Global Volcanism Program | Image GVP-05345
A geologist examines pyroclastic deposits (above hand) from a violent eruption of Half Cone less than 500 years ago. The Half Cone layers overlie dark gray phreatomagmatic deposits from Surprise tuff cone in Aniakchak caldera. The Half Cone eruption produced about 1 km3 of tephra and resulted in truncation of the SE side of the cone.
Photo by Game McGimsey (Alaska Volcano Observatory, U.S. Geological Survey).