Aerial view of the roiling pool in the summit crater of Korovin volcan. Note that the walls immediately adjacent to the pool have been stripped bare (presumably by intermittent, minor phreatic blasts from/through the pool).
McGimsey and others (2008) and Neal and others (2009) detail satellite imagery and field observations of ash on the upper east flank of Korovin volcano in late June - early July, 2004, likely from a small phreatic eruption of Korovin prior to late June.