Pyroclastic materials include ash, pumice , and tuff . Let's discuss each. Ash is defined more by its size rather than by its composition. Ash is anything that shoots out of a volcano that's two millimeters or smaller in diameter. It's the little stuff.
Pumice is a form of volcanic glass that's filled with holes.
These holes form when gases escape from the lava. Some pumice forms as a hardening crust on a lava flow, and other times pumice is ejected directly from an explosive eruption. And that's tuff, actually. Tuff is a type of igneous rock formed by the consolidation of ash. Now let's talk about volcanic edifices.