Ocean-Floor Convergence: A Contrary View of Global Tectonics

Some sea-floor spreading interpretations may be influenced by the ruling theory, and contrary evidence may be neglected. In the hope of promoting skeptical reexamination by specialists, I propose an alternative hypothesis, ocean-floor convergence, essentially the reverse of sea-floor spreading. Recent JOIDES data on increase of maximum sediment age with distance from the ridge seem to favor the spreading hypothesis, but many of the underlying basalts are sills and the picture may change with deeper drilling; how many additional layers of sediment lie beneath the uppermost basalt? Relatively high uranium, thorium, and potassium content of continental rocks favors the hypothesis of mantle upwelling beneath continents and of divergent flow away from continental margins and deep basins. The general heat-flow dilemma, approximate equality of continental and oceanic averages, can be explained by convective heat transfer from subcontinent to oceanic crust. Subcrustal creep in a direction away from continents is also consistent with the scattered segments of continental shelf which are being found in the deep sea. Magnetic anomaly correlations with the magnetic reversal scale seem questionable, particularly in the critical central section, and vulcanism near the ridge axis (Iceland, e.g.) apparently is destroying, not creating, the regular pattern of magnetic bands. The "convergence" hypothesis offers an explanation of some of the puzzles. It is too early to adopt a single preferred theory.