Using the power of Google Earth, GeoTours take you on flyovers of key locations discussed in the text.
StudySpace student website and ebook icons in each GeoTour connect your to the text and online review materials.
Dialogue boxes accompanying each site include text, figures, photos.
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Geotour 2: Plate Boundaries
Continental Drift |
| 1a. Check the box next to “Seafloor Age Map” in the Worksheet 2 folder to view the ages of the oceanic crust around the world. Note that you can use the transparency slider to make this overlay less opaque.
Check and double-click the placemarks for Problem 1 to fly to a location above the Atlantic Ocean. These placemarks represent conjugate points (locations on the opposite sides of an ocean that were once adjacent before seafloor spreading occurred). Although the fit between the African and South American coastlines had been recognized for some time, Wegener carefully matched continental shelves to improve this fit. Use the Measuring Tool to determine how far these points have moved apart (in km). Zoom in and use the Path tab to create segments along the fracture lineation that offsets the colored ages of the ocean floor.
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| 1b. Using the seafloor age map, about how many millions of years ago were these points once adjacent?
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| 1c. Using the largest number of the range for your answer to 1b and using the distance for your answer to 1a, calculate the average spreading rate for these points in km/Ma.
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| 1d. Express your average spreading rate answer for 1c in terms of cm/yr. Note: If the plates are moving apart symmetrically at the same rate (i.e., the color band widths are approximately equal), then 1/2 of this answer is the average rate at which the South American plate is moving west and the African plate is moving east.
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Divergent Boundaries
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| 2a. Check the box next to “Seafloor Age Map” in the Worksheet 2 folder to view the ages of the oceanic crust around the world.
The placemarks for Problem 2a lie on the crest of a mid-ocean ridge (a divergent boundary) in the Atlantic and Pacific Oceans, respectively. Double-click each placemark and use the color bands representing seafloor ages to determine which divergent boundary is spreading at a faster rate.
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| 2b. Some divergent boundaries spread at different rates. Double-click on the Problem 2b placemark to fly above the East Pacific Rise. Use the color bands representing seafloor ages on either side of this mid-ocean ridge to determine which side is moving faster.
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| 2c. In the Layers panel, turn on Borders and Labels and also Gallery > Volcanoes, then double-click on placemark Problem 2c. Divergent boundaries often begin as triple junctions comprised of three “arms” at ~120° apart that may or may not evolve into divergent boundaries. Which of the statements below about this area is incorrect?
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Convergent Boundaries
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| 3a. Check the boxes next to “Seafloor Age Map” and “Earthquakes” folders in the Worksheet 2 folder to view the ages of the oceanic crust around the world and selected 1986-2005 earthquakes color-coded by depth, respectively. Also, in the Layers panel, turn on Borders and Labels and Gallery > Volcanoes.
Check and double-click placemark Problem 3a to fly to the Mariana Trench. Which of the following is incorrect?
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| 3b. Subduction ultimately produces a volcanic arc on the overriding plate (placemark Problem 3b). What depth of earthquakes lies beneath the volcanic arc associated with the Mariana Trench?
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| 3c. Use the Measuring Tool to determine the arc-trench gap (distance between the volcanic arc and the trench axis, in km) between the placemarks of Problem 3c.
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| 3d. Check and double-click placemark Problem 3d to fly to the Tonga Trench. What depth of earthquakes lies beneath the volcanic arc associated with the Tonga Trench?
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| 3e. Use the Measuring Tool to determine the arc-trench gap (in km) between the placemarks of Problem 3e.
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| 3f. Check and double-click placemark Problem 3f to fly to South America. What depth of earthquakes lies beneath the volcanic arc associated with this subduction zone?
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| 3g. Assume that the earthquake depths define the Wadati-Benioff zone for the subducting slab. Compare your answers to Problem 3b, 3d, and 3f and choose the statement that best describes your observations.
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| 3h. Given your answer to 3e for the Tonga Trench and your answer for 3g (use an average), calculate the angle of descent for the subducting slab using the following formula: angle of slab descent = arctan (depth of slab beneath arc/arc-trench gap).
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Transform Boundaries
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| 4a. Check the boxes next to “Seafloor Age Map” in the Worksheet 2 folder to view the ages of the oceanic crust around the world. Also, in the Layers panel, turn on Borders and Labels as well as Gallery > Earthquakes.
Check and double-click the placemarks for Problems 4a-i, -ii, and -iii to fly to the Mid-Atlantic Ridge. These placemarks either point to a segment of an active transform fault or of an inactive fracture zone (see your textbook if you don’t recall what these are). Which of the following statements is correct?
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| 4b. Which direction are the placemarks for Problem 4b-i and 4b-ii moving, respectively?
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| 4c. Which direction are the placemarks for Problem 4c-i and 4c-ii moving, respectively?
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| 4d. Check and double-click the placemark for Problem 4d. Given the offset shown here, what type of transform fault is the San Andreas Fault?
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Hot Spots
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| 5a. Check the boxes next to “Seafloor Age Map” in the Worksheet 2 folder to view the ages of the oceanic crust around the world. Also, in the Layers panel, turn on Borders and Labels as well as Gallery > Volcanoes.
Check and double-click the folder Problem 5 to fly to the Pacific Ocean where you will have a view of the Hawaiian Island-Emperor Seamount hotspot chain with their age of formation (Ma). Use the Measuring Tool to measure the distance between Midway Atoll and Kilauea and calculate the average velocity of the Pacific Plate in cm/yr.
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| 5b. What is the approximate age of the bend in the Hawaiian Island-Emperor Seamount chain?
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