Based on the history of volcanic activity of Zao stage VI, we examined possible courses of future activity of Zao volcano. All activities will start with precursory phenomena. Next, phreatic eruptions from Okama crater or other place inner part of Umanose caldera will occur, and may cause ballistic materials release, ash fall, pyroclastic surge, and lahar. The possibility of small scales edifice collapse and lava flow swelled out is very low but should be included. When the activity progresses, magmatic eruptions will be taken place from Goshikidake, and cause same phenomena as in the phreatic eruptions but larger in scale. The possibility magmatic eruption takes place without preceding phreatic eruption can not be excluded. Rarely, the activity will go up further and resulted in sub-Plinian eruption. Aside from the above sequence, larger scale phreatic eruption from Goshikidake area should be listed, although the possibility of this is very low.
