1. Drift Precursors

2. Drift as case study of scientific method (& scientific ‘revolution’) Insights: (1) Science isn’t the ‘truth’, it’s a process for convincing others of the best answer to a question. (Corollary: too much introductory ‘science’ in school is spent memorizing ‘how the world is’ and not seeing that science is a process of rational inquiry) (2) The importance of data/observations in a paper. To convince specialists, papers must contain convincing data. (3) When a concept becomes accepted as a basic theory (‘law’), then the concept only is taught in order to more quickly digest/encapsulate the facts. (theories are taught as ‘truth’, but a duel between theoretical concepts is not what convinces practitioners) (4) Wegener rightly gets lion’s share of credit because he marshalled and digested a great deal of observations to support his insight (5) however, new observations led to the acceptance of drift…

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5. Gondwana Landbridges

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7. Isostasy – Contradicts Oceanic Landbridges Felsic cont. crust (Sial) Basaltic ocean crust (Sima) Continental crust ‘floats’ — can’t just rise and sink 5km at will…

8. But Also Contradicts Geosynclines… (isostasy was not fully accepted until 1960s)

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15. Holmes Europe-NAm Mountain Fit

16. ‘ Flaw’ with Wegener’s drift — no plausible mechanism

17. Criticism: 1928 Drift Conference…

18. Holmes 1928: Modern Mechanism (Convection)

19. Holmes 1928: Modern Mechanism (Convection) 2

20. Holmes 1928: oops

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38. This animation shows progressive stages in the opening of the Atlantic Ocean. The youngest rocks (in red) clearly outline the mid-ocean ridge system, complete with transform faults. The oldest ocean crust (in blue), is confined to offshore regions adjacent to the United States, Canada and western Africa. This distribution demonstrates that the North Atlantic began to open before the South Atlantic.  PC version  Mac version PC version Mac version Sea Floor Spreading

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42. The polarity of Earth's magnetic field reverses with time. The main figure demonstrates how sea-floor anomalies, also known as magnetic stripes, develop during sea-floor spreading. The inset image records the reversal of Earth's dipole.  PC version  Mac version PC version Mac version Magnetic Reversals

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46. 03_Featured_Art.jpg Zoomable Art  PC  Mac PC Mac

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