This caldera is Ugashik
, the ring of ridges around the five domes of Peulik volcano, on the Alaska Peninsula. Calderas tend to form after a series of large eruptions. Usually a new volcano starts to grow inside, eventually covering it. This is a typical caldera, less well-formed than the Crater Lake caldera
Caldera-forming eruptions are the largest on Earth. The conditions in the heart of one of these explosions are beyond hellish. Yet geologists are beginning to model them.