Alec Brenner on When Tectonic Plates First Moved

Alec Brenner explains how palaeomagnetic measurements reveal independent motion of the East Pilbara and Kaapvaal cratons about 3.5 billion years ago. The evidence moves the detection of relative plate motion much earlier and constrains models of early Earth tectonics. It rules out a permanently stagnant surface without establishing that modern plate tectonics already operated, and also informs questions about the core and atmosphere.