A period of 1,000,000,000 years, or one billion years, is commonly called an eon in the fields of geology and astronomy.
An eon is the largest division of geologic time. It represents an extremely long duration in the Earth's history and is often used to describe events that occurred over vast timescales. For example, the Phanerozoic Eon is the current eon and represents the period of time during which abundant animal life has existed.
Here's a breakdown of the geological timescale, showing how eons fit into the hierarchy:
- Eon: The largest division of geologic time (1,000,000,000 years).
- Era: A subdivision of an eon.
- Period: A subdivision of an era.
- Epoch: A subdivision of a period.
- Age: A subdivision of an epoch.
Therefore, when discussing very long timeframes in Earth's or the universe's history, "eon" is the generally accepted term for a period of one billion years.
