These two movies show the results of two laboratory experiments of pyroclastic density currents - one unobstructed and one with a low topographic barrier. The flow was a generated using heated talc powder in air in a tank that is 6.5 x 1.8 x 0.6 m in dimension.

Details on the experiment and one more movie with a tall topographic barrier can be found at:

Andrews, B.J. and Manga, M., 2011, Effects of topography on pyroclastic density current runout and formation of coignimbrites: Geology, v. 39, no. 12, p. 1099-1102.