Russian Journal of Earth Sciences
Vol. 6, No. 6, December 2004
Numerical analysis of geodynamic evolution of the Earth based on
a thermochemical model of mantle convection: 3-D model
V. D. Kotelkin
Mechanical-Mathematical Faculty of the Moscow State University
L. I. Lobkovsky
P. P. Shirshov Institute of Oceanology, RAS
Abstract
Evolution of the Earth's mantle from a hot initial state
is modelled in the Boussinesq approximation within the framework of
a thermochemical model. The spatial dynamics of substance within a
spherical layer is illustrated by video records. Introduction of a
chemical component into intermittent (with regard for an
endothermic phase transition) thermal convection facilitates the
overcoming of the phase barrier, enhances nonlinearity of the
dynamic process, and promotes the formation of new cycles in the
evolutionary process. As a result, avalanches become more numerous
in the thermochemical variant and reduce to a regional scale;
therefore, it is more natural to associate them with Bertrand
(rather than Wilson) cycles. A basically new result of the
numerical modelling is that convection developing from an unstable
hot initial state gives rise to global mantle overturns (see
Animations 2, 3, 4) decaying with cooling material and remarkably
correlating with data of historical geology on Wilson cycles. The
inferred spatial patterns of overturns are represented by a single
funnel-shaped sink and a few uprising superplumes, accounting for
the origins of supercontinents, opening of oceans, and the
observed asymmetry of the planet.