Experimental alterations of pyroclastic flow deposits widely distributed in Kagoshima Prefecture were performed at 150oC, 180oC, 200oC, and 300oC. Smectite was easily formed under the presences of NaOH and MgCO3, and FeSO4 and Na2CO3, respectively. By adding a small amount of potassium ion, interstratified minerals were formed.
