Evidence of 4-billion-year-old subduction points to an early start for modern-Earth geology.
"Minerals preserved within ancient grains of rock, like flies within amber, have provided the earliest hint of plate tectonics on Earth. The minerals suggest that subduction — the process by which one tectonic plate slides beneath another — may have been active more than 4 billion years ago."
http://www.nature.com/news/2008/081126/full/news.2008.1256.html