Falling ash can turn daylight into complete darkness. Accompanied by rain and lightning, the gritty ash can lead to power outages, prevent communications, and disorientate people.
Ashfalls vary widely in intensity, size of the ash particles, and the degree to which light from the sun is obscured or blocked completely. Because of the unexpected darkness during daylight hours, loud thunder and lightning, and the sometimes strong smell of sulfur during an ashfall, many people describe the experience as eerie and frightening, disorienting and confusing, or dreadful. In extreme ashfall, for example when ash thickness is more than 5-10 cm (2-4 in), people may feel stunned and fearful of the conditions, and may have difficulty breathing if a well-sealed shelter is not available. These thicknesses usually only occur within tens of kilometers of the vent. If caught outside during low visibility, people may become lost or extremely disoriented. If heavy ashfall continues for 12-60 hours or more (a very rare occurrence), roofs may collapse under the weight of the ash, resulting in more confusion, injuries, and even death.
Knowing what to expect during and after an ashfall can help people (1) reduce their anxiety and uncertainty when ash is falling to the ground; and (2) prepare their families and communities to deal with the ash effectively.
Click on the links above (approaching ash clouds, during ash fall, etc.) to learn more about ash clouds and ashfall to give a perspective on what it is like during ash-producing eruptions of different scales.