Eruption history
VEI – Volcanic Explosivity Index: 0 = lava outpouring, 4 = like Eyjafjallajökull 2010, 6 = like Pinatubo 1991, 7 = like Tambora 1815. The scale is logarithmic – each step is about 10 times more material.
| Start | End | VEI | Vent and dating |
|---|---|---|---|
| 439 ± 108 years | — | 2 | NW of North Sister (Collier Cone) · Isotopic: 14C (calibrated) |
| 40 ± 202 years | — | 2 | NW of North Sister (Four-in-One Cone) · Isotopic: 14C (calibrated) |
| c. 50 BCE | — | 3 | N & S flanks of South Sister (Devils Hill) · Isotopic: 14C (uncalibrated) |
| c. 350 BCE | — | 4 | SW flank of South Sister (Rock Mesa) · Isotopic: 14C (uncalibrated) |
| c. 800 BCE | — | 2 | North of North Sister (Yapoah Cone) · Correlation: Tephrochronology |
| 7,350 BCE ± 2,700 years | — | 2 | WNW of North Sister (Sims Butte) · Correlation: Tephrochronology |
Data: Global Volcanism Program, Smithsonian Institution (#322070)