Tephra is a generalized word for the various bits of debris that are launched out of a volcano during an eruption, regardless of their size.[4] Pyroclastic materials are generally categorized according to size: dust measures at <1/8 mm, ash is 1/8–2 mm, cinders are 2–64 mm, and bombs and blocks are both >64 mm.[5] There are different hazards associated with the different kinds of pyroclastic materials.