Runaway subduction. John Baumgardner created the runaway subduction model, which proposes that the pre-Flood lithosphere (ocean floor), being denser than the underlying mantle, began sinking. The heat released in the process decreased the viscosity of the mantle, so the process accelerated catastrophically. All the original lithosphere became subducted; the rising magma which replaced it raised the ocean floor, causing sea levels to rise and boiling off enough of the ocean to cause 150 days of rain. When it cooled, the ocean floor lowered again, and the Flood waters receded. Sedimentary mountains such as the Sierras and Andes rose after the Flood by isostatic rebound. [Baumgardner, 1990a; Austin et al., 1994]
* The main difficulty of this theory is that it admittedly doesn't work without miracles. [Baumgardner, 1990a, 1990b] The thermal diffusivity of the earth, for example, would have to increase 10,000 fold to get the subduction rates proposed [Matsumura, 1997], and miracles are also necessary to cool the new ocean floor and to raise sedimentary mountains in months rather than in the millions of years it would ordinarily take.
* Baumgardner estimates a release of 1028 joules from the subduction process. This is more than enough to boil off all the oceans. In addition, Baumgardner postulates that the mantle was much hotter before the Flood (giving it greater viscosity); that heat would have to go somewhere, too.
* Cenozoic sediments are post-Flood according to this model. Yet fossils from Cenozoic sediments alone show a 65-million-year record of evolution, including a great deal of the diversification of mammals and angiosperms. [Carroll, 1997, chpts. 5, 6, & 13]
* Subduction on the scale Baumgardner proposes would have produced very much more vulcanism around plate boundaries than we see. [Matsumura, 1997]
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