Archaean drips

摘要

Earth is continuously being heated up by the radioactive decay of elements in its interior. Yet, at the same time, it is cooling down by mantle convection, and the cooling process is dominant at present. Mantle convection is sometimes referred to as Earth’s heat engine because it is the driver of modern plate tectonics — the movement and interaction of the lithospheric plates that make up Earth’s strong outermost crust and mantle. However, it is unclear how much hotter Earth was in the past and how long ago modern plate tectonic processes were operating. Writing in Nature Geoscience, Johnson and colleagues1 use thermodynamic and geodynamic numerical models to explore the tectonics of crust production and destruction in the context of a hot Archaean mantle. They show that the base of thick crust dripped into the mantle, rather than being drawn down in slabs as observed today.