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 |
|---|---|---|---|
| c. 950 | — | ? | S of Jefferson (South Cinder Peak) · Sidereal: Varve Count |
| 4,500 BCE ± 50 years | — | ? | SSE of Jefferson (Forked Butte) · Sidereal: Varve Count |
Data: Global Volcanism Program, Smithsonian Institution (#322020)