Exploring Earth's Structure: Crust, Mantle, and Core

1. Earth Science And the Ocean Part I

2. PLate Tectonics: The Structure of the Earth

3. Plate Tectonics Topics: Structure of the Earth Plate Boundaries Driving Mechanisms of Plate Tectonics

4. Structure of the Earth The Earth can be considered as being made up of a series of concentric spheres, each made up of materials that differ in composition . We will Focus on 4 Layers

5. Crust and Lithosphere Has the average composition of basaltic rock (Basalt) that is rich in silica and magnesium. Crust: the outermost layer of the earth, a hard outer shell. Crust beneath the oceans and the continents is different: Oceanic crust: relatively thin, varying from 5 to 8 km (but thinner at Oceanic ridges) yet denser.

6. Continental Crust: thicker than oceanic crust but it is less dense Has the average composition of granitic rock (Granite). Thickness ranges from 20 km to about 75 km (beneath mountain ranges).

7. Lithosphere: The topmost layer of the upper mantle. The Lithosphere is more viscous (fluid) than any other part of the mantle. This is what the crustal plates are sitting on. Due to its elasticity and convection we have plate movement

8. The crust and lithosphere are broken up into 25 Lithospheric Plates USGS

9. Oceanic Vs Continental

10. Continental Crust is _____ Oceanic Crust • Older than • Younger than • The same as • None of the above

11. Continental Crust is made of • Granite • Feldspar • Basalt • Quartz

12. Oceanic Crust is ______ Continental Crust • Thinner than • Thicker than • The same as

13. Oceanic Crust is made of • Granite • Feldspar • Basalt • Quartz

14. The Mantle includes the Lithosphere. Upper Mantle or Lithosphere: near its melting point so that it behaves like a plastic (Similar to Silly Putty ); the upper mantle material is more fluid Upper mantle material MOVES by convection; transfers heat from within the Earth towards the surface. Lower Mantle: solid material, rather than plastic.

15. The Core: the metallic portion of the Earth; Iron mixed with small amounts of Nickel. It is at the center Outer Core: probably liquid (based on studies of shock wave passage through the Earth). Inner Core: solid, made up of cooled liquid core material.

16. In a Nutshell……. • The Earths interior is composed of 4 main layers. • The Crust the outermost layer. • Oceanic Crust Thinner, Denser, Younger and made of Basalt. • Continental Crust Thicker, Older, Less Dense and made of Granite. • The Mantle which includes the Lithosphere which is just under the crust. Largest of the layers • It is composed of molten rock which has the consistency of Silly Putty. • The Core Fe Ni inner core (solid) and a liquid outer core also made of nickel and iron.

17. The Outermost layer of the Geosphere is the • Inner Core • Outer Core • Mantle • Crust

18. There are ____ Crustal Plates • 10 • 1 • 13 • 25

19. The Crustal plates sit or “Float” on top of the • Inner Core • Lithosphere • Crust • Outer Core

20. The Lithosphere is part of the • Crust • Inner Core • Outer Core • Mantle

21. Plate Boundaries

22. Plate Boundaries The types of boundary movement between plates are distinguished by the type of relative plate motion along the boundary: Oceanic Ridge – Divergence Oceanic Trench – Convergence Transform Margins – Horizontal slip

23. Oceanic Ridge

24. More-or-less continuous volcanic mountain chain throughout the world's oceans. A kilometre deep valley runs along much of the length of the ridge. 65,000 km long. Average width approx. 1,000 km. Rise up to 3 km above the surrounding sea floor. Average depth approx. 2.3 km below sea level.

25. The ridge is a Divergent Plate Margin and divergence takes place by Sea Floor Spreading. New crust is added from upwelling magma (molten rock) from the upper mantle. From http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html Older crust is pushed laterally away from the ridge axis – so that the sea floor spreads away from the ridge axis.

26. Oceanic crust becomes older with distance from the oceanic ridge. Spreading rates (distance per year that two points on either side of a ridge move apart) vary: N. Atlantic Ridge 3cm/yr S. Atlantic 5cm/yr N. Pacific 12.5cm/yr E. Pacific 17.5 cm/yr

27. http://www.gisdevelopment.net/technology/images/image002.gif

28. Divergent Boundaries Summary • Crustal Plates are moving Away from each other at this boundary. • Most well known is the “Mid Atlantic Ridge” • Largest Geological structure on Earth • Area of sea floor spreading – The Atlantic Ocean is getting bigger. • Can be found on land in the country of Iceland • Definitive Proof of Crustal Plate Movement -through Paleo Magnetism of rock.

29. The mid Atlantic Ridge is a ____________ plate boundary • Divergent • Convergent • Transform • Integral

30. The largest geological structure on Earth is • The Grand Canyon • Mid Atlantic Ridge • Challenger Deep • Mount Everest

31. The Atlantic Ocean is getting • Smaller • Bigger • Deeper • Shallower

32. The only place on Land you can see the Mid Atlantic Ridge is • Ireland • Greenland • Iceland • Norway

33. At divergent plate boundaries the plates are moving • Toward each other • Away from each other • Sliding past each other • down

34. Convergent Plate Boundaries

35. Oceanic- Continental • Oceanic – Oceanic • Island Arcs (talk more about this later) • Trenches

36. Oceanic Crust – Continental Crust Basaltic oceanic crust descends beneath lighter continental crust. Coastal mountain chains develop due to compressive forces and volcanics (e.g., the Andes of South America). Magma material rises from descending slab and builds volcanoes in the rising mountains.

37. Crust descends at angles from 35 to 90 degrees. Crust melts as it descends, beginning at 100 to 200 km depth and has melted completely by 700 km depth. The zone over which melting takes place is termed the Benioff Zone.

38. Melting crust rises and penetrates overlying crust to form volcanoes. Material (sediment and basaltic rock) is scraped off the subducting crust and accreted to the over-riding crust – termed the subduction complex.

39. Oceanic Trenches

40. Trenches

41. Thousands of kilometers long, 50 to 100 km wide and several kilometers deep (below sea level). Longest trench: Peru-Chile trench at 5,900 km. Deepest trench: Mariana trench (western Pacific) at 11 km deep (almost 7 MILES deep)

42. Trenches are termed Convergent Plate Margins because they are locations where plates converge on, or push against, each other. Where oceanic crust is subducted back into the upper mantle.

43. Island Arcsparallel many oceanic trenches: arc-shaped chains of volcanic islands (e.g., Japan) due to the rising magma from melting subducted crust.

44. When one plate moves under another plate. This is called • Induction • Deduction • Subduction • Abduction

45. Older Oceanic Crust will move __________ Younger Crust • Over • Under • Sideways to • Into

46. Island Arcs form Parallel to Oceanic Trenches • True • False

47. The deepest trench is the • Marianas Trench • Tonga Trench • Japan Trench • Peru –Chile Trench

48. The longest trench is the • Tonga Trench • Peru- Chile Trench • Marianas Trench • Kermadec Trench

49. Continental Crust will subduct under Oceanic Crust. • True • False

50. The Area where the Oceanic crust is “melted” back into the Magma is called the • Benihoff Zone • Melt Zone • Magma Deep • Trench Zone