 Complete the following phrase:  The eruption ejected about of tephra and collapsed the mountain into a caldera, which now contains the crater lake named 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 