The eruption ejected about of tephra and collapsed the mountain into a caldera , which now contains the crater lake Heaven Lake . The eruption began with a strong Plinian column , and ended with voluminous pyroclastic flows . An average of of Plinian ashfall and coignimbrite ashfall covered about of the Sea of Japan and northern Japan . This ash layer has been named the " Baegdusan-Tomakomai ash " ( B-Tm ) . It probably occurred in winter in late A.D. 946 . This was one of the largest and most violent eruptions in the last 5000 years along with the Hatepe eruption of Lake Taupo at around 180 AD , the 1257 eruption of Mount Samalas near Mount Rinjani , and the 1815 eruption of Mount Tambora
1815 eruption of Mount Tambora
1815 eruption of Mount Tambora
946 eruption of Paektu Mountain