海洋科學：地質面向

1. 海洋科學：地質面向 Birth of an island

2. The Earth in cross section

3. The chemical and physical organization of the Earth’s Layers compared

4. The layering of the lithosphere and asthenosphere in more detail

5. Characteristics of the Earth’s Layers

6. 大陸飄移假說（Continental Drifting Hypothesis）→海底擴展學說（Seafloor Spreading）→板塊構造學說（Plate Techtonics）

7. Seismic events worldwide, January 1977 through December 1986

8. The fit of all the continents around the Atlantic

9. Reconstruction of Pangaea

10. The major lithosphere plates

11. 板塊構造學說（Plate Techtonics）

12. An overview of the plate tectonics process

13. The formation of a new plate boundary:the breakup of Pangaea

14. The South Atlantic in cross section, showing the mid-ocean ridge at a divergent plate boundary

15. A cross section through the west coast of South America

16. The formation of an island arc along a trench as two oceanic plates converge

17. The convergence of two continental plates

18. Characteristics of the Plate Boundaries

19. A long transform plate boundary

20. Key Concepts for Plate Tectonics (I) • Earth is composed of concentric spherical layers, with the least • dense layer on the outside and the densest as the core. • The lithosphere, the outmost solid shell that includes the crust, • floats on the hot, deformable asthenosphere. The mantle is the • largest of the layers. • Large regions of Earth’s continents are held above sea level by • isostatic equilibrium, a process analogous to a ship floating • in water. • Some seismic waves – energy associated with earthquakes – can • pass through the Earth. Analysis of how these waves are changed, • and the time required for their passage, has told researchers much • about conditions inside Earth.

21. Key Concepts for Plate Tectonics (II) • Plate tectonics theory suggests that Earth’s surface is • not a static arrangement of continents and ocean, but a • dynamic mosaic of jostling segments of lithosphere • called lithospheric plates. The plates have collided, • moved apart, and slipped past one another since • Earth’s crust first solidified. • Plate motion is driven by slow, heat-generated • (convection) currents flowing in the mantle. Most of the • heat is generated by the decay of radioactive elements • within Earth.

22. Key Concepts for Plate Tectonics (III) • Most of the large-scale features seen at Earth surface • may be explained by the interactions of plate tectonics. • Plate tectonics also explains why our ancient planet has • surprisingly young seafloors, the oldest of which is only • as old as the dinosaurs, that is, about 1/23 the age of • Earth. • The confirmation of plate tectonics rests on diverse • scientific studies from many disciplines. Among the • most convincing is the study paleomagnetism, the • orientation of Earth’s magnetic field frozen into rocks • as it solidified.

23. The End Thank you for your attention (if you have been staying awake)