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| Mount St. Helens Timeline |
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| 40,000-35,000 years ago |
| Date |
| Eruptive Stage |
| Date Of Eruptive Period |
| Eruptive Period |
| Products Emitted |
| Ape Canyon |
| tephra pyroclastic flows lahars |
| 35,000 to 20,500 years ago |
| Dormant |
| Dormant |
| 20,500 to 19,200 years ago |
| Cougar |
| tephra pyroclastic flows domes avalanches lava flows |
| 19,200 to 13,000 years ago |
| Dormant |
| Dormant |
| 13,000 to 10,500 years ago |
| Swift Creek |
| tephra pyroclastic flows lahars domes |
| 4,000 years ago to present |
| Spirit Lake |
| 1800 to 1900 |
| avalanche lateral blast blast deposits lahars pyroclastic flows tephra lava domes |
| Spirit Lake |
| Modern |
| 1980 |
| Goat Rocks |
| tephra lava dome lava flows lithic ash |
| 4,000 years ago to present |