Earth Sciences 240A Lecture 4.

 Uniformitarianism vs. Catastrophism

 

“Is the development of all aspects of Earth the result of slow, predictable processes or is it the result of sudden, chance events…or a mix?”

If Catastrophic:

No value to scientific study of Earth processes

No natural evolution

Only literal interpretation of Bible

Neptunism (preceded Catastrophism)

Championed by: A.G.Werner (mineralogist; charismatic; persuasive speaker)

All rocks (even granite, basalt) precipitated from primeval seas

Conformed to story of biblical floods

Abandoned because could not explain obvious volcanoes

James Hutton (‘father of modern geology’)

Scottish physician; amateur geologist (Remember his unconformity study)

Founded basic work for uniformitarianism (=‘gradualism’); “The present is the key to the past”

Recognized long time essential

1795: published “The Theory of the Earth”

Baron George Cuvier

Brilliant scientist; ‘politically connected’

Champion of catastrophism

All changes: series of sudden, widespread catastrophes

New/old organisms could migrate but never evolve

His diligently recorded case studies contained best evidence for extinctions

Had a tough time explaining skeleton of a mastodon!

Catastrophism Model

Earth initially molten

Six catastrophes made to correlate with 6 days of creation; 7th was flood

Episodic large-scale disruptions during cooling (decreased with time)

Volcanoes were ‘last gasp’ of cooling interior

Dominant from late 18th to mid 19th C

Charles Lyell

Embraced ideas of Hutton

1830: “Principles of Geology”

Promoted unlimited geologic time

Creation vs. Evolution

Lyell: small changes of flora/fauna result of ‘sequential creation’

Charles Darwin (friend of Lyell):

Lyell’s book influenced his observations

H.M.H.S. Beagle

1844: 200-page essay on “Natural Selection”

Lyell agreed he couldn’t explain ‘apparent’ evolution of plants/animals – but no theory of evolution could ever be applied to humans.

Our Modern View

Pro-Uniformitarianism points

Pro-Catastrophism points

            Compromise (sort of!)

Next Lecture: Begin PART B: Space Objects and Impacts