Caldera, 2.5 km in diameter, formed at crest of Mount Pinatubo on June 15, 1991. A continuous column of ash vented from the caldera floor during late June and July. Initially it filled the caldera, obscuring the caldera interior from view, but, by the time of this photograph, diminishing ash production permitted a view into the caldera. View is southwestward. (Photograph courtesy of J. Mori, June 26, 1991.)