Tempo in Geology
Catastrophism, Actualism,
Uniformitarianism
Dramatis Personae
John Playfair
• Companion/amanuensis to James Hutton,
author of Illustrations of the Huttonian Theory of
the Earth (1802).
• Argued vigorously for Hutton’s cycles,
emphasized the importance of finding granite
cross-cutting younger sedimentary formations
and volcanic activity that emerges from well
below ‘primitive’ formations.
• Above all, insists on the vast duration of
geological time.
Robert Jameson
• A Wernerian.
• Also a literalist about the biblical chronology
(though Werner probably was not).
• Founded the Wernerian natural history society in
Edinburgh (a split in the Royal Society of
Edinburgh).
• The Wernerians were focused on the theory; the
London society was more ideologically
empiricist, wanted to ‘gather facts’ independently
of theoretical commitments. (To what extent can
this really be done?)
Catastrophists and Uniformitarians
• Catastrophists explained geological features by
appeal to processes that are no longer going on.
• They also emphasized the scale, power, speed
and violence of these processes
• Uniformitarian explanations appealed to
processes that continue today, and in the strong
form of this position, they also assume that the
average rates of these processes have not
changed.
Some basic distinctions
Same basic Laws
Same
processes
Same rates of
processes
Supernaturalists
No
No
No
Catastrophists
Yes
No
No
Actualists
Yes
Yes
No
Progressivists
(a sub-type of
the actualists)
Yes
Yes
No (changing
steadily—
usually
decreasing)
Uniformitarians
Yes
Yes
Yes
Georges Cuvier
• A great comparative anatomist– the first to clearly establish the fact
of extinction.
• The chief proponent of catastrophism.
• Not only showed that the continent had been repeatedly flooded by
the ocean, but argued also that these floods were ‘convulsive and
lethal’.
• His argument for this drew on the remains of the last incursion of the
sea, in which he included the frozen carcasses of mammoths and
wooly rhinos. But (assuming wrongly that these are tropical
animals) they could only have been preserved in this way if the
freezing temperatures had arrived at the very same time as they
were killed.
• Further evidence included massive heaps of debris, overturned and
faulted strata, and similar dramatic evidence of large-scale
geological processes.
More of Cuvier’s evidence
• The sequence of fossil beds around Paris
shows a series of new faunas, each
replaced by the next, interrupted by
incursions of the sea.
• Cuvier concluded that it was these floods
that exterminated the previous inhabitants,
and that new (related, but different) forms
migrated in to replace them.
Still More
• Foothills of the mountains largely sedimentary rock.
• But these are bent/folded/inclined.
• These rocks underlie the level strata further from the mountains, so
they’re older.
• They also contain different fossils, almost all of extinct species.
• So their bends etc. are evidence of ancient events that both
exterminated these plants and animals, and bent/folded/tilted the
strata.
• Finally, the highest mountains are more disturbed still, and contain
no fossils, indicating a still more violent period during which life was
rare if it existed at all.
• Finally, large blocks of ‘out of place’ rock (erratics); nothing
happening today, Cuvier thought, could have moved these rocks
such great distances.
Present Processes
• Cuvier recognized erosion, landslides,
earthquakes and other processes occurring
today.
• Still, he claimed they just aren’t powerful or
significant enough to account for the geological
record- especially for the elevation of great
mountain ranges.
• Cuvier identified the last revolution with Noah’s
flood, appealing to other flood stories from other
cultures to back up the claim that the oceans
and land had changed place (a Hutton-like
suggestion) within human history.
The age of the earth
• Cuvier, like Werner, is vague about time,
referring only to ‘thousands of ages’
• Even this was far too much for Jameson,
who clung to the Mosaic chronology.
• Ironically, today it’s catastrophism that
attracts biblical literalists, who appeal to
catastrophes (especially the flood) to
‘speed up’ their geology.
Charles Lyell
• Principles of Geology, Vol. 1 (1830) presented Lyell’s
case for uniformitarianism.
• Trained as a lawyer, Lyell preferred geology, and was a
member of the Geological society before he was called
to the bar.
• Lyell took on roles in the society, travelled widely with
other geologists, did field trips all over Europe and began
writing.
• On finding that he could actually make a living as a
writer, he gave up any notion of working as a lawyer.
• Began writing Principles in 1827.
Further
• Lyell conducted field work in Italy and France, including
observations of Etna in Sicily.
• In Principles he argued that present processes proceeding at
present rates could explain the geological record
• The book was controversial and successful, with volumes II and III
appearing in 1831 and 1833. He continued to update it, producing
11 editions and part of a 12th.
The Theory
• Aimed ‘to explain the former changes of the
earth’s surface by reference to causes now in
operation’.
• Granite is an intrusive igneous rock. (Think what
this means about the Alps…)
• From a uniformitarian point of view, the age of
the earth is undeniably immense.
• Sources of bias in geology: We don’t see a lot
of what’s actually going on! If we were
amphibious, we’d do better…cf. also the reversal
of things as seen by the ‘sooty sprites’ of the
underearth…
The importance of time
• How fatal every error as to the quantity of
time must prove… (p. 141)
• The raising of the Andes: Draws on
Darwin’s observations of an earthquake in
Chile; points out how different things
would have to be if we compress the time
required to raise them.
• The case of Etna & its structure. (p. 143)
Etna
• Etna rises up through recent Tertiary strata
(containing fossils that correspond to living
species).
• But it is built (as we can see by looking at valleys
cut into the mountain) of innumerable separate
flows of lava, all comparable in size & form to
flows observed historically.
• Given the historical rate of such eruptions (even
allowing that it might be much higher long ago),
we still get an immense time– all of it more
recent than these very recent sedimentary
strata.
Erratics and fossils
• Lyell proposed erratics
had been carried by
icebergs during a time
when sea level was much
higher and the climate
colder.
• Fossils of terrestrial
animals mixed in with
strata formed beneath the
sea were formed in river
deltas, especially during
floods.
Objections
• Many (and Sedgwick in particular) pointed out that Lyell’s
two principles
– “No causes whatever have from the earliest time to which we
can look back, to the present, ever acted, but those now acting.”
– “(T)hey never acted with different degrees of energy from that
they now exert.”
• seemed unjustified from a theoretical point of view.
• How could he rule out different processes, when the
laws allow for things that don’t happen today? How
could he rule out different rates, when the evidence
suggests that the earth is still cooling from an originally
molten state?
• But the methodological advantages and successful
application of these principles were to Lyell’s credit.
Sedgwick recants his diluvialism
• Our errors were, however, natural, and of the same kind
which lead many excellent observers of a former century
to refer all the secondary formations of geology to the
Noachian deluge. Having been myself a believer, and, to
the best of my power, a propagator of what I now regard
as a philosophic heresy, and having more than once
been quoted for opinions I do not now maintain, I think it
right, as one of my last acts before I quit this Chair, thus
publicly to read my recantation.
We ought, indeed, to have paused before we first
adopted the diluvian theory, and referred all our old
superficial gravel to the action of the Mosaic flood....
(Sedgwick, 1831, pp. 312-314)
Another difficulty for Lyell
• As we’ve already seen, the fossils found in
Paleozoic, Mesozoic and Cenozoic formations
are quite different.
• For example, we find no mammals in Paleozoic
strata, very few (and odd ones) in Mesozoic, and
many & increasingly familiar ones in Cenozoic.
• If the world really hasn’t changed how it works in
all of geological history, this apparent history of
life is awkward to explain. What ‘present causes’
could account for such dramatic changes in
living things?
Tempos
• Tempo giusto: exact/ standard time (no
variations, no slowing or speeding up).
Thus, Uniformitarian.
• Tempo rubato: speeding up or slowing
down (at the discretion of the performer).
Thus allowing for variation in processes, or
at least their rates.