Intro to Earth’s structure and Plate Tectonics

1. Intro to Earth’s structure and Plate Tectonics

2. Shape of the Earth Rotation Gravity Oblate Spheroid

3. Refraction and reflection of seismic body waves - ray paths Seismic ray paths in a layered Earth Seismic ray paths if Earth were homogeneous

5. Inside the Earth

6. D”

7. Plate Tectonics • Unified the study of the Earth (geology,seismology, marine geophysics,…) • Why is the Earth restless? (earthquakes, volcanoes, mountain ranges) • Answers “old” questions: Why do earthquakes and volcanic eruptions occur in specific areas?

8. the principle of isostasy Mechanical Layers Lithosphere • Crust and mantle • ~100 km thick • Hard • Crust floats on top Asthenosphere • Soft • ~300 km thick

9. By plate we really mean a “shell” on Earth’s surface that is about 100-200 km thick and includes all of the crust, and the uppermost part of the mantle. • Tectonics is the term we use in geoscience to represent the formation of folds, fractures, faults, etc. in rocks.

10. Plate Tectonics Says that the earth’s crust and upper mantle are composed of several large, thin, relatively rigid plates that move relative to one another Plate Tectonics is the term for the processes associated with the creation, movement,and destruction of the plates.

11. Lithosphere plates are large slabs of the crust and upper mantle that move horizontally relative to one another. Velocities in cm/yr Keller, 2002

13. zoom in on U.S.-west coast

15. Plate tectonics is the overarching model which allows us to understand many global phenomena observed within, on, and above the solid earth Keller, 2002

16. Plate boundaries and earthquakes Nasa cumulative earthquakes 1960-1995

17. 3 types of plate boundaries Iceland = a mid-ocean rift above water! a continental rift turned mid-ocean rift 1: divergent plate boundary a) mid-ocean rift b) continental rift

18. 1: divergent plate boundary Iceland: a mid-ocean rift above water!

19. 1: divergent plate boundary Iceland: a mid-ocean rift above water! Krafla, 1980 Thingvellir: site of first parliament in 930 A.D.

20. 1: divergent plate boundary Iceland: a mid-ocean rift above water!

21. Oman Ophiolite A former mid-ocean ridge now on land

22. 1: divergent plate boundary East-African Rift Zone: a continental rift Oldoinyo-Lengai eruption, 1966

23. Rifting earlier in Earth’s history The breakup (and rotation of Africa and S-America)

24. 3 types of plate boundaries subduction zone 2: convergent plate boundary a) ocean-continent

25. Examples of subduction zone products Turrialba Volcano in Costa Rica Photo by Regina Small, student in this class (GEO 1001 Sec 002 – spring 2006)

26. Examples of ocean-continent subduction zone products Cascades volcanism Mt. St. Helens (January, 23, 2006 – Dave Sherrod, USGS) Mt. St. Helens, spring 1980

27. 400 km 200 km 0 km West Eurasia Plate 200 km Pacific Plate depth 400 km Cross-section through Japan area Depth of Earthquakes in subduction zones East

28. In addition to subduction and volcanism there can be uplift of crust due to convergent plate motion Limestone in the Andes

29. 2: convergent plate boundary (continued) Mt. Everest S N India Tibetan Plateau b) continent-continent

30. Himalayas – the result of the convergence of two continental plate boundaries Mt. Everest

31. 3.) Transform Boundary (Strike Slip Faults)

32. Strike-slip fault Alpine fault, New Zealand

34. Cumulative volcanic eruptions 1960-1995 Nasa

36. Plate Boundaries also uplift