Reactivated volcanic activity started between 25,000 and 14,700 years ago and led to the emplacement of ash flows, pumice layers and tephra from phreatomagmatic and explosive eruptions, with deposits having thicknesses ranging from in many places. The total volume of each eruption deposit ranges from and they crop out as far as from Ubinas. It is likely that the summit caldera formed during this time period, before 9,700 years ago.