The two units of the debris avalanche are distinguished by their appearance. One features long hummock-like hills, as is typical for volcanic debris avalanches, and the other has ridges which vary in length from . The ridges range from only a few meters to more than in height, and from in height. Such ridges have been observed in other collapse deposits such as at Shiveluch volcano in Russia, and have been explained by sorting processes that take place within granular flows. The differences between the two units appear to be because the first unit was formed from the basal part of Tutupaca, while the second unit was formed by the more recent lava domes of the eastern volcano and formed a granular flow.