One of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event. A pyroclastic eruption entails spitti...One of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event. A pyroclastic eruption entails spitting or “fountaining” lava, where the lava will be thrown into the air along with ash, pyroclastic materials, and other volcanic byproducts.