Almost nine minutes of video of Etna volcano erupting this week in Italy, including a pyroclastic flow. [more inside]
An erupting stratovolcano poses numerous hazards for nearby habitation, but none nearly so terrifying and deadly as the pyroclastic flow. Pyroclastic flows, comprised of tons of superheated sulfuric gases, particulate rock materials and ash, can reach temperatures of 1,830 °F and travel at alarming speeds up to 450mph. Convection of materials within the clouds causes them to become a suspension, fluidizing and thundering noxiously across the surrounding landscape for miles, in some cases even uphill or across open water. Wherever these clouds come in contact with humans the result is catastrophe, as the residents of Herculaneum and St. Pierre, Martinique learned within minutes of the eruptions of Vesuvius in 79AD and Pelee in 1902-- both towns were overwhelmed by pyroclastic clouds, igniting all flammable materials and incinerating and suffocating the inhabitants. None survived Herculaneum, while just two of St. Pierre's 26,000 survived, one of whom was a prisoner condemned to death and awaiting his execution in a dungeon cell. Despite their incredible capacity for violence, pyroclastic flows are also capable of producing mesmerizing, awe-inspiring beauty.