Because of their high temperatures, hot pyroclastic surges may start fires and kill or burn people and animals. Both types of surges can extend as far as 10 km from their source vents and devastate life and property within their paths. During an eruption of Mont Pelee on Martinique in 1902, a cloud of hot ash and gases swept into the town of St. Pierre at an estimated speed of 160 kilometers per hour or more. About 30,000 people died within minutes, most from inhalation of hot ash and gases. Pyroclastic surges have occurred at volcanoes in the Cascade Range in the past and can be expected to occur again.
Pyroclastic surges are turbulent, low-density variants of pyroclastic flows.
Some unusually rapid pyroclastic flows or surges originate from laterally directed explosions from a vent. Because of their high speed and high temperature, pyroclastic flows and surges kill or destroy virtually all that is in their path. Base surges are generated by explosions.