| Answer | Crossword Clue |
|---|---|
| NEOCENE | Of a period of the earth's formation. |
| POLARCAP | Icy formation at either extremity of the Earth's axis |
| EON | Period in the earth's history |
| EON | Phanerozoic ... (current period in the earth's history) |
| PERMIAN | Period marked by the largest mass extinction in earth's history |
| NEOCENE | Period in Earth's history |
| AZOIC | .. Era: old name for Earth's pre-life period |
