Geology Reference
In-Depth Information
FIGURE II.1B
Map showing global distribution of volcanoes,
(modified from
Oilier,
1999)
Geologic setting is important.
The more we can learn
about the geologic locations, conditions, and envir-
onments of past or current geologic events, the better
prepared we can be for future occurrences. For
instance, many landslides take place at sites of
previous landslides. The tragic debris flow that wiped
out Armero, Columbia in 1985 provides a useful
lesson for people living near volcanoes throughout
the world.
Geology is three-dimensional.
Normally humans just
look at the surface of the earth, but in order to
understand what happens at the surface of the earth,
we must also appreciate what is happening below the
surface.
Time is very important in geology.
Geologists take a long-
term view of events. Even though most of the time an
earthquake may not be occurring at a particular site, if
one has occurred in the past, it is reasonable to expect
one again in the future. So too, even though a flood
along a particular river may not be every year, unusual
events occur and people who are not prepared suffer.
Geologic events may have a frequency (how often they
occur; how many years between occurrences).
Different geologic events have different magnitudes.
Some
events, like floods, may impact only one area along a
river. Even the disastrous floods along the Mississippi
River in the US in 1993 did not have a major impact in
many towns, once the water flowed downstream and
the river channel was large enough to hold the
discharge. Other events, like a major volcanic eruption,
may have global impacts on climate. Even small
events, such as a landslide, may have disastrous
impacts on individuals, however.
Rare geologic events can cause great changes.
Although
coasts are dynamic and regularly changing, storms
provide dramatic punctuation to the daily equilibrium
and in a day or so can bring changes that exceed many
years of normal processes. Volcanoes, dormant for
long periods of time, may have new eruptions that
greatly change the landscape.
Geology is different from other sciences.
Geologists focus
on interpreting the historical record of the earth. Envir-
onmental geologists seek to apply our understanding
of this record to the needs of human societies by
integrating knowledge from many disciplines. It is not
always possible for geologists to go to a lab and
determine the answer to questions. Geologic questions
Different geologic processes have different rates.
Some
events, like snow avalanches or earthquakes, may be
over in just a few seconds. Other processes, like floods,
may take days or weeks. See Figure 1.4.
