Driving forces of the North American plate
By: Dan Weihrauch
Abstract:
A major question that is present today in Geosciences is the mechanisms of plate
movements. The idea of plate tectonics, developed in the 1960’s, set forth the basic
framework of plate movement. In my seminar I wish to focus on the North American plate
and the dynamics of its movement. There are two basic hypotheses or models of movement
that are being investigated. The first of these two models is convecting mantle in contact
with the base of the North American craton moving the continent. The second model of
motion deals with thermal evolution of the oceanic lithosphere which results in ridge push
forces. The validity of these two models has been investigated through the interpretation of
deformation within the North American plate.
Fig. 1 Cross section of Earth showing dynamic processes involved in plate tectonics from
http://www.solarviews.com/eng/earthint.htm
Fig. 2 Diagram A depicts a cartoon of the roots of the North American continent that is
being moved by ridge push forces, and diagram B depicts the continent being moved by
convective flow (Bokelmann, 2002).
Fig. 3 Comparison of ridge torque (solid arrows) and absolute motion of plates (dashed
arrows) from Richardson, 1992.
References Cited
Bokelmann, G.H.R., 2002, Convection-driven motion of the North American craton:
Evidence from P-wave anisotropy: Geophysical Journal Inernational, v. 148, p. 278287.
Bokelmann, G.H.R., 2002, Which forces drive North America?: Geology, v. 30, p.10271030.
Bokelmann, G.H.R., and P.G. Silver, 2002, Shear stress at the base of the lithosphere:
Geophysical Research Letters, v. 29, p. 1091-1095.
Forsyth, D.W., and Uyeda S., 1975, On the relative importance of driving forces of plate
motion: The Geophysical Journal of the Royal Astronomical Society, v. 43, p. 163200.
Richardson, R., 1991, North American plate dynamics: Journal of Geophysical Research, v.
96, p. 12,201-12,223.
Richardson, R., 1992, Ridge Forces, Absolute Plate Motions, and the Intraplate Stress Field:
Journal of Geophysical Research, v. 97, p. 11,739-11,748.