New Scientist informs us of the discovery that a piece of Earth’s crust has been found in Greenland, as dates back to at least 3.8 billion years. It’s significant because until recently, it was thought that continental plates had not formed until much later.
For reference, life is thought to have originated around 4 billion years ago (there are questionable fossilized unicellular organisms dating to 3.5 billion years ago). The oldest rock found so far is 4.04 billion years old, and tiny zircon crystals have been dated to 4.4 billion years ago. Earth itself is estimated to be 4.57 billion years old.