free encyclopedia Mount Asama erupted in 1783 ( Tenmei  3 ), causing widespread damage. [10]  The 3-month-long  plinian  eruption in 1783 produced  andesitic  pumice falls, pyroclastic  flows, lava flows, and enlarged the cone. The climactic eruption lasted for 15 hours; and there was pumice fall and pyroclastic flows. [6]  The complex