due to gravity force and forms a PDC. PDCs are
made from tephra (ash, pumice, scoria, rocks, lava) and hot gases. The tephra
and the gases
mix together creating a very mobile mass which can flow over the
surface of the ground similarly to water. The PDCs can be extremely hot and
move at very high speed. The temperature is caused by the fact that the tephra,
rocks, and gases, have only lost
/volcanoes/volcanic-hazards/pyroclastic-flow/