A VEI 8 eruption throws out more than a thousand cubic kilometres of material. None has happened in human history; the largest recent one, Tambora in 1815, was a smaller VEI 7 and still cooled the planet for a year. The risk from a supereruption is dominated by what the ash and sulfur do to the climate and harvests, not by the blast.
The tier rates the quality of the evidence, not how likely the event is.
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| Source | Statement | Kind |
|---|---|---|
| Toby Ord ↗ | 1 in 10,000 chance, per century, of an existential catastrophe from a supervolcanic eruption (his own estimate) | EXPERT ESTIMATE |
Expert estimates are personal judgements, not measurements, and experts disagree. This site never adds its own probabilities.
Caveat
Recurrence intervals are not a countdown: supereruptions are irregular and the system does not run on a clock. Unrest is common at calderas and almost never ends in an eruption; the live status above is the current picture.
Open the preparedness checklist for this scenario →
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| Eruption | When | VEI | Effect |
|---|---|---|---|
| Pinatubo, Philippines | 1991 | 6 | About 20 million tonnes of SO₂; global surface cooling of about 0.5 °C for roughly two years |
| Tambora, Indonesia | 1815 | 7 | Global cooling of roughly 0.4–0.7 °C; the 1816 'year without a summer', harvest failures from Ireland to China |
| Toba, Indonesia | ~74,000 years ago | 8 | Climate and human-population effects are debated; there is no agreed figure |
VEI is the Volcanic Explosivity Index; each step is about ten times more material, and VEI 8 means more than 1,000 km³ of erupted material. A VEI 8 eruption is roughly 1,000 times the volume of Pinatubo's VEI 6, so its effects cannot be read off these examples: they are what models and the geological record suggest.
Why this site shows no ash-fall map: a credible ash-thickness forecast needs the eruption size, vent height and the actual winds on the day, and the published scenarios differ widely. A made-up footprint would look more certain than the science is.