What is Pyroclastic Flow?

A pyroclastic flow is a mixture of hot gases and fragments that comes from an erupting volcano. The pyroclastic flow can move very quickly and is the most deadly part of the volcanic eruption. When Vesuvius erupted in 79 AD, burying the town of Pompeii near modern-day Naples, many people were killed instantly when pyroclastic flow came down the mountain. You can find more information here: