A detailed scenario outlining the potential consequences of a Yellowstone supervolcano eruption was published in late September 2026 by Ilan Kelman of University College London and Matthew Blackett of Coventry University on The Conversation. The analysis describes an hour-by-hour unfolding of a super-eruption in the American park, based on scientific models and comparisons, as no human has ever witnessed an event of this magnitude. Although the Yellowstone supervolcano has only a minimal chance of exploding in the short term, its worst-case scenario involves both regional catastrophe and a global cooling effect known as a volcanic winter. The supervolcano’s awakening would begin with weeks of earthquakes and ground swelling above the caldera, with early signs indicating a rise in the probability of an eruption from 21 to 27% a month before the climax, and then from 85 to 92% a fortnight earlier. Scientists would still be unable to determine the exact date of the eruption despite these signals. Authorities would evacuate an area 100 kilometers around the park, affecting about 200,000 people, including residents and visitors. Thanks to this early warning, the direct human toll would remain relatively low, with around a thousand deaths, far less than the catastrophic scenes often shown in disaster films. Beyond this immediate area, the impact would depend heavily on prevailing winds, which would determine which regions are most affected. At the moment of the explosion, an ash column would rise between 30 and 50 kilometers into the atmosphere, well above the altitude where commercial airplanes fly. Hot flows of gas and rock, known as pyroclastic density currents, would descend for dozens of kilometers, destroying everything in their path. At this altitude, the finest particles would remain suspended in the stratosphere for years. Further away, volcanic ash would fall as a thick gray blanket. In Billings, Montana, the ash layer could exceed one meter in depth, up to 1.8 meters according to a model. This would be enough to collapse roofs, short-circuit electrical networks, and disrupt ground routes and airports across much of the United States. Water supplies would also quickly become undrinkable due to contamination. On a global scale, the particles propelled into the upper atmosphere would block sunlight and lower the average global temperature by about 1.5°C. This volcanic winter would last several years and disrupt agricultural seasons well beyond North America. In regions at our latitude, summers would become shorter, and frosts could damage parts of the harvests. The resulting food shortages, famines, and related tensions could lead to a decrease in the world population from 8.3 to 7.9 billion inhabitants within a decade, or between 0.7 to 1.3 billion premature deaths, according to the authors. Humanity has not experienced such a shock since the eruption of Toba in Indonesia 74,000 years ago. However, a super-eruption of this class occurs only after tens of thousands of years of dormancy, and no current signs suggest such an awakening is imminent.