Related Clues:
- Earth science measures
- Volcanoes develop over them
- Moderate, not initially, frequently
- Figure seen on middle of sofa regularly
- Happening many times
- Millions and millions of years
- Extremely long time divisions
- Very long time periods
- Many, many times
- Much more than 60-Across
- Astronomer's measures
- Rarely opposite
- Eternity, so to speak
- Massive time periods
- Plenty of times