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In-Depth Information
Mountains were thus the result of the tangential stresses of contraction, not
sedimentation.
36
Suess's study of Alpine earthquakes added another wrinkle to this situa-
tion. As he combined his data on the tremor of 1873 with historical records
of the region's past earthquakes, Suess determined that seismic events in
Lower Austria could be mapped along a single line. He concluded that these
movements resulted not from forces of uplift but from “fractures or faults
or some other discontinuity in the earth's crust.”
37
earthquakes in the Alps
propagated perpendicularly to the chain of the mountains and were felt fur-
ther away to the north than to the south. other european mountain chains
showed similar traits. Here was evidence that the Alps arose not simply
through local compression but as the result of thrusting, as the entire eu-
ropean continent moved northward. According to his colleagues, however,
continents did not move; they only rose and fell at a snail's pace. Viewed
over the course of millennia, earthquakes could be but small fluctuations
within this stable cycle. It would take another century for geologists to give
up their belief in the fixity of the continents.
38
In the meantime, Suess ad-
vanced his notion of mobile continents as part of a bid to overcome, in his
words, the “quietism” of the geology of his day, which lavished attention
on “the little polyp building up the coral reef, and the raindrop hollowing
out the stone.” Suess thus accused his colleagues of confining their thinking
to the puny human scale. Against this fondness for what Lyell called “tri-
fling means,” Suess mustered evidence for the formative role of catastrophic
events in the earth's history. Much of this evidence, like the observations he
gathered in 1873, consisted of the accounts of eyewitnesses, often written
for purposes remote from natural science.
39
As a colleague put it in 1913,
“since 1880 the predominant influence of M. Suess has again made the
word 'cataclysm' acceptable in scientific circles.”
40
Suess's investigation of earthquakes in Lower Austria thus provided cru-
cial early support for his tectonic theory, which continued to face resistance
into the twentieth century. It also suggested a research program. In order
to demonstrate that most earthquakes were likewise tectonic in origin, and
to identify their associated faults, it was necessary to multiply such studies.
Geologists would need to correlate the location and direction of as many
earthquakes in as many regions as possible with features of local geology.
Such observations held out the promise of identifying regions of elevated
seismic hazard. Basic geology would go hand in hand with disaster mitiga-
tion. The tectonic hypothesis thus sprang from and supported a reliance on
the earthquake observations of ordinary locals. Would the public comply?
