A precise division and stratigraphy of the volcanic products of Mt. Vesuvius's eruption in A. D. 79 are proposed. The volcanic products can be divided into two fundamental categories: the Pompeii Pumice Layer and the Pompeii Surge Formation. The Pompeii Pumice Layer is mainly composed of pumice fall grains and is intercalated with three volcanic ash beds. The Pompeii Surge Formation contains pyroclastic-flow deposits, debris-flow deposits, and air fall ash layers.
The full succession of the pyroclastic-flow deposits consists of a basal lithic part, a middle volcanic sand part, and an upper volcanic ash part, though these are often intermittent.
The most powerful flow is the PD-2 debris-flow which overturned house walls and, its deposit contains big blocks of house material such as pieces of wall, roofing tile, and so on. The PS-3 pyroclastic-flow was also powerful as shown by the human skull and rather large timber material the deposit contains.
It is supposed that the Pompeii Pumice rained down for 30-40 minutes. The paths of the flows are reconstructed as shown in Figure 12.
It is supposed that many buildings and towers were not completely buried by the volcanic products from the Vesuvius eruption, and that some destroyed remains of the artificial materials might have still been visible on the ground surface just after the eruption. A timetable of the volcanic activity of Vesuvius and the accumulation of the volcanic products is proposed.