If the Yellowstone volcano were to erupt, this could be how the ash spreads
Yellowstone is not only the largest but also the most popular location for megafauna in the contiguous United States. In addition, it was established before any other national park and contains North America’s biggest volcano, the Yellowstone Caldera.
The last time the Yellowstone Caldera erupted was 640,000 years ago. However, volcanic eruptions are notoriously difficult to predict. This map shows how ash would spread in the event of another eruption and covers all of the United States.