Apyroclastic flow, pronounced pie-roh-class-tick, (also known as apyroclastic density current) is a flow of hotvolcanic gas andtephra, during avolcanic eruption. A cloud forms over thecurrent of hotrock. This boiling column of superheated gas,sand, tephra,obsidian, andpumice can reach soaring temperatures of1,000°C (1,800°F) and its average speed ranges from100km/h (30m/s; 60mph) to700km/h (190m/s; 430mph).
They are extremely dangerous and can be deadly. A person cannot outrun a pyroclastic flow. Learn more at USGS.gov.
