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Episodic Tectonics

Episodes of layering?

Because of the effect of phase transformations within the transition zone of the mantle, it is possible that the mantle went through episodes in which convection operated in two separate layers. The breakdown of such layering is illustrated here. The model starts off layered, and the top layer cools until it is dense enough to break through the phase transformation barrier. The cool (blue) upper fluid then drains rapidly to the bottom, and is replace by hot (red) fluid.

Such a breakdown might have been rapid, with dramatic consequences at the earth’s surface: massive volcanic eruptions and kilometers of uplift or subsidence.

See:
Davies, G. F., Penetration of plates and plumes through the mantle transition zone, Earth Planet. Sci. Lett., 133, 507-516 (1995)
Davies, G. F., Punctuated tectonic evolution of the earth, Earth Planet. Sci. Lett., 136, 363-379 (1995)

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Notes: Last modified: Wed, 19 Dec 2001