Ch. 9 Review. Pgs #1-31 Write Questions and Answers

Transcription

1 Ch. 9 Review Pgs #1-31 Write Questions and Answers

2 #1-5 Answers 1. The layer of the upper mantle that can flow is the: A - Asthenosphere 2. Most scientists rejected Wegener s theory of continental drift because the theory failed to explain: D How the continents move 3. Subduction of the ocean floor takes place at: D - Trenches 4. Two plates collide with each other at: B A convergent boundary 5. A fault in which the hanging wall slides up and over the footwall is a: A Reverse Fault

3 # 6-10 Answers 6. The earth s outer core is made of basalt and granite: False Crust 7. The spinning of the asthenosphere, made of iron and nickel, explains why Earth has a magnetic field: False Inner Core 8. Magnetic strips on the ocean floor are where oceanic crust sinks back to the mantle: False Deep Ocean Trenches 9. When two continental plates converge, a rift valley appears: False Diverge 10. Land subsidence occurs when Earth s surface sinks as a result of geologic processes: True

4 How is the inner core different from the outer core? The inner core is a dense ball of solid iron and nickel that spins. The outer core, by contrast, is a layer of molten iron and nickel that behaves like a thick liquid. 12. Explain why there are convection currents in the mantle. Heat from the Earth s core heats the mantle. Some mantle material is soft and can bend like plastic. Over time, this material can flow slowly, forming convection currents.

5 How does a hot spot form a volcanic island? At a hot spot on the ocean floor, magma from the mantle melts through the crust, forming a volcanic island. 14. What evidence of Earth s climate in the past supports the hypothesis of continental drift? Evidence includes fossils of tropical plants found in polar regions and scratches made by continental glaciers found in places with mild climates.

6 What was the importance of the discovery that molten rock was coming out of cracks along the mid-ocean ridge? The importance of that discovery is that it supported the theory that of sea-floor spreading. It also led scientists to look again at Wegener s theory of continental drift. 16. Describe the processes that create a faultblock mountain. When tension caused by plate movements is great enough to break the crust, normal faults form. Along these faults, blocks of crust can slide, creating a faultblock mountain.

7 What happens when a plate of oceanic crust collides with a plate of continental crust? Why? Oceanic crust is more dense than continental crust. As a result, when a plate carrying oceanic crust collides with a plate carrying continental crust, the oceanic plate sinks beneath the continental plate (subduction) 18. Interview with Alfred Wegener Should include mentions of evidence he used, such as fossils, landforms, and climate evidence.

8 Classify the layers of the earth. Solid Crust, Lithosphere, Inner Core Solid but able to flow slowly Asthenosphere Liquid Outer Core 20. Comparing and contrasting oceanic and continental crust. Both are parts of Earth s outer layer. Continental crust consists of less dense rocks such as granite. Oceanic crust consists mainly of denser rocks such as basalt.

9 What do geologists think is the driving force of plate tectonics? Explain. Convection currents in the mantle. The currents rise through the asthenosphere, then spread out beneath the lithosphere, dragging the overlying plate along. 22. What events can cause land subsidence and what is formed as a result? Geologic processes such as diverging plates or tension in the crust can cause land subsidence. With diverging plates the result may be rift valleys or ocean basins.

10 State in one sentence the most significant discovery geologists found through their study of plate tectonics. Answers vary. Example: Pieces of Earth s lithosphere are in constant, slow motion, driven by convection currents in the mantle. 24. A community has just built a street across a strike-slip fault that has frequent earthquakes. How will movement along the fault affect the street? Where the street intersects the fault, the street will eventually be broken and the segment will be moved sideways.

11 The part carrying Australia is moving to the northeast; the part carrying India is moving to the North 26. Because the parts are moving in different directions, a divergent boundary will form 27. This is a convergent plate boundary between two continental plates. Mountains should form.

12 The arrow at A represents: D Molten magma rising from the mantle 29. What is occuring at the feature labeled B? F New rock is being added to the oceanic plate 30. As sea-floor spreading occurs, the oceanic plate: C Moves from B to C 31. What is occuring at D? G The oceanic plate is melting as it sinks into the mantle.