The progression of a planet from a pre-plate tectonics, to a plate-tectonic regime, has been shown to be very sensitive to system parameters, such as thermal state and the specific rheology. Whilst generally it has been shown that cold-interior high-Rayleigh number convection (such as on the Earth today) favours plates, due to the ability of the interior stresses to couple with the lid, a given system may or may not have plate tectonics depending on its initial conditions. This has led to the idea that there is a strong-history dependence to tectonic evolution – and the details of tectonic transitions, including whether they even occur, may depend on the early history of a planet.
However, intrinsic convective stresses are not the only dynamic drivers of early planetary evolution. Early planetary geological evolution is dominated volcanic processes, and impacting. These have rarely been considered in thermal evolution models. Recent models exploring the details of plate tectonic initiation have explored the effect of strong thermal plumes or large impacts on surface tectonism, and found that these ‘primary drivers’ can cause a transition from a stagnant-lid state to an active lid, and, in some cases, over-ride the pre-configuration set by initial conditions.
The only detailed planetary record we have of the development comes from Earth, and is restricted by the limited geological record of its earliest history. Many recent estimates have suggested an origin of plate tectonics at ca. ~3.0Ga, inferring a somewhat monotonic transition from pre-plates to a somewhat modern plate tectonic regime around that time. However, both numerical modelling, and the geological record itself, suggest a strong non-linearity in the dynamics of the transition, and it has been noted that the early history of Archaean greenstone belts and TTGs may be one of failed subduction.
This talk will explore the history of subduction failure on the early Earth, and couple these with insights from numerical models of the geodynamic regime at the time.