Katmai caldera, Katmai National Park and Preserve. The caldera formed on June 6-7, 1912, in response to withdrawal of magma that vented at Novarupta, 10 km west, at the head of the Valley of Ten Thousand Smokes. The caldera walls rise 250-800 m above the lake, which is 250 m deep and still filling.
Image courtesy of AVO/USGS.