Related Clues:
- Geologist’s time unit
- Mighty long stretch
- A billion years, as a unit
- Geological time measure
- Time period hidden in "Come on, man!"
- Geological span of 1 billion years
- Section of geological history
- Incredibly long geological span
- Geological span of many, many years
- Geologic time frames
- A real long time
- Period in the geologic time scale
- Very long time spans
- Geologist’s time period
- Long period in Spain, working