Burning Clouds

Pyroclastic flows are also called nuees ardentes - or "burning clouds" - and are probably the single most destructive weapon in nature's armoury, capable of flattening cities in seconds.
It was such a catastrophe that destroyed the Roman town of Pompeii in AD79.
The 3,300 ft Chaiten Volcano, 800 miles south of the Chilean capital Santiago, is erupting for the first time in thousands of years, sending a plume of ash into the sky that stretches as far as Argentina.
It is also spewing out chunks of lava and hot rock. Authorities have already evacuated around 4,200 people from the town of Chaiten, six miles from the volcano, but 300 civilians and troops remain and are being evacuated now. Rescue is complicated by the fact that southern Chile is fragmented by fjords and access is often difficult.