  Energy for Geodynamics: Mantle Decompression Thermal-Tsunami A New Method of Deep-Earth Energy Transport |
J. Marvin Herndon (2006) Current Science, Vol. 90, No. 12, pp. 1605-1606 (click for pdf)
Summary
Previously in geophysics,
only three heat transport processes have been considered: conduction,
radiation, and convection or, more generally, buoyancy-driven mass
transport. As a consequence of whole-Earth decompression dynamics
(click for pdf),
J. Marvin Herndon adds a fourth, called
mantle decompression thermal-tsunami, which may emplace heat at the base
of the crust from a heretofore unanticipated source.
It is known through experience in deep mines and with bore-holes that temperature increases with depth in the crust. For more than half a century geophysicists have made measurements to determine the Earth’s heat loss and have found that the loss is greater than the heat currently produced by the decay of radioactive elements. This has led to speculation that some of the heat is derived from a yet unidentified heat source.
In the brief communication published in Current Science (click for pdf), Herndon discloses a heretofore unanticipated heat transport mechanism and heat source capable of emplacing heat at the mantle-crust-interface at the base of the crust.
One of the consequences of Earth formation as a giant, gaseous, Jupiter-like planet, as described by whole-Earth decompression dynamics, is the existence of a vast reservoir of energy, the stored energy of protoplanetary compression, available for driving geodynamic processes related to whole-Earth decompression. Some of that energy, Herndon suggests, is emplaced as heat at the mantle-crust-interface at the base of the crust through the process of mantle decompression thermal-tsunami.
As the Earth decompresses, heat must be supplied to replace the lost heat of protoplanetary compression. Otherwise, decompression would lower the temperature, which would impede the decompression process.
Heat generated within the core from actinide decay and/or fission or from radioactive decay within the mantle may enhance mantle decompression by replacing the lost heat of protoplanetary compression. The resulting decompression, beginning as low as at the bottom of the mantle, will tend to propagate throughout the mantle, like a tsunami, until it reaches the impediment posed by the base of the crust. There, crustal rigidity opposes continued decompression, pressure builds and compresses matter at the mantle-crust-interface, resulting in compression heating. Ultimately, pressure is released at the surface through volcanism and through secondary decompression crack formation and/or enlargement.
Mantle decompression thermal-tsunami, as outlined above, poses a new explanation for a portion of the internal heat being lost from the Earth. It may prove as well to be a significant energy source for earthquakes and volcanism, as these geodynamic processes appear concentrated along secondary decompression cracks.
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