A number of lava flows are seen on the flank. They spilled from the steaming summit crater toward the north, because the crater rim is lowest to the north. The topmost and longest lava flow is the Oni Oshidashi, which erupted in 1783. To the west of the two-level crossing, there is a 1 km-wide horseshoe depression, which is open to the north. The Oni Oshidashi invaded the depression from the west, burying half of it. This depression is presumed to be source of the notorious Kambara debris avalanche, which occurred in the morning of August 5th, 1783, and overwhelmed 1,400 persons on the flank and also along the Agatsuma River. Several old pictures depict Yanainuma marsh before the eruption. The dynamic interaction between hot Oni Oshidashi lava and cold water of Yanainuma marsh seems to have been responsible for the Kambara debris avalanche. In the foreground is the Agatsuma ignimbrite, which erupted on the day before: August 4th, 1783. Many cottages are identified on it among the trees.