Plate tectonics has played a major role in the Earth’s evolution, both in the cooling of the planetary interior, and, it is widely argued, the maintenance of liquid water and life at the surface. But was the Earth always like this? The answer to this question is most likely to lie in relicts of the early Earth’s surface, preserved in Archean greenstone belts and found in almost all the cratons. In this talk, I compare field relations in the 3.5 – 3.2 Ga Barberton Greenstone Belt (BGB) in South Africa and Eswatini with the active New Zealand subducting plate-boundary zone. I show that there are remarkable similarities in structure and stratigraphy, with many of the distinctive features of convergent plate margins, and I argue that the simplest explanation is that plate tectonics was fully active in the Paleoarchean, generating great earthquakes on the subduction megathrust and growth folds and major low angle thrusts in the overlying accretionary prism and subsequent continental collision.

Oceania in the SW Pacific may provide us with the closest modern example of the surface of the Paleoarchean Earth, forming a water world with active volcanoes, back-arc spreading and small continental landmasses along a subducting plate boundary with local continental collision. In fact, the eruption of boninites here in the back-arc region may be a direct analogy for the typical komatiitic volcanism in the early Earth. The explosive eruption of Hunga Volcano near Tonga in 2022 could even provide clues to the origin of life, suggesting that life was born out of the extreme violence of plate tectonics, a far cry from Darwin’s benign and warm little pond!