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Back to category: Science Limited version - please login or register to view the entire paper. The Evolution of Plate Tectonics A central problem in understanding the Earth system is the relationship between mantle convection and near-surface structure, geophysics and geochemistry. Unexplained anomalies of the plate tectonics (PT) model are the postulated mechanism of generating the axial rift valley by upward movement of marginal fault blocks, contrary to observations in the Icelandic rift, and the mechanism by which a postulated broad upwelling plume can yield the required narrow zone of axial volcanism. These discrepancies are the basis for a critical reappraisal of other evidence. It is shown that the generation of oceanic magnetic stripes, which led to the ingenious spreading hypothesis, is a result of narrowing of a formerly expanded ocean ridge volcanic system, and resultant sequential cooling of crust and upper mantle, and does not require ocean floor spreading. An alternative ridge model postulates sub-continent upwelling, sub-ridge convergent flow and generation of mid-ocean ridge basalt ... Posted by: Carmen hershman Limited version - please login or register to view the entire paper. |
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