Our planet coalesced some 4.54 billion years ago, but Earth’s oldest known rocks date back only to about 4 billion years. Older rocks must have existed, but they’ve been eroded away or were buried and transformed through metamorphism into unrecognizable form. A few may still lie in some remote Canadian or Siberian hillside, waiting to be recognized, but largely, the first 600 million years of Earth history constitutes our planet’s Dark Age.
