Highly read on geology.gsapubs.org in January

Plates of Earth's crust could have been sliding beneath one another (or subducting) as far back as 4.4 billion years ago — soon after the planet's crust formed.

Previous studies have estimated that subduction started anywhere between roughly 1 billion and 4 billion years ago. Simon Turner at Macquarie University in Sydney, Australia, and his colleagues studied rocks in northern Quebec, Canada, that are up to 4.4 billion years old. Trace elements in the rocks and the sequence in which the rocks are layered strongly resemble those formed along a modern-day subduction zone south of Japan, called the Izu-Bonin-Mariana arc.

The geochemical similarities suggest that the Canadian rocks were formed in a subduction environment, the authors say. They add that chemical reactions in deep-diving crustal slabs could have generated the organic molecules that fuelled the development of early organisms.

Geology 42, 139–142 (2014)