Question

Which of the following statements describes the development of the geologic time scale?

Epoch
Era
Eon
Period

Answer 1

The geologic time scale is divided into several hierarchical units: eons, eras, periods, and epochs. Here’s a brief description of each:

1. **Eon**: This is the largest division of geologic time, covering billions of years. The Phanerozoic is one of the most well-known eons that includes the current geological time.

2. **Era**: This is the next subdivision of time following an eon. Eras can last tens to hundreds of millions of years. The Phanerozoic Eon is divided into three eras: Paleozoic, Mesozoic, and Cenozoic.

3. **Period**: A period is a division of an era, lasting tens of millions of years. Each era is made up of several periods, such as the Jurassic Period in the Mesozoic Era.

4. **Epoch**: The epoch is a subdivision of a period, lasting millions of years. For example, the Holocene is an epoch within the Quaternary Period.

In summary, the geologic time scale is organized in this hierarchical order: Eon > Era > Period > Epoch. Each level represents a decreasing length of time.