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Understanding Plate Tectonics: The Dynamic Earth and Continental Drift

Plate tectonics is a relatively new theory, introduced about 30 years ago, that unifies various branches of Earth sciences. The concept builds on earlier ideas, including Alfred Wegener's Theory of Continental Drift from 1915, which lacked a mechanism. Key elements include mid-ocean ridges, seafloor spreading, and paleomagnetism. The theory categorizes boundaries into divergent, convergent, and transform types, illustrating the complex interactions leading to continental movements and the formation of supercontinents like Pangaea and Rodinia throughout Earth's history.

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Understanding Plate Tectonics: The Dynamic Earth and Continental Drift

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  1. Plate Tectonics • Relatively new theory - introduced about 30 years ago • Unifies several branches of the Earth Sciences • http://pubs.usgs.gov/publications/text/dynamic.html

  2. In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated.

  3. Alfred Lothar Wegener • Developed the Theory of Continental Drift • Published “Die Entstehung der Kontinente und Ozeane” in 1915

  4. BUT - • NO MECHANISM !!!

  5. Mid-Ocean Ridges

  6. Seafloor Spreading

  7. Paleomagnetism

  8. Magnetic Striping

  9. Continental Drift +Seafloor Spreading +A few refinements = PLATE TECTONICS

  10. All Plates are surrounded bya combination of three differenttypes of boundaries • Divergent • Convergent • Transform

  11. Divergent Boundary

  12. Mid-Ocean Ridges

  13. Continental Rift Systems

  14. Convergent Boundary • Three Types • Ocean-Ocean Collision • Continent-Ocean Collision • Continent-Continent Collision

  15. Ocean-Ocean Collision

  16. Ocean-Continent Collision

  17. Continent-Continent Collision

  18. Transform Boundry

  19. Satellite measurements of plate movement

  20. Formation and Differentiation of the Earth

  21. Hadean and Archean Eons

  22. Archean (until 2.5 BYA) • Atmosphere composed of methane, ammonia, hydrogen and very little oxygen • Very primitive life – bacteria and stromatolites (3.4 –3.5 billion years ago) - prokaryotes • Cratons of significant size begin to form approximately 3 billion years ago

  23. Prokaryotes • individuals (not colonial) • single celled • no nucleus • no partitions • Originally heterotrophic (ate others)

  24. Autotrophs (organisms capable of creating their own food i.e. photosynthesis) appeared about 2 bya. • Originally referred to as blue-green algae they are actually closer to bacteria and are photosynthetic prokaryotes

  25. stromatolites

  26. Proterozoic • EON • Moderate levels of • oxygen in the atmosphere • were reached about • 2 billion years ago • Oldest multicellular life • ~1.3 bya • Stable continents form

  27. Eukaryotic Organisms • evolved ~1.7 bya • have nucleus and internal chambers called organelles w/ specific functions • unicellular, colonial or multicellular • Introduction of Sexual Reproduction ! • Multicellular “animal” life evolved ~670 Mya

  28. Pangaea I ?? Rodinia was a supercontinent formed about 1100 million years ago (that's 1,100,000,000 years) situated about the South Pole. 750 million years ago, Rodinia broke into three pieces that drifted apart as a new ocean formed between the pieces.

  29. The landmasses would collide again 650 Ma to form Pannotia which would remain a supercontinent until the very end of the Precambrian when it started to break apart.

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