Calderas are massive crater-like depressions that can cover many tens of square miles. These calderas form when volcanoes explode with terrible destruction, completely obliterating the original volcano, and surrounding area.
One famous example of a caldera is North America’s Crater Lake. Around 7,000 years ago a massive volcanic peak reaching 12,000 feet in elevation set in this location. A powerful eruption blasted the top 4,000 feet away, leaving a deep bowl shaped caldera. Since that time, a new dome has begun to form in the center of the caldera.