Abstract

This paper reviews Canadian contributions to global geodynamics during the International Geodynamics Project, including: the decisive demonstration that great earthquakes can excite the Chandler wobble; the use of inland Earth-tide observations to infer the tides in the open ocean; a new upper limit on the temporal decrease of the gravitation constant, set by the absence of tensional features on Mercury, the refinement of Earth models, particularly of the lower mantle and core, using array-recorded multiply-reflected core phases; development of the mathematical machinery for modelling postglacial rebound on a viscoelastic Earth (with self-gravitation and redistribution of meltwater), the evolution of sedimentary basins, and the migration of phase transitions in depth in response to surface loading; discovery of a high degree of organization in lithospheric plate geometry over the entire Phanerozoic, and its interpretation in terms of an evolving mantle-wide convection pattern; incorporation of whole-mantle convection and a vis-cosity profile in a model for the Earth's thermal history; resolution of the 'core paradox' by improved estimates of the Gruneisen parameter using liquid metals theory; pioneering theoretical studies of long-period oscillations of the rotating liquid core, and development of a high-precision gravimeter to search for such modes and the information they should provide on the thermal state of the core; palaeomagnetic confirmation of the centred dipole hypothesis; and proof that laminar precession-driven flow in the core is incapable of sustaining the geomagnetic dynamo.

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