Abstract
Volcanic evolution of the Akakura caldera can be divided into the four stages. (1)Precaldera tumescence stage: regional uplift of basement due to upward movement and accumulation of felsic magma in a large, shallow chamber. (2)Caldera-forming pyroclastic eruption stage: eruption of voluminous pyroclastic flows and piston-cylinder-like subsidence of basement rocks along ring faults. (3)Postcaldera volcanism stage: eruption of andesitic magma via a feeder dykes in a subaqueous setting and quench fragmentation in contact with water to produce the hyaloclastites. (4)Resurgent uplift stage: uplift of central resurgent dome accompanying a significant deformation of the caldera fill with a half-circular reverse fault.
