The ash deposits were many inches deep in many cities in Washington. This ash choked humans and animals. People were forced to wear gas masks so they could go outside of their homes. Pyroclasts are particles that are ejected during a volcanic eruption. This is very fine material and was given the name ash because it resembles ashes from the burning of wood or coal.
Volcanic ash is rock that has been exploded and shattered by steam inside the volcano.
Ash and lava flows build stratovolcanoes into mountains with repeated eruptions.