Geoscience Reference
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church. John Wesley viewed the earthquake as God's
punishment for the licentious behavior of believers
in Lisbon, and retribution for the severity of the
Portuguese Inquisition. Immanuel Kant and Jean-
Jacques Rousseau viewed the disaster as a natural
event, and emphasized the need to avoid building in
hazardous places.
The Lisbon earthquake also initiated scientific study
of geological events. In 1760, John Mitchell, Geology
Professor at Cambridge University, documented the
spatial effects of the earthquake on lake levels through-
out Europe. He found that no seiching was reported
closer to the city than 700 km, nor further away than
2500 km. The seiching affected the open coastline of
the North Sea and shorelines in Norwegian fjords,
Scottish lochs, Swiss alpine lakes, and rivers and canals
in western Germany and the Netherlands. He deduced
that there must have been a progressive, wave-like
tilting movement of the Earth outward from the center
of the earthquake, different to the type of wave
produced by a volcanic explosion.
Mitchell's 1760 work on the Lisbon earthquake effec-
tively represents the separation of two completely dif-
ferent philosophies for viewing the physical behavior of
the natural world. Beforehand, the Catastrophists dom-
inated geological methodology. These were the people
who believed that the shape of the Earth's surface, the
stratigraphic breaks appearing in rock columns, and
the large events associated with observable processes
were cataclysmic. Catastrophists believed events had to
be cataclysmic to allow the geological record to fit with
the date for the Earth's creation of 4004 BC, as deter-
mined by Biblical genealogy. Charles Lyell, one of the
fathers of geology, sought to replace this 'catastrophe
theory' with gradualism - the idea that geological and
geomorphic features were the result of cumulative slow
change by natural processes operating at relatively
constant rates. This idea implied that processes shaping
the Earth's surface followed laws of nature as defined by
physicists and mathematicians as far back as Bacon.
William Whewell, in a review of Lyell's work, coined the
term uniformitarianism , and subsequently a protracted
debate broke out about whether or not the slow
processes we observe at present apply to past unobserv-
able events. The phrase 'The present is the key to the
past' also arose at this time and added to the debate.
In fact, the idea of uniformitarianism involves two
concepts. The first implies that geological processes
follow natural laws applicable to science. There are no
'acts of God'. This type of uniformitarianism was
established to counter the arguments raised by the
Catastrophists. The second concept implies constancy
of rates of change or material condition through time.
This concept is nothing more than inductive reasoning.
The type and rate of processes operating today charac-
terize those that have operated over geological time.
For example, waves break upon a beach today in the
same manner that they would have one hundred
million years ago, and prehistoric tsunami behave the
same as modern ones described in our written records.
If one wants to understand the sedimentary deposits of
an ancient tidal estuary, one has to do no more than go
to a modern estuary and study the processes at work.
Included in this concept is the belief that physical land-
scapes such as modern floodplains and coastlines
evolve slowly.
Few geomorphologists or geologists who study earth
surface processes and the evolution of modern land-
scapes would initially object to the above concept of
constancy. However, it does not withstand scrutiny.
For example, there is no modern analogy to the
nappe mountain building processes that formed the
European Alps or to the mass extinctions and sudden
discontinuities that have dominated the geological
record. Additionally, no one who has witnessed a
fault line being upthrusted during an earthquake, or
Mt St Helens wrenching itself apart in a cataclysmic
eruption, would agree that all landscapes develop
slowly. As Thomas Huxley so aptly worded it, gradual-
ists had saddled themselves with the tenet of Natura
non facit saltum - Nature does not make sudden
jumps. J. Harlen Bretz from the University of Chicago
challenged this tenet in the 1920s. Bretz attributed the
formation of the scablands of eastern Washington to
catastrophic floods. For the next forty years, he bore
the ridicule and invectiveness of the geological estab-
lishment for proposing this radical idea. It was not until
the 1960s that Bretz was proved correct when Vic
Baker of the University of Arizona interpreted space
probe images of enormous channels on Mars as
features similar to the Washington scablands. At the
age of 83, Bretz finally received the recognition of his
peers for his seminal work.
Convulsive events are important climatic and geolog-
ical processes, but are they likely to occur today? This is
a major question cropping up throughout this topic.
The climatic and geological processes responsible for
most hazards can be described succinctly. However, do
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