Pyroclastic flows are hot, dry flows of volcanic rock debris. The reasons behind the mobility of pyroclastic flow can be attributed to several elements such as the explosive force of the eruption, gas-emitting particles, trapped and heated air within the mass, or a combination of these. Pumice fragments, thick rock pieces, or combinations of the two could make up the next deposits. Pyroclastic flows can vary in size from less mobile avalanches of lithic blocks and ash to gas-rich, highly mobile flows of pumice. The rapid eruption of massive amounts of pumice is the usual source of pumiceous pyroclastic flows, pyroclastic flows primarily composed of lithic material are typically caused by the partial collapse of a volcanic dome or spine or by the sliding of hot rock debris accumulations down the side of the volcano (Hyde, 1975).