Geoscience
Research Institute
Origins 12(2):61-63 (1985).
EDITORIAL
It happened suddenly, and the results were devastating. A major
earthquake (Richter 8.1) shook Mexico City on September 19, 1985. The tremor which lasted
about four minutes caused the collapse of over 250 buildings and the deaths of thousands.
Ironically, many died in two large hospitals that had collapsed. Thirty-six hours later, a
second tremor (Richter 7.5) caused further damage of upright and toppled buildings. The
total number of badly damaged or destroyed buildings from the two quakes was estimated at
2500, and the number of deaths was expected to exceed 8000.
Such catastrophes surprise us. If we knew they were coming, we would be
more prepared — or would we? In a way we know that they are coming; seismologists had
warned about potential problems in Mexico City long ago, but Mexico City remained
unprepared. Part of the reason for our surprise is that it is difficult to take the
extraordinary very seriously when the ordinary is so dominant.
Usually life is relatively placid. The normal routine of daily
activities is not exciting. Things do not change all that much. The geologist returning to
his outcrop finds it very much the same as it was the day before. The laboratory scientist
repeating his experiments over and over again to make sure they are valid is not attuned
to the possibility of the unusual. Commonality can almost hypnotize us into thinking only
of the ordinary. Then, once in a while, something unusual like an earthquake jars us out
of our coma and makes us realize that life is not an even continuum, but is definitely
episodic. However, we soon become retrapped into the dull, normal calm, and we are again
unprepared for the shakeup of the unusual.
The dissimilarity between the normal and the unusual illustrates two
contrasting modes of geological thought: uniformitarianism, which proposes that
geologic changes occur by normal processes, and catastrophism, which proposes
changes during unusual catastrophic events, often of worldwide proportions. Recent changes
in geological thought about these concepts have made their definition imprecise;
nevertheless, the general contrast between the two terms remains.
The Scottish geologist James Hutton (1726-1797) was primarily
influential in promoting uniformitarianism (normal processes) to explain geologic changes.
One of his more famous quotations illustrates his emphasis on slow, normal changes over
long periods of time: "What more can we require? Nothing but time." This mode of
thinking is in sharp contrast to catastrophic explanations (unusual events) prevalent at
that time. These explanations often included concepts of a worldwide flood as described in
Genesis. A little later (1830-1833) the English geologist Sir Charles Lyell published his Principles
of Geology which has been called a polemic to destroy catastrophism and "to
sink," as he worded it, "the diluvialists."
For more than a century, uniformitarianism was dogma in geological
interpretation. It is only natural that this should occur, because one usually observes
only slow, normal geologic changes, while catastrophic events are rare. Likewise in
research, the replication which is highly desirable for the establishment of firm
conclusions is much less accessible for the rare event; hence, investigation tends to
concentrate on the readily available, normal data, and the matrix of results is biased in
this direction. This in turn influences our concept of truth towards the normal which can
be further reinforced by our intuition which tells us that the normal is reliable. The
problem of bias due to the unavailability of information is not easily evaluated, and our
concepts of truth are insidiously influenced by this. Hence, concepts such as
uniformitarianism, which favor the normal, easily gain acceptance, even if they
misrepresent the total picture.
Fortunately for geological thinking, the past two decades have
witnessed a retrenchment away from strict uniformitarianism. A modified form of
catastrophism has become acceptable. This is not a return to the classical catastrophism
of events such as the Genesis flood but is a trend in that direction. The billions of
years conceived for the development of the crust of the earth are still preserved by
putting long periods of time between significant catastrophic events. The comments of
several scientists in authoritative publications witness to the present trend.
It is a great philosophical breakthrough for geologists to accept catastrophe as a normal part of Earth history (Erle Kauffman, quoted by Lewin 1983, in Science).
Of late there has been a serious rejuvenation of catastrophism in geological thought (Brown 1974, in Geology).
The profound role of major storms throughout geologic history is becoming increasingly recognized (Nummendal 1982, in Geotimes).
The hurricane, the flood or the tsunami may do more in an hour or a day than the ordinary processes of nature have achieved in a thousand years (Ager 1981, p. 54, in his book on stratigraphy).
The trend towards catastrophism has been generated by evidence found
in the surface of the earth that witnesses to catastrophic activity in the past. It is a
credit to geologists that among the dominant changes in geological thought that have
occurred over the past quarter of a century, the unusual catastrophic event is gaining
significant recognition.
Have we become sufficiently removed from the possibility of being
trapped by the commonality of the normal? Obviously not, or the tragedy of Mexico City
would not haunt us. Because of the plasticity of thought induced by our frail memories and
the ease of noting the normal, the normal will continue to bias our thinking. We tend to
forget the unusual. Unique events such as worldwide floods conceived by classical
catastrophism are even more difficult to envision and incorporate in our framework of
reality, because such events are so remote — in time, magnitude, and complexity
— from the normal that dominates our reference field. While such catastrophes may
leave evidence of their occurrence, it is natural that we should have doubts about such
unusual events; nevertheless, Mexico City reminds us that the exceptional may be very
real. In our search for truth we must not fall into the trap of limiting our concepts to
the normal; if we do, we may suddenly find that we are on shaky ground.
REFERENCES
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