Same process as pyroclastic flow but of much lower density.
A low-density, turbulent flow of fine-grained volcanic rock debris and hot gas. Pyroclastic surges differ from pyroclastic flows in that they are less dense and tend to travel as a low, ground-hugging, but highly mobile cloud that an surmount topographic barriers. Surges often affect areas beyond the limits of pyroclastic flows.
A turbulent cloud of gas and fine rock particles that flows over and above the ground surface at extremely high velocities. More dilute than pyroclastic flows, surges are not topographically constrained but sweep over ridges, hills, and other topographic obstacles.