Geoscience Reference
In-Depth Information
ability. This chapter covers the basic processes of air
movement across the surface of the globe, the concept
of mobile polar highs, air-ocean temperature inter-
actions resulting in the Southern, North Atlantic and
North Pacific oscillations, and the effect of astronomical
cycles (such as sunspots and the 18.6-year lunar tide) on
the timing of climate hazard events.
A description of large-scale storms is then covered
in Chapter 3. This chapter discusses the formation of
large-scale tropical vortices known as tropical cyclones.
Tropical cyclones are the second most important
hazard, generating the greatest range of associated
hazard phenomena. Familiar cyclone disaster events
are described together with their development, magni-
tude and frequency, geological significance, and
impact. The response to cyclone warnings in Australia
is then compared to that in the United States and
Bangladesh. Extra-tropical cyclones are subsequently
described with reference to major storms in the
northern hemisphere. These storms encompass rain,
snow, and freezing rain as major hazards. Storm surges
produced by the above phenomena are then described.
Here, the concepts of probability of occurrence and
exceedence are introduced. The chapter concludes
with a description of dust storms as a significant factor
in long-term land degradation.
Chapter 4 summarizes smaller hazards generated
by wind. Attention is given to the description of thun-
derstorms and their associated hazards. These include
tornadoes, described in detail together with some of
the more significant events. The chapter concludes
with a description of the measures used to avert
tornado disasters in the United States.
These chapters set the scene for two chapters dealing
with longer lasting climatic disasters, namely drought
and floods. Chapter 5 deals with impact of human
activity in exacerbating drought and people's subsequent
responses to this calamitous hazard. Emphasis is placed
on pre- and post-colonial influences in the Sahel region
of Africa, followed by a discussion of modern impacts for
countries representative of a range of technological
development. The second half of the chapter deals with
human response by a variety of societies, from those
who expect drought as a natural part of life, to those who
are surprised by its occurrence and make little effort to
minimize its impact. These responses cover Third World
African countries as well as developed westernized
countries such as the United States, England, and
Australia. The chapter concludes by describing the way
While this topic has been written assuming little prior
knowledge in Earth science at the university level,
there are occasions where basic terminology (jargon)
has had to be used in explanations. More explicit
definitions of some of these terms can be found in the
glossary at the end of the topic. You may have noticed
already that some words in this topic have been
italicized. These terms are defined or explained further
in the glossary. Note that topic titles, names of ships
and botanical names are also italicized, but they do not
appear in the glossary.
Individual chapters are arranged around a specific
concept or type of hazard. The mechanisms controlling
and predicting this particular hazard's occurrence are
outlined and some of the more disastrous occurrences
worldwide are summarized. Where appropriate, some
of humankind's responses to, or attempts at mitigating,
the hazard are outlined.
The hazards covered in this topic are summarized in
Table 1.4, with a chapter reference for each hazard
shown in the last column. The hazards, assessed
subjectively, are listed in the order that reflects the
emphasis given to each in the text. Table 1.4 also grades
the hazards, on a scale of 1 to 5, as to degree of severity,
time span of the event, spatial extent, total death toll,
economic consequences, social disruption, long-term
impact, lack of prior warning or suddenness of onset,
and number of associated hazards. The overall socio-
economic-physiological impact of the hazard is ranked
using these criteria. The most important global hazard
is drought, followed by tropical cyclones, regional
floods, and earthquakes. Three of these four top
hazards rank highest for cost (Table 1.2) and human
impact (Table 1.3). These latter two tables do not
evaluate drought because it develops so slowly and
insidiously that it is often ignored when event statistics
are collected. Of the top ten hazards, six are climatically
induced. Table 1.4 has been constructed for world
hazards. The ranking differs for individual countries
and latitudes. For example, the ranking of hazards in
the United States in terms of economic loss is tropical
storms, floods, severe thunderstorms, tornadoes, extra-
tropical storms, hail, and wind.
The hazards in the topic are organized under two
main parts: climatic hazards and geological hazards.
Climatic hazards are introduced in Chapter 2, which
outlines the mechanisms responsible for climatic vari-
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