Abstract
All explosive eruptions produce volcanic ash, fragments of volcanic rock generated when magma or vent material is explosively disintegrated during eruption. Volcanic ash is convected upwards within the eruption column and carried downwind, falling out of suspension and potentially affecting communities across hundreds of square kilometers. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation, and primary production (e.g. agriculture) can lead to significant societal impacts. Even relatively small eruptions such as the Eyjafjallajökull eruption in Iceland in 2010 (Volcanic Explosivity Index of 4) can cause widespread disruption, damage, and economic loss. Knowledge of the likely impacts can support mitigation actions, crisis planning, and emergency management activities. This chapter presents an overview of ash fall impacts for sectors of society including buildings, critical infrastructure, and agriculture; and discuss associated socioeconomic factors. We also discuss the likely response (vulnerability) of these key sectors to ash fall impacts. Broad relationships between volcanic ash thickness and levels of damage and disruption have been outlined. Understanding these vulnerabilities is an essential step towards building resilience for communities.