When did tectonic plates start moving?

The most exciting thing about this article is that I started reading it and then realized THAT I KNOW THE PERSON WHO DID THIS RESEARCH!! Rita is a graduate student at BU who I have worked with, and gone camping with, she was my TA for Mineralogy(!).

"Volcanic rocks found in the south Pacific spent at least 2.45 billion years on a journey into Earth's interior – and back again.

The finding could help narrow down when our planet's massive tectonic plates first started jostling with each other, which may have provided a crucial backdrop for life's early evolution.

About 20 million years ago, volcanic eruptions spewed out magma that cooled and solidified to form the basaltic rocks of Mangaia, one of the Cook Islands. There is some evidence that the eruptions also brought up remnants of ancient oceanic crust, which had been forced deep into the mantle long ago. This happens when one tectonic plate is pushed down underneath another – a process called subduction.

To work out the age of that recycled ancient crust, Rita Cabral of Boston University and her colleagues analysed the sulphur isotopes in Mangaia's basalt rocks...

Earth is the only planet in our solar system that has active plate tectonics – and the only place we know of that harbours life. "Many researchers think that the features associated with plate tectonics, such as hydrothermal vents, provided the nutrients and surfaces for the first life to form," says Cabral.

There is little consensus about when plate tectonics began, though. Rocks found in Greenland in 2007 suggest hydrothermal vents were present 3.8 billion years ago, just before life is thought to have originated. But it isn't clear when other crucial features of plate tectonics – particularly subduction – began."
For a more thorough discussion of this topic, specifically When did tectonic plates form? Check out this thorough and accessible review of the matter!