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Pompei and Herculanum were wiped out by a particular type of volcanic event called a Nuee ardente (pyroclastic flow).
These are utterly violent and fascinating phenomena, videos of such might certainly provide a vivid addition to your presentation and bring across the suddenness and utter violence of what happened in 79.
see:
The 1991 Unzen flow - https://www.youtube.com/watch?v=FyMW9Y5_yww
Some Merapi flows: https://www.youtube.com/watch?v=Bz7WCttwXQk
the 2014 Sinabung flows: https://www.youtube.com/watch?v=-iSFM-T-F_0