Pyroclastic flows (referred to more often today, as pyroclastic density currents) are rapidly moving avalanches of hot rock, dust and gas that flow down the sides of a volcano. What makes them especially devastating is that they are extremely hot and can travel for several miles from a volcano. They can form during an eruption when hot pulverized rock and gas that first rapidly rises into the sky falls back, forming pyroclastic flows that race down the sides of the volcano. Other times, pyroclas