Merapi volcano, located at Central Java - Indonesia, is one of the most active volcano in the world. Since 1006, about 60 cycle of activity were reported. During the 100 years, more than 24 activities recorded in detail. Dome formation and pyroclastic flow have been occurred in turns.
The major role played by magma mixing processes in the origin of intermediate lavas (andesites of the calco-alkalic series and trachy-andesites of the alkalic series) is demonstrated by four different features : 1. Frequent, 2. Position of the lava mixtures, 3. Role played by the transfer of phenocrysts, 4. Geochemical control