Structure of the Earth

1. Inside the Earth 1:34 What is the earth like below its surface? Structure of the Earth What makes up the interior of our planet? Compiled by Susan Weidkamp

2. Chapter 22 Objectives To observe how change is dependent on depth. • The chemical makeup of the earth changes as you go deeper. • The density of materials increase with depth. • Temperature and pressure increase with depth. To explain why these changes are observed. To learn how models are used in science.

3. Earth has a few well kept secrets

4. Chemical vs.Physical Chemical layers refer to the composition or make up of the earth’s interior. Physical Layers refer to the state of matter such as solid, liquid , or in between called “plastic.”

5. 6. The MohoBoundary Found between the chemical layers of the crust and the mantle. AndrijaMohorovicic (Mo-ho-ro-vi-chic) discovered a boundary between the crust and the mantle. The boundary is now known as the “Moho,” or “Mohorovicic Discontinuity.”

6. 7. Roughly, how hot is the Earth’s core?

7. Layers of the Interior of an Egg Physical Layers of an egg: Chemical Layers of an egg: Crust-solid Crust-CaCO3 Egg white- Liquid Egg white- amino acids &proteins Yolk- Liquid Yolk- Lipids Fatty acids

8. How do the chemical layers change in an egg as you go deeper? The type of compound changes from calcium carbonate, CaCO3 to Proteins and the inner yolk is mostly lipids or fat. How do the physical layers change in an egg as you go deeper? The state changes from outer rigid solid to liquid egg white and yolk.

9. Interior of the Earth Compare the physical layers on right to the chemical layers. How are they different? How are they similar? MOHO

10. 8. How do the chemical layers change in the Earth as you go deeper? The type of material changes from compounds like silicates to a core of mostly elemental and metallic iron. 9. How do the physical layers change in the Earth as you go deeper? The state changes from the outer rigid crust a solid, to the plastic asthenosphere to the liquid core and the inner solid core.

11. Why are there more physical layers than chemical layers? 10. Chemical layers: Crust- Silicates of Al, Fe and Mg Mantle-Silicates of Fe and Mg Core- Metallic Iron 11. Physical layers: Lithosphere –rigid solid Asthenosphere- plastic Mesosphere- solid Outer Core- Liquid Inner Core- Solid

12. Scale of the Interior

13. How does the temperature change the deeper you go? The change in temperature and pressure affect the state of the interior of the Earth and density probably has the most effect on the chemical layers.

14. Check your neighbor • How do the chemical layers change as you go deeper? • How do the physical layers change? • Name the chemical layers: • Name the physical layers: From compounds to elements, and by density. From solid to plastic to liquid to solid due to temperature and pressure. Crust, mantle, core Lithosphere, asthenosphere, mesosphere, & core

15. How do we really know what the center of the earth is like? We have to make an educated guess… Or we go to the movies!

16. Ch. 22 Objectives Part 2 • How do scientists study the earth’s interior? • Identify two types of seismic waves. • Explain how scientists make inferences about the earth’s core. • Infer characteristics of an object through indirect observation.

17. Indirect observations Example #1 WIND • When you do not actually observe the wind, you see only its effects as the branches of a tree move. The moving branches are the indirect observation. The wind is the inferred characteristic.

18. What is the core of the earth like? • Creamy Chocolate • Chewy Nougat • Soft Caramel • Hard “Rock” Candy

19. What is the deepest hole in the earth?12,345 meters or 7.67 miles Sakhalin-1

20. Density Puzzle Inference #1 • Density of the earth equals the earth’s mass divided by its volume, or 5.5 g/cm3 • Average rocks found in the crust have a density of 3.5 g/cm3. • What must be the core’s density, • more than 5.5 or • less than 5.5? Core must me more to average 5.5 g/cm3

21. Light energy waves bend Light will bend and reflect at the interfaces between different materials. Do seismic energy waves bend like light? Yes!

22. P waves are PRIMARY WAVES They travel like a slinky. They are the fastest, and are called: S waves are shear or SECONDARY WAVES They travel like a snake. They are second fastest and are called: Seismic Waves Compression Waves Transverse Waves http://www.geo.mtu.edu/UPSeis/waves.html

24. Inference # 2 Earth’s Interior has several layers. Evidence: P-waves bend at every new layer. S-waves bend in solid layers, but stop at liquid layers

25. The MohoBoundaryInference #3 Between the chemical layers of the crust and the mantle. AndrijaMohorovicic (Mo-ho-ro-vi-chic) discovered a boundary between the crust and the mantle. He found seismic waves speeded up at a depth between 30-35 km below the surface. Why would they speed up? A. The earth becomes hotter the deeper you go. B. The earth becomes denser the deeper you go. C. The pressure increases so particles are closer together. The boundary is now known as the “Moho,” or “Mohorovicic Discontinuity.” http://www.infp.ro/Labs/file2.htm

26. Evidence from Seismic Waves Recordings of seismic waves from earthquakes gave scientists a puzzle: A shadow zone (no waves) appeared at 105 degrees.

27. Slower, Shear, S waves offer a clue Transverse waves (S waves) as cannot travel through liquids. Liquids have weak forces of attraction between the particles, and these waves break up when they arrive. This explains why there is a large “S” SHADOW ZONE.

28. Seismic waves bend as they pass through interior; this creates ashadow zone. The p shadow zone indicates the size of the core. The s shadow zone indicates the physical state of the outer core- liquid. Inference # 4Evidence of the earth’s core

29. The Shadow Zone Puzzle • The area beyond 105 degrees distance forms a shadow zone. At larger distances, some P waves would arrive, but still no S waves. • Only slow traveling surface waves reach this area traveling through a thin layer of crust. 105 Seismic waves bend at an interface, or chemical layer.

30. Inference #5 How big is the Earth’s core? Using the 105 degree angle of the shadow zone, and the Earth’s radius of about 6350km, draw a a right triangle. Then calculate: Radius of core 6350 km = cosine of 52.5 degrees Cosine of 52.5 = .60876 Core’s radius = 3870km (52.5 degrees is half of 105 degrees, and cosine = adjacent / hypotenuse)

32. IRIS video Clip explaining shadow zone Turkey Part II

33. Propagation of Seismic Waves

35. How Earthquakes are located

36. Seismic Wave Analysis The time between the two arrivals is exactly 10 seconds. The ratio of velocities is 8.7 km/sec. The product of these two values = 87 kilometers or the distance between the seismometer and the earthquake.

37. Using a Time-Distance Graph

38. Check your neighbor • How did scientists discover the Earth’s core? • How are P waves different from S waves? • What clue’s did the shadow zone tell us? • About how big is the Earth’s core? • Where is the “Moho” found? Between the crust and the mantle (6,378-5,100 =1,278 km or so)

39. Physical Layers Lithosphere - Lithos = “Rock, or stone” Asthenosphere-Sthenos = “strong,” asthenos = not strong ( prefix “a” negates)

40. The Lithosphere Oceanic Crust- usually found under oceans, and near the edge of continents. Continental Crust-usually found in continents, forming plains, and mountains.

41. Coast of the UK

42. Oceanic Crust Oceanic crust is mostly made of dark rocks like basalt and gabbro.

43. Continental Crust Continental crust is less dense than oceanic crust. It contains more silicon, oxygen and aluminum. Most of the rocks are made of granite and rhyolite.

44. What causes new crust to form? What causes the volcanoes in the Pacific Rim?

45. Last Oregon Tsunami 1700

46. Movement in the Asthenosphere Less Dense How do temperature changes affect the movement of matter in the mantle? Hot matter rises, cools then sinks back.

47. Convection Cell

48. Convection Currents Interior of Earth

50. Plume rising through a layered viscosity mantle The plume encounters a change in viscosity. It passes from the lower mantle to the upper mantle. Now under less pressure, it becomes thinner (less viscous) and faster.