Diamond dirt shows continents started drifting three billion years ago.

Rough diamond with
sulfide inclusion.

Diamonds come from the oldest, deepest rock on earth and can pass billions of years before randomly being spit up in volcanic plumes.   Bits of sulfide dirt in some diamonds reveal the conditions down below when they were formed.   Slowly decaying isotopes in the diamond serve as a kind of clock. The clock shows that about 3.2 billion years ago the sulfide dirt found trapped in diamonds changed composition.  This appears to be when the first continental plates started sliding over and under each other, mixing up the deep mantle.  Science Daily News