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Lecture 2

EESA06H3 Lecture Notes - Lecture 2: Francis Bacon, Bruce C. Heezen, Marie Tharp


Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles
Lecture
2

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Key Steps to Plate Tectonics
North America and Europe can be "fitted together": 1600 (Francis Bacon)
An "ancestral continent": 1858 (Snider Pellegrini)
"Earth's Plan": 1910 (Frank Taylor)
"Continental Drift" and Pangea: 1915: (Alfred Wegener)
Mantle convection currents: 1928 (Arthur Holmes)
Mid-ocean ridges and trenches: 1957 (Marie Tharp and Bruce Heezen)
"Sea floor spreading": 1962 (Harold Hess)
1965 "wander paths" for continents (Ted Irving) and "magnetic stripes" on the
ocean floors (Fred Vine
Computer reconstruction of Pangea: 1965 (Tuzo Wilson)
Plate tectonics 1968 (Tuzo Wilson)
Supercontinent cycle 1974 (John Dewey)
Sir Francis Bacon (1561-1628)
Was a naturalist
1570 -> first world atlas
1610 -> first suggestion that the continents had been together
Did not suggest that they had moved together
Looked at the coastlines of Europe, western Africa
Said that they appear to shift
Suggested that those continents were together
Atlantic ocean had been separated through strong currents
Antonio Snider Pellegrini 1858: An "Ancestral Continent"
Said that continents had once been together
Argued that it was because of erosions
First scientific proposal
Ancestral continents (before and after separation) -> 1858
No implication that the continents had been together and then drifted apart
Lecture 2
Monday, January 13, 2020
1:48 PM

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Carl Schuchert (1858-1942)
Permanentism: continents are fixed in position connected by land bridges which
sink to create oceans
Continents grew in size but did not move
Expanding earth model: result of earth expanding and stretching
Contracting and cooling earth model
Like fruit drying out
Wrinkles and folds, which are in rocks
Rock layers were originally horizontal
Result of contraction, and shrinkage of the Earth
No recognition that the continents have moved
Mobilism
Frank Burley Taylor (1910): "Earth's plan"
Where continents drift as "sheets" that are moved by tidal forces
Recognized that the mountains were the result of continents moving
Talked about earth's plan -> scoffed and ignored it
Too far removed from permanentism
The crust is pushed down under the weight of the ice
Ice melts and the crust recovers
Taylor mapped knew this because he mapped ancient lakes
Surveyed the elevation of the shorelines

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Surveyed the elevation of the shorelines
Should be horizontal
Were tilted up the north
Ice were thicker to the north so load on the crust was greater and amount of
depression was more
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Believed all continents were clustered at the core and separated through Earth's
rotation
People said those forces exist but were too weak to move land masses
Alfred Wegener: 1915
Die Entstehung der Kontinente und Ozeane ("The Origin of Continents and
Oceans")
Pangea ("All the lands)
Died in Greenland 1930
Matching rock types of the same age from one continent to another to reconstruct
Pangea
And it made sense of the fossil record on continents that are now far apart
The response to 'Continental Drift' was extremely negative
And opposed by geophysicists such as Sir Harold Jeffreys (1891-1989)
The Earth's interior was considered to be too stiff to allow continental drift
Arthur Holmes (1928)
Convection currents driving the drift of continents
Largely ignored in North America
Said the continents had fit together -> Pangea (all the lands)
Plotted the geology and fossils of the land which made sense
Professional distrust because he was German and because he was not a geologist
Was a polar explorer
His idea of continental drift died in 1930
Had not explain the mechanism
How could the crust move around something that was hard (mantle)?
Matching rock types of the same age from one continent to another to reconstruct
Pangea
Able to identify distinct belts
Deserts, north pole, tropical trees, etc.
And it made sense of the fossil record on continents that are now far apart
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