Sensitivity experiments on True Polar Wander

Marianne Greff-Lefftz (1) , Jean Besse (1)

1 IPGP - Institut de Physique du Globe de Paris

Using sensitivity experiments based on the position of subductions and of superplumes, we derive models for the temporal evolution of 3-D mass anomalies in the mantle and compute the associated inertia perturbations and polar wander. We show that although the large length-scale mantle dynamics during the Earth's history may have been dominated by coupled supercontinent-superplume cycles, subductions alone are sufficient to trigger major True Polar Wander (TPW) episodes, or rotation of the whole lithosphere and mantle with respect to the Earth's rotation axis. We present two examples. We speculate that the distribution of continents with respect to the equator on the Earth's surface is driven by episodic subductions during the Wilson cycle: alternating fast subduction girdles around continents and upwellings during the divergence phases, with both reduced or stopped subductions activity around continents and moderate inter-continental subductions during the convergence phases, lead to successive equatorial or polar distributions of continents, both configurations being separated by strong episodes of TPW. Finally, using plate reconstructions and geologic maps, over the period 1100-720 Ma, the period of amalgamation and destruction of the Rodinia supercontinent, we explain with our model the observed large eastward/westward and poleward/equatorward motions of the rotation axis.

Mots clés: Earth rotation variations; subduction; mantle plumes; supercontinent

Domaines: Planète et Univers [physics]

Marianne Greff-Lefftz, Jean Besse. Sensitivity experiments on True Polar Wander. Geochemistry, Geophysics, Geosystems, 2014, 15, pp.4599-4616. ⟨10.1002/2014GC005504⟩. ⟨insu-03581056⟩