You’ve probably heard the whispers, seen the headlines: Yellowstone. The name alone conjures images of a sleeping giant, a supervolcano capable of unleashing unimaginable power. Barely a month goes by without some new tremor or steam-driven explosion sending shivers down the spines of disaster preppers and news editors alike. Sometimes, it feels like the whole world is holding its breath, almost willing Yellowstone to blow.

But what’s the real story? Do the latest scientific findings bring good news or bad? Let’s dig into what a Yellowstone super-eruption could truly mean for our planet.

Peering Beneath the Surface: New Clues from Yellowstone

Recent research by the United States Geological Survey (USGS), published in Nature in January 2025, has given us an unprecedented look at what’s brewing beneath Yellowstone National Park. By meticulously mapping the electrical conductivity of the underground rocks, scientists were able to create a 3D picture of the magma reservoirs. Why electrical conductivity? Because molten rock is up to a thousand times more conductive than solid rock, making it relatively easy to pinpoint.

So, what did they find? The good news is that the magma isn’t one giant, unified pool filling a subterranean void. Instead, it’s mostly contained in pockets, making up a relatively small percentage (2-30%) of the surrounding hot, solid rock. Even better, these magma-hosting areas aren’t all connected, meaning a single, colossal eruption that empties everything in one go is unlikely.

The most intriguing revelation, however, points to where the next major eruption might be centered. The magma isn’t evenly distributed. A significant concentration — somewhere between 400 and 500 cubic kilometers of sticky, silica-rich rhyolite magma — is lurking beneath the northeast section of the Yellowstone Caldera, the massive crater left by the last super-eruption 630,000 years ago. This is a larger volume than what erupted in Yellowstone’s considerable Mesa Falls blast about 1.3 million years ago. Adding to this, hot basalt magma from deep within the Earth is continuously pumping heat into this region, keeping the rhyolite magma hot and steadily increasing its volume.

While this might sound alarming, remember that the magma is spread out. For a truly “super” eruption to occur, these pockets of molten rock would need to connect and pool together, accumulating enough volume to be expelled in one massive event. Nevertheless, the researchers behind the Nature paper suggest this area is the most probable location for the next significant outburst. The burning question remains: when?

Is a Super-Eruption “Overdue”?

Despite popular belief, a Yellowstone super-eruption is not overdue. The idea that it’s on a strict schedule is a misconception. Looking back at Yellowstone’s history, there have been three major eruptions: the Huckleberry Ridge eruption (around 2.1 million years ago), the Mesa Falls eruption (around 1.3 million years ago), and the Lava Creek outburst (630,000 years ago).

The average time between these three events is about 735,000 years. However, if we only consider the two truly “super” eruptions (those exceeding the 1,000 cubic kilometer threshold for ejected material), the return period is closer to 1.5 million years. Given this geological timeline, the next Yellowstone super-eruption could still be a very, very long time away. But make no mistake, it will happen eventually, and its impact will be immense, affecting not just the United States but the entire planet.

What a Super-Eruption Would Look Like

To understand what a future Yellowstone eruption might entail, we can look to its past. All previous super-eruptions shared common characteristics: an explosion so powerful that magma was ripped apart, generating colossal amounts of ash. Each eruption was also followed by the collapse of the crust above the emptied magma reservoir, forming a giant caldera—like the 60-kilometer-wide Yellowstone Caldera we see today, which was created during the most recent Lava Creek eruption.

It’s also important to remember that between these enormous events, Yellowstone has experienced many smaller eruptions, often non-explosive lava flows. The last eruption, around 70,000 years ago, was a relatively quiet extrusion of lava.

So, what about the big one? What would we experience as Yellowstone prepares for a volcanic cataclysm, and during the eruption itself?

The Warning Signs

Predicting the exact timeline and warning signs for a super-eruption is challenging. Yellowstone is a restless place, with constant seismic activity, bubbling mud pools, and the ground continually rising and falling. While it seems logical that a super-eruption would be preceded by more intense versions of these same warning signs, research from other supervolcanoes, like Mount Toba in Indonesia, suggests that warning signs could be minimal, offering little notice of an impending, world-changing event.

This is particularly concerning for anyone living within about 100 kilometers (60 miles) of the Yellowstone volcano, as escape might be nearly impossible once the eruption begins. However, recent geological fieldwork indicates that the Lava Creek event was preceded by two smaller, explosive eruptions, perhaps separated by years or even decades. We might see similar “starter” events before the main course. The challenge, from a mitigation standpoint, is that it would be difficult to determine which eruption, if any, is the “super” one until after the fact, once the volume of disgorged material can be quantified. Regardless of the exact volume, any eruption of this magnitude would be cataclysmic for the country.

The Eruption Unfolds

When it comes, the next Yellowstone super-eruption will be impossible to ignore, and its consequences unavoidable, whether you’re nearby or on the other side of the world.

The eruption would likely begin at a single vent where the crust above the magma reservoir is weakest. As gas-rich, highly viscous rhyolite magma, under immense pressure, breaches the surface, it would violently tear itself apart. The initial detonation would be deafening to anyone in the vicinity.

A towering plume of ash and pumice would blast upwards faster than the speed of sound, reaching the edge of space within minutes and then spreading laterally, plunging everything below into darkness. A torrent of hot ash and pumice falling across Yellowstone and the surrounding region would ignite fires, heat the air, and make breathing nearly impossible. But that’s just the beginning.

As parts of the eruption column collapse under their own weight, they would trigger pyroclastic flows—fast-moving surges of hot ash, incandescent gas, and near-molten pumice fragments. These flows would hurtle outwards at speeds exceeding 300 km/h (180 mph), overtopping hills and filling valleys, incinerating and burying everything within about 100 kilometers (60 miles) of the vent.

Meanwhile, the upper part of the ash and pumice column would expand rapidly, forming a gigantic “umbrella” cloud that spreads darkness and a deluge of ash. Within 24 hours, ash would be falling across much of the United States and parts of Canada, causing widespread disruption: power outages, electronic failures, transportation chaos, flattened crops, and contaminated water supplies. Normal life would grind to a halt.

USGS modeling suggests that in most scenarios, ash more than a centimeter deep would cover an area of several million square kilometers. While cities like Miami and New York might only see a few millimeters of ash, Chicago, San Francisco, and Winnipeg could receive up to 3 centimeters. Areas closer to Yellowstone, such as Denver and Salt Lake City (within 1,500 km or 930 miles), would experience extremely disruptive ashfall, potentially meters deep closer to the volcano.

The ash, laden with toxic metals like arsenic, cadmium, lead, and mercury, would pose a long-term contamination threat to water, crops, and animal feed. The eruption would likely unfold in stages, possibly with new vents opening, prolonging its disruptive impact. The most intense phase could occur as the central block of crust above the magma reservoir sinks into the evacuated space, forming a new caldera. In total, the entire event could last for weeks, perhaps even a month. But the immediate aftermath is only part of the story.

A Global Sunshade and Catastrophic Aftermath

While the heavy ashfall would devastate agriculture across North America and cripple the U.S. economy, the truly global impact would come from the vast quantities of sulfur dioxide gas blasted into the stratosphere. Within weeks, this gas would spread across the planet. When combined with atmospheric water vapor, it would form an aerosol of tiny particles, creating a global “veil” that reflects incoming sunlight and significantly lowers surface temperatures.

To put this in perspective, the 1991 eruption of Mount Pinatubo, though a major 20th-century volcanic event, was about one hundred times smaller than Yellowstone’s Lava Creek eruption. Yet, it caused a global temperature drop of about 0.5°C (1°F) for a couple of years. The 1815 eruption of Indonesia’s Tambora volcano, three to four times larger than Pinatubo, had a much greater impact, leading to the infamous “Year Without a Summer” in Europe, with widespread harvest failures and civil unrest.

So, what if Yellowstone, an eruption 25 times larger than Tambora, were to blow? Computer models predict a global temperature drop of up to 4°C (7°F) on average, up to 7°C (13°F) across land, and more than 10°C (18°F) across central North America. While temperatures would slowly climb back within a few years, it could take a couple of decades to return to previous levels. This severe cooling, nearly matching Ice Age temperatures, would be catastrophic for global agriculture, leading to widespread harvest failures and famine on an unimaginable scale, affecting both developed and developing nations. It’s hard to imagine global society and economy surviving in any recognizable form.

A Glimmer of Hope?

There is one small ray of light. A recent NASA study, though breaking with the general consensus, speculates that the temperature fall after a Yellowstone super-eruption might not be significantly greater than that following Pinatubo or Tambora, although the researchers acknowledge significant uncertainties.

Ultimately, the true severity of the resulting cooling won’t be known until Yellowstone erupts again. However cold it gets, the direct impact on the United States would have enormous repercussions worldwide and would severely test the resilience of global society and economy.

Perhaps the only true saving grace, as the latest research tells us, is that it doesn’t look like happening anytime soon.

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Bill McGuire is a volcanologist, climate scientist, writer, and broadcaster. His latest book is Sky Seed.