Volcanic ash consists of tiny jagged pieces of rock and glass. Ash is hard, abrasive, mildly corrosive, conducts electricity when wet, and does not dissolve in water. Ash is spread over broad areas by wind.
Volcanic gases include gases and aerosols emitted from a volcanic vent before, during or after a volcanic eruption.
Subsections listed to the left of this page include more detailed descriptions of volcanic ash, how it is dispersed and deposited, and what ash deposits look like. Also listed is a section describing which gases and aerosols are emitted from volcanoes and how they might interact with ash to form corrosive deposits.