Supervolcanic eruptions — those with a Volcanic Explosivity Index of 8 or higher — are among the most powerful geological events on Earth. The Toba eruption approximately 74,000 years ago is believed to have reduced the global human population to as few as 10,000 individuals, nearly driving Homo sapiens to extinction.
A Yellowstone-scale eruption today would immediately devastate North America under metres of ash, but the greater threat is the volcanic winter that follows — years of reduced sunlight causing global crop failures, ecosystem collapse, and societal breakdown far beyond the eruption zone.
Unlike asteroid impacts, supervolcanic events cannot be prevented or deflected. Monitoring provides some warning (days to months), but no mitigation is possible at civilisational scale. The Yellowstone caldera has erupted three times in the past 2 million years — the question is not if but when.