Journal of Petroleum Geology, Vol.12, No.1, pp. 5-28, 1989
©Copyright 2000 Scientific Press, Ltd.
A MODEL THAT QUANTITATIVELY EXPLAINS GEODYNAMICS: Mantle
convection, the geothermal gradient, sea-floor spreading, plate tectonics, the creation of
the continents and petroleum, and the nature of the terrestrial heat flow
A.A. Giardini* and C.E. Melton**
* Department of Geology, University of Georgia.
** Department of Chemistry, University of Georgia, Athens,
Ga. 30602. USA.
Abstract
A model is presented that traces quantitatively the history of
geodynamic processes, from the time of origin of the Earth to the present time. Initially,
the Earth underwent a slow, cool, homogeneous accretion, then a non-catastrophic formation
and melting of the core. Thereupon, the gravitational interaction of the Moon and core
produced a thermal power of about 1013watts. It is this power that creates the buoyant force for the upflow of
convection. The convection is shown to serve three functions: (1) the transference of heat
from the mantle base to the surface for radiation to space; (2) the uplift to the surface
and separation from the convection cycle of "incompatible" constituents; and (3)
the redistribution of heat from the mantle's base to its body by conductive transfer. The
"incompatible" constituents include continental, oceanic, atmospheric, petroleum
and radionuclide materials. They are stored initially in the asthenosphere region up to a
limiting capacity that ensures the thermal integrity of the lithospheric shell. The
capacity range is regulated by a periodic relief mechanism, namely, a controlled
penetration of the lithosphere and eruption of continental and other
"incompatible" material to the surface. The transfer of radionuclides to the
surface region acts to regulate the conductive thermal loss from the Earth's interior in
order to maintain a steady state. Mantle heat lost by removal of radionuclides is replaced
via conductive transfer from the hot, upflowing convection. The mechanisms of cooling in
the 400-km deep surface leg of the convection, the formation of the continents, and the
pattern of heat flow from the Earth's surface are analysed in detail. A thermodynamic
analysis of the convection cycle is presented, as well as detailed power analyses for the
various work functions that are involved in the convection. Values obtained for power
input and output of the convection are in agreement to within 2%.
