A supervolcano lies beneath Yellowstone National Park but shouldn’t erupt for thousands of years. If it did erupt, it could have some pretty extreme effects on the surrounding areas. For starters, it would likely cover the ground with as much as 4 inches of gray ash. In addition, the supervolcano would spew sulfur dioxide, a gas that can lead to acid rain. The explosion likely wouldn't wipe out human life, but it certainly would be destructive.