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Building a Theory

Building a Theory. Example Plate Tectonics Text: Chapter 2 with parts of Chapter 1. Steps on Scientific Method. 1 Collection of facts based on observations and measurements 2. Develop possible explanations (hypotheses) ( a stories ) Multiple working hypotheses

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Building a Theory

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  1. Building a Theory Example Plate Tectonics Text: Chapter 2 with parts of Chapter 1

  2. Steps on Scientific Method • 1 Collection of facts based on observations and measurements • 2. Develop possible explanations (hypotheses) (a stories) • Multiple working hypotheses • 3. Test hypotheses with additional facts to get the best explanation (theory) • 4. Accept, reject, modify theory

  3. Paradigm • Theory that is held with a very high degree of confidence and is comprehensive in scope. • Paradigm Shift – The replacement of an existing paradigm with a better paradigm. • Technology provides new information • New facts don’t fit existing paradigm • A major change in understanding • Occurs at decade to century time scale • Tremendous economic opportunity

  4. Observational Facts (1830-1859) • Continents consist of relatively horizontal sedimentary rocks and disturbed belts (mountain ranges). • Many disturbed belts consist of unusually thick sequences of sedimentary rocks that were deposited in shallow water. • Thick sequences of sedimentary rock or ocean trenches occur adjacent to disturbed belts.

  5. Geosynclinal Theory • Paradigm 1859 – 1969 (110 years) • Peaked in 1951 • Based on distribution of rock units, disturbed belts, and mineral resources • Oldest crust is in continental interiors • Challenged 1912 – 1930 • Shape of continents • Paleoclimate data from fossils • Distributation of some fossils

  6. Ideas and Technologies • Radiometric age dating • Paleomganetics (Inclination, Declination) • Tectogene (thermal convection of the mantle) • Seismic Model of the Earth • Post WWII geophysics • Map of the sea floor • Sputnik 1956 • International Geophysics Year 1958 • Project Mohole (1957-1966)

  7. Paleomagnetics • PALEOMAGNETIC TIMESCALE

  8. Seafloor Paleomganetics

  9. Plate Tectonics • Major components of the theory were developed by several independent researchers (1961-1969). • J. Tuzo Wilson (Canadian) • Wilson Cycle

  10. Wilson Cycle • Continent fragmentation • Formation of new ocean floors between continent fragments • Closing of old ocean basin • Continent fragments collide to form a new continent with a new mountain ranges marking the collisions

  11. Wilson Cycle • Successive cycles take longer • Crust becomes thicker • Crust becomes stronger • Progressive decline in radiogentic heat sources • Progressive decline in geothermal heat • Present cycle began about 175 million years ago with the fragmentation of Pangaea (supercontinent)

  12. Present Wilson Cycle 175 my to Present

  13. Previous CycleAssembly of Pangaea 600my to 300 my • ..\..\Desktop\applachian Orogen.jpg

  14. Features – Hot Spots

  15. Features – Hot Spots

  16. Divergent Boundaries

  17. Convergent Boundaries • Ocean – Continent • Ocean – Ocean • Continent - Continent

  18. Transform

  19. Transform

  20. Present Plate Motions

  21. Assignment • Chapter 3 Minerals atomic number atomic weight octet rule

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