Pyroclastic material is the mixture of hot rock, ash and lava fragments that are thrown from the vent of a volcano during an eruption. Pyroclastic material typically moves away from the vent at a rapid rate of speed carried along by hot gases.
Pyroclastic material is transported during an eruption in three ways: a pyroclastic flow, a pryoclastic fall or a pyroclastic surge. A pyroclastic flow is when a mixture of gas and volcanic rock move away from a volcano; it stays close to the ground and flows down hill. A pryoclastic surge differs from a pyroclastic flow in that a surge has a higher proportion of gas to rock, making it able to rise over ridges and hills. A pyroclastic fall is when material that has been ejected from the volcano, often high into the atmosphere, falls to the ground.