archaean
/ɑrˈkiːən/
adjective
- Relating to the earliest known period of Earth's history, from about 4 billion to 2.5 billion years ago, before the Proterozoic eon.
- The Archaean eon saw the formation of the first continents.
- Fossils from the Archaean era are extremely rare.
- Scientists study Archaean rocks to understand early Earth conditions.
noun
- The Archaean eon; the geological time period from about 4 billion to 2.5 billion years ago.
- Geologists divide the Archaean into several eras.
- The Archaean lasted for over a billion years.
- Life first appeared during the Archaean.