Looking into Aniakchak Caldera across the dark tephra cone produced during the May - June 1931 eruption, one of the largest eruptions in Alaska in the last 100 years. In the bottom of the cone is a moss-dappled lava and spatter field produced during the last stages of eruption. Read more about this dramatic eruption, colorfully documented by Father Bernard Hubbard, here http://www.avo.alaska.edu/volcanoes/activity.php?volcname=Aniakchak&eruptionid=293&page=basic In the distance is the exposed wall of Half Cone, (another site of explosive activity) and the turquoise Surprise Lake.
Credit: Image courtesy of AVO/USGS.