In the event of a disaster, whether natural or occasioned by man, the day-to-day patterns of life are suddenly disrupted and people are plunged into helplessness and suffering, usually aggravated by a loss of protection, shelter, clothing, food, and medical care. A disaster disturbs the vital functioning of a society. It affects the system of biological survival (subsistence, shelter, health, reproduction), the system of order (division of labour, authority patterns, cultural norms, social roles), the system of meaning (values, shared definitions or reality, communication mechanism), and the motivation of the actors within all of these systems.
A disaster may result from natural phenomena such as: earthquakes; volcanic eruptions; storm surges; cyclones; tropical storms; floods; avalanches; landslides; forest fires; massive insect infestations; and drought. Equally, the activities of man may result in a disaster: armed conflict; industrial accidents; radiation accidents; factory fires; explosions or escape of toxic gases or chemical substances; pollution; mining or other structural collapses; transport accidents; and dam failures. The outbreak of infectious diseases may occur spontaneously or as a result of a disaster situation.
With an ever-increasing population, combined with more industrialization and urbanization, the likelihood of disasters occurring appears to be on the increase. There is a pressing need for studying the causes and effects of disasters, their non-parochial nature, and the staggering impact they have, especially on developing nations.
Disasters produce many therapeutic effects on social systems. The sharing of a common threat to survival and the widespread suffering produced by disaster usually result in a dramatic increase in social solidarity and a temporary breakdown of social and economic distinctions. This resolves pre-existing trauma, and loss or privation motivates people to devote their energies to constructive purposes. It may also provide an opportunity for new innovative solutions to chronic problems of underdevelopment.