Volcanic ash consists of fragments of pulverized rock,
minerals and
volcanic glass, created during
volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter.
[1] The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as
tephra), including particles larger than 2mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in
magma expand and escape violently into the atmosphere. The force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during
phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometers away.
The ash is just super heated rocks that get pulverized. It is volcanic rock dust.