Supercontinent cycles, true polar wander, and very long-wavelength

Shijie Zhong
University of Colorado at Boulder
31 March 2010

This talk discusses the large-scale evolution of the Earth for the last 1 billion years, and possible physical mechanisms that control the evolution. The Earth's surface including seafloor and continents moves constantly at a slow rate in response to convective motions in the Earth's mantle. For the present-day Earth, while continents are scattered around on the surface, the convective structure within the mantle is predominated at a spherical harmonic degree 2. However, in the last 1 billion years, there are two episodes in which a supercontinent is formed as all the continents collide together and is later fragmented. Supercontinent formation and fragmentation are responsible for the most significant tectonic and volcanic events on the Earth. There is also evidence that the Earth may undergo a process of large-scale rigid body rotation, called true polar wander, during the supercontinent episodes. This talk will begin with an extensive review of relevant observations and inferences, and end with a physical mechanism of spherical harmonic degree-1 mantle convection to account for the diverse observations.

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