Pyroclastic flows and surges can cause substantial damage and loss of life on the slopes of volcanoes that erupt explosively.

The combination of high velocity and density results in large forces being exerted on anything in their path. If the forces are large enough they can cause buildings to collapse and be blown away.

The image here shows an example of the building damage in the city St. Pierre, Martinique, following pyroclastic flows produced during the the devastating 1902 eruption of Mt. Pelée.

In this exercise, you will see the magnitude of forces generated by different types of flows and be able to assess their potential for destruction. The videos below provide some perspective.