Summary
The hypothesis is developed that convection takes place continuously in the upper mantle and episodically also in the lower mantle. The reason for the latter assumption is seen in the temperature dependence of the viscosity. By radioactive heating of the lower mantle the viscosity gradually decreases until the critical Rayleigh number is achieved. The lower mantle convection initiated in this way, however, disappears after sufficient heat has been transferred to the exterior. This heat transfer becomes evident by an increase of igneous and tectonic activities in the crust.
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ZIPE Contribution No. 317.
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Walzer, U. A convection mechanism for explaining episodicity of magmatism and orogeny. PAGEOPH 112, 106–117 (1974). https://doi.org/10.1007/BF00875924
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DOI: https://doi.org/10.1007/BF00875924