Explosive Materials. The greater the explosivity, the greater the amount of fragmentation Lava & rock material sent into the air is called Tephra : ( Greek, for ash) is a generic term for any airborne pyroclastic accumulation
Pyroclastic flows: (fire fragments) Individual eruptive fragments are called
LAPILLI-- Pea- to walnut-size (2 to 64 mm). They often look like cinders
ASH -- Very fine-grained fragments (< 2 mm), generally dominated by broken glass shards
unusual spaces in the ash layer that, when filled with plaster,
were casts of people that had been caught by the volcanic debris flow and could not escape.