Six-hundred-thousand years ago, the largest volcano in the Western Hemisphere erupted covering much of what is now the Central United States in a thick layer of ash. The cataclysm left behind a massive caldera that today is known as Yellowstone National Park.

After volcanologist Milton Bainbridge is found dead under mysterious circumstances, USGS volcanologist Jason Trask is called in from overseas to replace his former boss and work at Yellowstone Park with Bainbridge’s assistant Carlene Carlson. Trask and Carlson discover records in Bainbridge’s computer that indicate Yellowstone is about to erupt again, only this time the survival of millions of Americans in 13 states is threatened if they cannot be evacuated from the deadly path of the fallout. To make matters worse, a terrorist organization is planning on using the disarray in the aftermath of a Yellowstone eruption to topple the government of the United States. Trask and Carlson face off against a government that doesn't believe an eruption is eminent and a terrorist organization preparing to use that denial to their advantage.

Caldera is filled with technical accuracy in the lives of volcanologists assigned to Yellowstone National Park and the challenges they face when presented with the reality of a national disaster of unimaginable proportions.