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Lecture

ESS102H1 Lecture Notes - Plutonism, Neptunism, Basalt


Department
Earth Sciences
Course Code
ESS102H1
Professor
C.Banks

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Catastrophism and Uniformitarianism
GLG 105 ± lecture 4
Questions on last class:
- How did Werner explain the formation of rocks?
- Rocks originated by sedimenting or precipitation out of a primeval ocean.
One ocean was the origin: rocks formed early in history.
- What evidence substantiated the plutonists' view?
heat pushed the rocks up ± layers of rocks
this would not form from the water it must have formed from a melt, and to have a melt you have
to heat up the rock
widespread granites, sediment layers were pushed up from something from below
Æ
heat
sedimentary rocks, disseminated by heat
compare with lasagne heat has something to do with getting the lose elements together to from a
rock
more on Neptunists versus Plutonists
Werner was initially optimistic that the same sequence of rock types would be observed
everywhere on Earth, proving that a single sequence of depositional events at the very start of
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the basalt controversy"
is basalt sedimentary or volcanic? Werner's originally explained basalt as sedimentary
How did he get it so wrong?
Basalt
- is very fine grained (interlocking cannot be observed)
- forms spectacular cooling cracks
(similar to mudcracks)
has runny lava which forms thin sheets flows can look like sedimentary layers
E.G Iceland
Werner was familiar with the "Scheibenberg" (mountain of slices) near Freiberg.
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mountains),
And
(2) that which has been later altered by heating (unit 4: volcanic rocks) The heat source of the
volcanism in his theory was generated by buried beds of coal on fire.
Necessitated tricky explanations, because basalt is basalt...
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Two of Werner's students (d'Aubuisson and von Buch) found evidence for the volcanic origin of
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deposited on granite of great thickness. Where was the required coal? Certainly not below the
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basalt is volcanic, not sedimentary. Two of Werner's students (d'Aubuisson and von Buch)
found evidence for the volcanic origin of basalts near obvious volcanos.
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thickness. Where was the required coal? Certainly not below the granite, since granite is a
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not sedimentary.
precursors to Hutton and Werner
Gottfried Leibniz (1646-1716) german philosopher invoked both fire and water as geological
agents
Giovanni Arduino (1714-1795) italian inspector of mines in 1760 publication classified rocks into
4 sequences:
Quarternary recent lava and tuff
Tertiary younger limestones
Secondary fossiliferous limestones
Primary cores of mountains
Greek philosophy: fire ± air ± water ± earth are the 4
elements of the universe flood stories in mosaic religions
brief review of neptunists/plutonists controversy
both sides contributed something useful, because both sides had looked at part of the evidence.
both sides were wrong in insisting their theories explained everything.
both Werner and Hutton published very little (Werner: 28 crucial pages in 1787; Hutton: friends
had to push him to publish the crucial paper in 1788).
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way that later writers like Lyell have suggested.
both Werner and Hutton speculated without enough evidence to be sure
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even of Europe; and, what was still more deplorable, when the ingenuity of his scholars had
tortured the phenomena of distant countries, and even of another hemisphere, into conformity
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unkind words by Charles Lyell in 1830
Hutton got it right on the basis of his imagination:
"I just saw it, and no more, at Petershead and
Aberdeen, but that was all the granite I had ever seen
when I wrote my Theory of the Earth [1788 version]."
only later (1794) Hutton observed at Needle's Eye
"the granite introduced, for some length, in small veins
between the stratified bodies"
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