A self-consistent 2D model of mantle convection with a floating continent
V. P. Trubitsyn, and V. V. Rykov
Schmidt United Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Abstract
[1] The mantle is modeled by a viscous fluid filling a horizontally elongated
2D region with an aspect ratio of 10:1. A model with Ra = 10
6 is
constructed on a 200
80 mesh. Developed nonsteady-state thermal
convection including narrow downwellings and upwellings sets in, with
mantle flow velocities ranging from 1 to 10 cm/yr. Then, at a certain
moment, a continent floating on the mantle is introduced into the model.
The continent is modeled by a thin long plate of a thickness of 0.03 and a
length of 2.0 relative units with respect to the mantle thickness, which
corresponds to dimensional values of 90 and 6000 km, respectively. To
demonstrate mantle heating beneath continent, the latter is positioned at
the coldest place of the mantle where downgoing flows dominate at the
moment chosen. The evolution of the mantle-continent system is found
from numerical solution of equations governing the momentum, mass, and
heat transfer in viscous fluid and rigid continent. The problem is rigorously
formulated, a self-consistent method is given for the solution of coupled
integrodifferential equations, and a technique of their numerical
implementation is described. The continent remains virtually immobile
during a long time (about 500 Ma), but the mantle flow pattern
dramatically changes, which results in suppression of cold mantle
downwellings under the continent and their gradual replacement by hot
upwellings. Afterwards the viscous drag of mantle flows begins to move the
continent at a variable velocity averaging about 1 cm/yr. The mantle flow
pattern and continent velocity constantly changes under the action of
mechanical coupling and thermal interaction between the mantle and
moving continent. After a time of about
1.5 109, when the continent
has traveled over a distance of about 15000 km, it arrives at a place where
several cold mantle downwellings concentrate. Then the continent velocity
sharply decreases, and the continent continues its motion in either primary
or opposite direction, depending on the general mantle flow pattern. The
results of the numerical experiment can be used for the analysis of
mechanism responsible for the motion of Eurasia-type continents,
origination and ascent of plumes, and geodynamic processes in the
subcontinental mantle.
Received 15 May 1998; published 20 July 1998.
Keywords: mantle convection, floating continent, numerical simulation, evolution of the mantle-continent system.
Citation: Trubitsyn, V. P., and V. V. Rykov (1998), A self-consistent 2D model of mantle convection with a floating continent, Russ. J. Earth Sci., 1, No.1, 1-10, doi:10.2205/1998ES000001.