A natural disaster can be defined as some impact of an extreme natural event on the ecosystem and environment, and on human activities and society. The concept relies on the interaction of a natural agent—the hazard—with human vulnerability to produce a risk that is likely to eventually materialize as a destructive impact.

Lava flow from an eruption of Mount Etna, Sicily, destroys all trees and plants in its path. (©Vittoriano Rastelli/Corbis. Reproduced by permission.)

Understanding Hazards and Disasters

The driving force, or trigger, of disaster is the natural agent. In this context natural disasters are distinguished—earthquakes, floods, hurricanes, landslides, volcanic eruptions, and so on—from technological ones (toxic spills, transportation accidents, explosions in industrial plants, etc.) and social disasters (riots, acts of terrorism, crowd crushes, etc.). Experts on natural disaster tend to confine the definition to extreme geophysical phenomena and not include...