He found eight rock layers near Hiiaka Crater. According to the law of superposition, the bottom layer, called simply the lava flows below the yellow tephra, must be the oldest. The lava flows of 1968-79 are on top and must be the youngest. The cross-section is best interpreted as a series of events that are recorded by layers and features. The oldest layers represent the first event in an area.
Subsequent events add more layers or modify features that are already present.
The events at Hiiaka Crater can be reconstructed as a series of steps. The lava flows below the yellow tephra are not continuous but are truncated by a collapse. The collapse to form a pit crater was the event. The tephra also fell on the breccia in the crater but was not preserved because of the rough irregular surface. The flows cascaded into the ancestral Hiiaka Crater and buried most of the breccia.