The city of Mammoth Lakes sits on the edge of the Long Valley Caldera formed around 700,000 years ago. This caldera is 15 miles in diameter and is North America's second largest. 1. The Long ...

during which the Bishop Tuff extruded and the caldera, 10 miles by 20 miles in size, was created. The supereruption so ravaged the area that the modern city of Los Angeles existed under a ...