This is the view of the active Brothers Volcano looking from the south into the crater at the summit of the volcano. The site has recently erupted and has ongoing hydrothermal venting. The caldera has two volcanic cones, the smooth one in the left foreground rises about 350 metres above the caldera floor to a depth of about 1,100 metres below sea surface. The smaller cone to the right, which is probably older but still has an intense hydrothermal system at its summit.
The eruption that created Brothers volcano was intense and explosive, creating steep walls whose slopes average 45 degrees. That average doesn't mean straight down, there's a steep drop followed by a modest drop followed by a sheer drop. At the top, the steep walls caved in to form a caldera, or crater, as wide as Mount St. Helens'. The insides of the caldera walls are rugged, with ampitheatre-sized slumps of old rock sliding into the crater.
The images were gathered by the research vessel Sonne during the New Zealand American Submarine Ring of Fire 2007 expedition.