Abstract: “When a skyscraper collapses to the ground, the coarsest fragments are rapidly deposited close to the impact zone, whereas the finest counterpart is loaded in a fast and unsteady turbulent flow. Similarly in nature, collapses of volcanic columns, and entire sectors of explosive volcanoes generate thick deposits of coarse material at impact with the ground, instead the fine material is suspended from there on over the landscape to be re-deposited far away in thin deposits. The videos of the spectacular controlled demolitions of hotels and casinos performed at Las Vegas (Nevada, USA) in the recent past definitely reveal the collapse fluid physics of fragmented material. The fragmentation, which is necessary for such a collapse, can make a solid or granular column to powder particles of the size of natural clay or volcanic ash. These particles are mainly transported in suspension by the turbulent flow that is triggered after collapse. The phenomenon of fragmentation is characteristic of ar”

Keywords: collapses, volcanic columns, nature, sectors, explosive volcanoes