Strange rock formations beneath the Pacific Ocean could change our understanding of early Earth

Our world may seem fragile, but Earth has been around for a very long time. If we ventured far back into the past, would we reach a time when it looked fundamentally different?

The answer lies in some of the earliest extensive relics of Earth's surface, found in a remote corner of southern Africa's highveld—a region known to geologists as the Barberton Greenstone Belt. The geological formations in this region have proved difficult to decipher, despite many attempts. But our new research has shown the key to cracking this code lies in geologically young rocks laid down on the seafloor of the Pacific Ocean off the coast of New Zealand.

This has opened up a new perspective on what our planet looked like when it was still young. Our work began with a new, detailed geological map (by Cornel de Ronde) of part of the Barberton Greenstone Belt. This has revealed a fragment of the ancient deep seafloor, created some 3.3 billion years ago. There was, however, something very strange about this seafloor, and it has taken our study of rocks laid down in New Zealand, at the other end of the Earth's long history, to make sense of it. We argue that the widely held view of the early Earth as a hotter place, free of earthquakes and with a surface so weak it was unable to form rigid plates is wrong.

Credit: NASA, CC BY-SA Read more

This sketch profile through the New Zealand subduction zone shows how the bedrock in the shallow shelf region is sliding down into deeper water, where huge blocks pile up on top of each other. Credit: Simon Lamb, CC BY-SA Read more

This detail of a new map by Cornel de Ronde of the Barberton Greenstone Belt shows jumbled rocks with the remains of underwater landslides consisting of huge slide blocks. We think it is the inevitable consequence of one tectonic plate sliding beneath another in a subduction zone, periodically rocked by great earthquakes. Credit: Cornel de Ronde, CC BY-SA Read more