Related Clues:

• The Phanerozoic, e.g., in geology
• Period longer than a 12-Down
• Massive span
• Geologic time measure
• The Hadean, the Archean and the Proterozoic, e.g
• **Ages and ages (2 and 3)
• Earth's longest time divisions, geologically
• Astronomical time periods
• Number two in team running for a long time
• Collection of eras
• Long unit of time
• Extremely long times
• Very long stretches of time
• One's embarrassed for ages
• Word that's sometimes an exaggeration