2. Yellowstone Caldera, USA
Often called a “supervolcano,” the Yellowstone Caldera has the potential to erupt with devastating global effects. Though its major eruptions are rare, ongoing geothermal activity—including earthquakes and ground swelling—has raised eyebrows. While an eruption may not be imminent, scientists constantly monitor its active magma chamber beneath the park. Even a moderate event could massively impact air travel, climate, and agriculture across North America.