U. Walzer et R. Hendel, TECTONIC EPISODICITY AND CONVECTIVE FEEDBACK MECHANISMS, Physics of the earth and planetary interiors, 100(1-4), 1997, pp. 167-188
The evolution of the Earth is characterized by irreversible processes:
radioactive decay of the major heat-producing elements, thermal conve
ction and chemical segregation. The prevailing heating from within and
the temperature dependence of the viscosity are essential for thermal
convection. In the present paper, the chemical and thermal evolution
of the mantle and the generation of the continent material are represe
nted by a two-dimensional and finite-difference Boussinesq convection
model. We have incorporated the above-mentioned principal features in
this model, a geochemical paper by Hofmann (1988, Earth Planet. Sci. L
ett., 90: 297-314) constituting our starting point for the distributio
n of the radionuclides. The concentration of the radionuclides and the
viscosity are functions of the location and time developing according
to our system of differential equations. Although the real Earth is a
much more complex system, we have dared to make a comparison with obs
erved geophysical and geological data; we obtain a depleted upper mant
le and acceptable values for the heat flow on the surface of the Earth
as well as for the distribution of temperature, viscosity and of the
velocity of creep in the mantle. The ups and downs of the convective v
igour of the model roughly resemble the supercontinental cycles, the w
orld-wide distribution of mineral dates in time, the sea-level variati
ons and the variations of a number of geochemical parameters. (C) 1997
Elsevier Science B.V.