The Toba supervolcano erupted 74,000 years ago in what is now Indonesia, spewing roughly 2,800 cubic kilometers of ash and rock into the atmosphere. That’s enough material to bury the entire state of Texas under three feet of volcanic debris. Turns out, this wasn’t just a bad day for anyone living nearby—it might have nearly wiped out our entire species.
Human populations crashed to somewhere between 3,000 and 10,000 individuals, according to genetic bottleneck studies. We went from scattered groups across Africa and Asia to basically an endangered species list candidate. The sky turned dark for years, temperatures plummeted by 3-5 degrees Celsius globally, and the resulting volcanic winter lasted potentially a decade.
That’s the nightmare scenario scientists keep gaming out when they talk about supervolcanic eruptions.
When Yellowstone Decides It’s Had Enough of Being a Tourist Attraction
Here’s the thing about Yellowstone: it’s not a mountain that might explode. It’s a 55-kilometer-wide caldera sitting atop a magma chamber the size of Los Angeles, and it’s overdue by about 40,000 years if you trust the 600,000-year eruption cycle. The last time it blew—640,000 years ago—it covered half of North America in ash. Rhinoceroses in Nebraska suffocated. Ancient camels in Kansas choked on particulates.
Modern civilization would fare considerably worse.
A Yellowstone eruption would dump a layer of ash 10 feet thick across Wyoming, Montana, Idaho, and Colorado within days. Everything within a 100-kilometer radius gets obliterated immediately—not by lava, but by pyroclastic flows traveling at 700 kilometers per hour with temperatures exceeding 400 degrees Celsius. Then the real problems start. Ash clouds circle the globe within weeks, blocking sunlight and dropping global temperatures by an estimated 10 degrees Celsius for several years. Agriculture collapses across entire continents.
Wait—maybe that’s not even the worst part.
The sulfur dioxide released would dwarf anything we’ve seen in recorded history. Mount Pinatubo in 1991 ejected 20 million tons of sulfur dioxide and cooled the planet by 0.5 degrees for two years. A supervolcano could release 100 times that amount, creating sulfuric acid aerosols that linger in the stratosphere for a decade. Monsoons fail across Asia. The Amazon rainforest dries up. Ocean circulation patterns shift unpredictably.
The Mathematics of Civilizational Collapse That Nobody Wants to Calculate
Two billion people depend on monsoon rains for food production. Another billion rely on crops grown in regions that would see growing seasons cut by 40-60% under volcanic winter conditions. Michael Rampino at New York University estimates that a Toba-scale eruption today could trigger famines affecting 90% of the global population within eighteen months. The supply chain disruptions from COVID-19 would look like a minor inconvenience by comparision.
Infrastructure fails in ways we don’t typically imagine. Ash conducts electricity when wet, causing power grid collapses across entire regions—exactly what happened in Washington state when Mount St. Helens erupted in 1980, and that was a relatively tiny eruption. Jet engines ingest volcanic ash and shut down mid-flight; after the 2010 Eyjafjallajökull eruption in Iceland, European airspace closed for six days, stranding 10 million passengers. Scale that up globally for months or years.
Financial markets would crater before the ash even settled. The 2008 financial crisis wiped out $2 trillion in global wealth. A supervolcano could eliminate $20-40 trillion according to some economic models, making the Great Depression look like a quarterly earnings dip.
But here’s what keeps volcanologists up at night: we have no idea when the next one hits. The geologic record shows roughly 20 supervolcanic eruptions in the last 100 million years—about one every 5 million years on average. Toba happened 74,000 years ago. Yellowstone last went 640,000 years ago. The Campi Flegrei caldera near Naples, Italy, showed signs of unrest in 2023, with over 1,100 earthquakes recorded in a single month and ground uplift of 20 centimeters per year.
Turns out we’re remarkably unprepared for low-probability, high-impact volcanic events. The United Nations Office for Disaster Risk Reduction published a report in 2022 warning that volcanic winter scenarios receive essentially zero funding compared to climate change research, despite potentially comparable impacts. We’ve built entire civilizations in volcanic shadow zones—Seattle sits 80 kilometers from Mount Rainier, Tokyo is 130 kilometers from Mount Fuji, Naples is basically on top of Vesuvius and Campi Flegrei.
Maybe that’s the most unsettling part: we know exactly what will happen when a supervolcano erupts. We’ve studied the geological evidence, run the climate models, mapped the ash deposits from previous eruptions. We just have no idea when, and almost no meaningful preparation for if. The food stockpiles don’t exist. The agricultural backup plans don’t exist. The international coordination mechanisms definately don’t exist.
Three-quarters of a century ago, Toba nearly ended us. Next time, we’ll have more people, more infrastructure, more interconnected supply chains—and potentially, even less margin for error.
