Associate Safety Professional Practice Exam

In the event of a nearby volcanic eruption, what hazard poses a fast-moving threat to a town?

1. Lava flow

2. Volcanic ashfall

3. Pyroclastic flow

4. Toxic gas emissions

The correct answer is: Pyroclastic flow

The correct answer is pyroclastic flow, which is a fast-moving volcanic hazard consisting of a mixture of hot gases, ash, and volcanic rock that flows down the slope of a volcano at high speeds. This flow can travel at speeds exceeding 100 km/h (about 62 mph) and can reach temperatures of around 1000 degrees Celsius (about 1832 degrees Fahrenheit). Due to its speed and high temperature, pyroclastic flow is extremely dangerous, as it can obliterate anything in its path and affect areas that are far from the volcano itself. In contrast, lava flow tends to move more slowly, allowing for some evacuation time. While it is destructive, it does not pose the same immediate and widespread danger as pyroclastic flows. Volcanic ashfall, while it can bury areas and pose health risks, tends to distribute more evenly over a wider area and provides some indication of volcanic activity before it impacts a locality. Toxic gas emissions can be hazardous, but they generally have a more localized effect compared to the extensive and rapid destruction caused by pyroclastic flows. Therefore, the immediate threat during a volcanic eruption is indeed the pyroclastic flow, which is characterized by its speed and potential for widespread devastation.