Geologyhttp://doi.org/htv (2012)

Credit: © GSA

Some continental rocks were formed during the Archaean eon, but it is unclear whether modern-style plate tectonics operated on a younger, hotter Earth. Geodynamical modelling indicates that any subduction occurring more than 2.5 billion years ago would have been short-lived and episodic.

Jean-François Moyen at the Université Jean-Monnet, France, and Jeroen van Hunen at Durham University, England, used numerical models to simulate the style of plate tectonics that might have existed during the Archaean. Under the assumption of a mantle that is 200 K warmer than today, the simulations indicate that the tectonic plates had a thicker crust than today, whereas the lithospheric portion of the mantle was thinner. The hot underlying mantle was also weaker, and so provided less support for the sinking slabs. Overall, slabs broke off the subducted plate more frequently, which prevented the formation of long-lived subduction systems like those that characterize Earth today. Instead, the simulated subduction systems quickly halted and re-initiated within a few million years. This progression is recorded in the geologic record by the succession of subduction and non-subduction-related volcanic rocks in areas such as the Canadian Superior Province.

The researchers suggest that rather than appearing suddenly, the Earth's system of plate tectonics matured over many millions of years, becoming increasingly stable through time.