Hypothetical Timeline Details Potential Impacts of a Yellowstone Super-Eruption

Scientists have modeled a worst-case sequence for a possible Yellowstone super-eruption, drawing on research from United Kingdom volcanologists. The timeline begins two months before an eruption with a cluster of shallow earthquakes beneath the 34- to 43-mile-wide caldera, prompting analysts to increase monitoring despite such swarms being common.

One month prior, the earthquake swarm deepens, GPS stations record ground uplift, and satellite data show accelerating deformation, suggesting magma movement. The volcanic alert level is upgraded from “normal” to “advisory,” and officials start reviewing evacuation and communication plans while noting the uncertainty of the signs.

Two weeks before the event, tremors become more frequent, uplift accelerates, and changes in geyser activity and gas emissions are observed. Researchers estimate an 85 %–92 % chance of an eruption within three weeks, leading to a “watch” alert and an orange aviation color code, with aircraft rerouted around the region. An evacuation zone of roughly 62 miles is defined, potentially affecting about 200,000 residents and visitors.

At the onset, a surge of shallow earthquakes and rapid magma heating of the hydrothermal system generate violent explosions that eject steam, mud, ash and rock. Temperatures may reach 650 °C–800 °C, and ash clouds spread hundreds of miles, later carried thousands of miles by high-altitude winds.

In the first day, ashfall disrupts roads, reduces visibility and strains power and communication networks. Agricultural areas across several states could be buried, threatening crops and livestock, while major cities farther away may experience reduced daylight and hazardous air quality.

Within three days, ash accumulation could reach several feet in parts of Montana and inches in cities such as Salt Lake City and Boise. The ash’s electrical conductivity may cause short-circuit failures, and its weight can damage roofs and infrastructure. Water, sewage, heating, fuel and transport systems could be compromised, leading to shortages of essential supplies.

Over the following weeks, continued ashfall hampers transportation, blocks drainage, and forces airport closures due to engine damage risk. Rail and freight networks, as well as farms, face operational challenges, while livestock and crops suffer from burial and contamination.

Months after the eruption, intermittent explosions persist, and wind and precipitation repeatedly redistribute ash. Health services report increased eye, throat and respiratory irritation. Sulfur dioxide released aloft forms sulfate aerosols that reflect sunlight, potentially lowering global average temperatures by up to 3 °C, with regional variations.

A decade later, communities would still be rebuilding infrastructure and adapting agricultural practices to altered climate and soil conditions. Long-term exposure to fine ash particles could elevate respiratory disease rates, prompting ongoing medical research.

Over geological time scales, the eruption’s scar would erode, vegetation would recover and the landscape would change, leaving only geological evidence of the event.