|A zircon crystal estimated to be 4.4 billion years old|
John Valley, University of Wisconsin
Penetrating so many secrets, we cease to believe in the unknowable. But there it sits, nevertheless, calmly licking its chops.
― H. L. Mencken
|Genesis Rock from the moon.|
The Genesis Rock, collected by Apollo 15 astronauts during their moon landing, has been dated at 4.46 billion years. Although it originated on the Moon, it is one of the oldest known rocks.
Scientists hypothesize that the Earth began orbiting the sun about 4.6 billion years ago. As a molten protoplanet, the Earth needed a cooling period before a rocky crust was formed that was cool enough to support carbon-based organisms. It cooled from its molten state to solid earth. Terra firma is Latin phrase meaning solid earth. Terra translates to earth. Firma translates to solid.
"You're on Earth. There's no cure for that."The dating of the Jack Hills crystal suggests that by its 200-millionth birthday, the Earth had a rocky crust.
— Samuel Beckett
Chemical hints in the Isua sediments found on the southwestern coast of Greenland suggest life existed as early as 3.8 billion years ago.
"What are men to rocks and mountains?"
— Jane Austen, Pride and Prejudice
- 4.4 Billion-Year-Old Crystal Is Oldest Piece of Earth, Elizabeth Landau, CNN, 25 February 2014.
- 4.4 Billion-Year-Old Crystal Is Oldest Piece of the Earth’s Crust, Allison Eck, PBS, 24 Feb 2014
- At 4.4 Billion Years Old, Oz Crystals Confirmed As World's Oldest, NPR, Nell Greenfieldboyce, 24 February 2014.
- Oldest dated rocks, Wikipedia.
- Terra Firma, Wikipedia.
- The Isua Rocks, Douglas Page, 2000.