not grouped with other, more common events. An example would be a large
meteor strike of theEarth—certainly a potentially “hazardous” occurrence, but
so rare that in general it is not included in studies of natural hazards. Hazards that
have geological origins are often termed “geohazards” to differentiate them from
other types of hazards, although some commentators regard any hazard located
in the biosphere to be a geohazard. The major hazards that are geological in origin
areearthquakes, landslides, volcanic eruptions, and avalanches; and although
other events may occur, they typically arelimitedinscopeandcausedeathand
destruction only on a localscale. Climatological hazards includehurricanes
(called typhoons in the Pacific and Indian Ocean basins), tornados, blizzards, heat
waves, extended periods of drought, and geomagnetic disturbances, which have
extraterrestrial origin, as they are caused by solar activity. The primary hydrolog-
ical hazards are represented by floods, and tsunamis, although other localized
hazards exist.
Enormous destruction may result if a natural hazard causes a natural disaster. In
terms of single disastrous events, earthquakes and floods historically have caused
the greatest loss of life. The most catastrophic loss of human life in history was
the result of extended flooding along the Huang He River in northern China in
1931, which killed an estimated 1 million people. Combined with the results from
other flooding in 1931, the total number of deaths from natural disaster that year in
China approaches 2.5 to 4 million. The greatest loss of life due to an earthquake
also occurred in China. In 1556 a massive tremor struck northern China in a region
where thousands of people lived in cavescarved from the local loess soil. The
earthquake is believed to have killed inexcess of 800,000 people, with most of
the dead buried alive by the collapse of their dwellings. But these examples, while
stunning in the magnitude of loss of life, pale in comparison to the death toll of
infectious diseases, especially virulent outbreaks of maladies with a high mortality
rate. The Black Death, an epidemic of bubonic plague in the 14th century, killed
almost a third of the population of Europe in only two years, or an estimated total
of approximately 100 million people. Just in the 20th century, influenza pandem-
ics, smallpox, malaria, and AIDS have resulted in well over 1 billion deaths.
Famines also account for a large number of fatalities. While earthquakes, volcanic
eruptions, and hurricanes receive a great deal of media attention when they occur,
the most devastating natural hazards clearly are disease and famine.
Natural hazards are a major concern for those in the field of emergency man-
agement and response. Although natural hazards are found everywhere on the
planet, they take a disproportionate toll in the developing world, where a larger
population may be potentially affected by natural hazards, and fewer precautions
are available to limit loss of life. For example, hundreds of thousands of people
in Bangladesh live in the delta and floodplain of the Ganges River, only a few feet238 Natural Hazards