Volcanic ash is pulverized rock ejected from a volcano. Unlike wood ash, newly ejected volcanic ash is sharp and abrasive. It can damage car finishes and scratch eyes. It can clog machinery, vents, and pipes, and can cause respiratory discomfort. In large enough quantities, its weight can be enough to collapse roofs, especially if it gets wet.
Below are some sources of information on the nature of volcanic ash and how to prepare for and recover from a volcanic ashfall.
How do I find out which way the ash is traveling?
What effects can volcanic ash have, and how can I prepare for or recover from an ashfall?
What are some other resources about volcanic ash?