of an ever-changing process. Reconstructions of previous plate arrangements have resulted in the identification of the ancient supercontinents Pangea and Rodinia, but does this cycle follow any sort of predictable law o r pattern? Morra et al. statistically analyzed the organization of large and small plates across Earth's surface over the past 200 million years, based on models of plate reconstructions. Small plates do not show much statistical variation in their distribution over time, because they are largely unstable and form from unrelated events. Large plates, however, tend to organize either into heterogeneous or homogenous states based on plate size distributions over ∼100-million-year time scales. The rapid rate at which heterogeneous distribution states are stabilized suggests that these may be excited states, whereas homogeneous distribution states tend more toward equilibrium. In this case, the underlying driving force for the transition from one state to another depends on cycling between top-down and bottom-up mantle convection as a control on plate motion.

Earth Planet. Sci. Lett. 373, 93 (2013).

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