SINNOTT MEMORIAL OVERLOOK WIZARD ISLAND. - Image Courtesy of National Park Service. About 6,850 years ago Mount Mazama, a stratovolcano, collapsed to produce Crater Lake, one of the world's best known calderas. The caldera is about 6 miles (10 km) wide. The catastrophic pyroclasticeruption released about 12 cubic miles (50 cubic km) of magma to the surface. It was one of the largest eruptions in the last 10,000 years.