An earlier explosive eruption about 55,900 ± 2,300 years ago may be the origin of the Mohos crater, with another proposed potassium-argon date being c. 220,000 years ago. Mohos crater is probably older than the St. Ana crater. A phreatomagmatic deposit northeast of Mohos was formed by an eruption of the Mohos crater; this eruption may be the source of the Turia type phreatomagmatic deposits, which is dated to have occurred about 51,000 ± 4,800 years ago. In one view, a volcanically quiet period followed an effusive eruption 42,900 years ago named Piscul Pietros and lasted until 31,510 years ago, when a Plinian eruption occurred. This latter eruption deposited thick ash as far as from the vent at one site. Alternatively, 38,900 ± 1,700 years ago a subplinian eruption occurred at Ciomadul; it may have formed the St. Ana crater. This date would correspond to that of the so-called MK-202 tephra. Piscul Pietros has been also dated to be 60,000 ± 5,000 years old and that would imply that the Mohos eruption is older than this.