Posted by: paulgarner | September 10, 2009

Rapid sea floor spreading and glacial mega-lineations

It’s been a busy week — not much opportunity for blogging — but I’ve just got time to mention a couple of items from the recent literature.

First, new simulations described in the August edition of Geology suggest that oceanic crust was being produced at higher rates in the middle to late Cretaceous (~70-90 mm per year) compared with the present day (Seton et al 2009). As a consequence, the average age of the Cretaceous sea floor was younger than today. The lower density of this young ocean crust led to a reduction in the relative volume of the ocean basins, thus displacing ocean water onto the continents. When the pulse of rapid sea floor spreading ended, the oceanic lithosphere cooled, subsided, and global sea level fell. Now imagine, if you will, a time when sea floor spreading rates were much, much higher than the present day, not by tens of millimetres per year, but by orders of magnitude. Catastrophic plate tectonics leading to global flooding of the continents, anyone?

Second, a paper in Nature Geoscience reports mega-scale glacial lineations from the bed of a West Antarctic ice stream that are indistinguishable from those found associated with ancient examples, such as the palaeo-bed of Dubawnt Lake ice stream in northern Canada (King et al 2009). The evidence indicates that these subglacial bedforms are associated with fast flowing ice and evolve rapidly (on decadal timescales). For creationists, this has interesting implications for the interpretation of relict landforms associated with the rapid ice advance following the global Flood.

References

King E. C., Hindmarsh R. C. A. and Stokes C. R. 2009. Formation of mega-scale glacial lineations observed beneath a West Antarctic ice stream. Nature Geoscience 2(8):585-588.

Seton M., Gaina C., Müller R. D. and Heine C. 2009. Mid-Cretaceous seafloor spreading pulse: fact or fiction? Geology 37(8):687-690.

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