Archaean seafloors shallowed with age due to radiogenic heating in the mantle

摘要

Given the scarcity of geological data, knowledge of Earth's landscape during the Archaean eon is limited. Although the continental crust may have been as massive as present by 4 Gyr ago, the extent to which it was submerged or exposed is unclear. One key component in understanding the amount of exposed landmasses in the early Earth is the evolution of the oceanic lithosphere. Whereas the present-day oceanic lithosphere subsides as it ages, based on numerical models of mantle convection we find that higher internal heating due to a larger concentration of radioactive isotopes in the Archaean mantle halted subsidence, possibly inducing seafloor shallowing before 2.5 Gyr ago. In such a scenario, exposed landmasses in the form of volcanic islands and resurfaced seamounts or oceanic plateaus can remain subaerial for extended periods of time, and may have provided the only stable patches of dryland in the Archaean. Our results therefore permit a re-evaluation of possible locations for the origin of life, as they provide support to an existing hypothesis that suggests that life had its origins on land rather than in an oceanic environment.