Pyroclastic flow
A pyroclastic flow, pronounced pie-roh-class-tick, (also known as a pyroclastic density current) is a flow of "lava", as commonly associated with volcanic eruptions. The flows are currents of hot gas, or tephra, during an eruption that sometimes causes rock falls. A cloud forms over the river of hot rock. This boiling column of superheated gas, sand, tephra, obsidian, and pumice can reach soaring temperatures of 1,000ºC and is from 450 to 700 miles per hour.
They are extremely dangerous and can be deadly.
Pyroclastic Flow Media
Pyroclastic rocks from the Bishop tuff; uncompressed with pumice (on left), compressed with fiamme (on right)
Building remnant in Francisco Leon destroyed by pyroclastic surges and flows during eruption of El Chichon volcano in Mexico in 1982. Reinforcement rods in the concrete were bent in the direction of the flow.
A scientist examines pumice blocks at the edge of a pyroclastic flow deposit from Mount St. Helens
The casts of some victims in the so-called "Garden of the Fugitives", Pompeii
