Remnants of Earth’s original crust preserve time before plate tectonics

Full-blown plate tectonics had late start, geochemical evidence suggests

Oldest rocks yet

CLASSIC ROCK  Rocks from an outcrop in northeastern Canada may have formed from material dating back more than 4.2 billion years ago. That’s older than the oldest rocks found on Earth’s surface today.

 J. O’Neil

Not all of the newborn Earth’s surface has been lost to time.