2. Continental Drift Lyell proposed movement of continents to account for climate change evident in fossil record BUT did not change shape or position relative to each other

3. Continental Drift Tyler proposed crustal changes to account for mountains and island chains

4. Continental Drift Tyler proposed crustal changes to account for mountains and island chains

5. Continental Drift Wegener Observations Alignment of mountains and rock strata matched on opposite sides of Atlantic Glacial deposits displaced towards North Pole Coal belt of N. Amer. and Europe suggested tropics

6. Continental Drift Wegener’s conclusions Continental rock, sial (silicon and Al) lighter than ocean floor (basalt), continents float on fluid mantle Once a supercontinent, Pangaea, that broke into smaller plates Breakup began as rift valley and widened into ocean

7. Continental Drift Continental blocks (plates) retained their shape except where mountain building (can still join the plates now separated) Movement of plates different Radioactive heating from mantle causes plate movement

8. Late Supporting Evidence Computer mapping fit continental shelf of continents together Discovery of submarine volcanoes (guyouts) Ocean floor is basalt and younger than continental rock (max. 150 mya vs. > 1 billion for continental rock) Midoceanic ridge, continuous 65,000 km system on seafloor Magnetic anomalies from differential deposition of magnetized rock

11. Tracking Continental Movement – Remnant Magnetism

12. Major Tectonic Plates

13. Age of islands relative To distance from rift zone

15. Drift and Life 600 – 650 mya first multicellular life 475 – 525 mya Cambrian explosion 400 – 450 mya first life on land, including vertebrates and plants ~360 mya first reptiles 200 - 250 mya first mammals and birds

16. Gondwanaland – 650 – 475 mya – oldest continuous land mass

17. N. Amer. and N. Europe (PA) begin drift north

18. NA, N. Europe & Siberia eventually collide to form Laurasia Gondwanaland drifts north

19. W. Asia and Europe collide – Ural Mtn.; other continents join to form Pangaea; East Asia isolated, Tethys Sea; One great ocean – Pathalassa Permian – time of great terrestrial and marine connectivity but were barriers – Central Pangaean Mtn. range; Pangaean Desert

20. Break up of Pangaea Formation of Pangaea brought together biota formerly isolated Diversification of Pangaea and Pathalassa probably resulted from breakup (180 mya) by creating isolation Breakup began when Turgai Sea expanded from Arctic to split Asia and Euramerica Separation N. America and Europe by shallow “Atlantic Sea”

21. Break up of Pangaea Tethys Seaway opened Gulf of Mexico formed with separation of N. and S. America

24. N. America and Europe reconnect (Beringea landbridge) NA epicontinental sea

25. M and I separate; I moves toward Asia (collide ~60 mya); AU separates from Antarctica severing link to S. Amer. Many small plate collisions (65 – 2 mya)

27. Great American Interchange – reconnected NA and NT ~4 mya (last connected ~160 mya)

30. Hotspots – fixed, weak points in crust

31. Epicontinental (Epeiric) Seas Changes in continent location and sea levels Formed barriers on terrestrial landscape Australia divided into three parts in Cretaceous (50 mya) North America – several epeiric seas – most recent ended ~65 mya Europe and Asia separated by Turgai Sea until ~30 mya

32. Paleoclimate Relative amount of land/ocean and distributions also influence solar radiation and temperature  climate, winds, and currents Example – warm circum-equitorial currents (Tethys Seaway) replaced by cold currents

36. Consequences of Plate Tectonics Profound effects on both terrestrial and aquatic biota Constant, albeit slow, change –Plates form, expand, merge, separate –Plates eliminated by subduction and consumed –Change shape These dynamics allowed flow but also isolation through barriers

38. Effect of lowering sea level on marine diversity (loss of seas

39. Seafloor spread and number of species

40. Boxes in this chapter rich with information. Among most useful are Tables 8.2 and 8.3