GEO8 DISC
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School
University of California, Riverside *
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Course
008
Subject
Geology
Date
Apr 3, 2024
Type
Pages
7
Uploaded by SuperHornet3448
Winter 2024 GEO008 Page 1 of 7
Activity 2 – Plate Tectonics (100 points)
This week we are learning all about plate tectonics and where earthquakes occur around the globe. We will learn the basics of plate tectonics, including locations of the plate boundaries, distribution of earthquakes, and bathymetry and topography. This exercise uses images from Google Earth and Google Earth overlays created by various members of the scientific community. Updated seismic data can be found at: http://earthquake.usgs.gov/earthquakes/map/ Section A: Please refer to the following worldwide maps of earthquakes and volcanoes. Global Earthquakes (Note: Shallow, Intermediate, and Deep) refer to how deep underground the earthquakes are. It isn’t crucial for Tarbuck and Lutgen, The Earth (4
th
ed.)
, Macmillan, 1993
Winter 2024 GEO008 Page 2 of 7
Questions 1. Describe how the earthquakes and volcanoes are distributed around the world. Please list at least 4 geographic location.
(12 pts) 2. List and define the three main types of plate boundaries. (18 pts) http://www.hrw.com/science/si-science/earth/tectonics/volcano/volcano/index.html
Global Volcanoes
Winter 2024 GEO008 Page 3 of 7
3. Name at least 5 major tectonic plates. (10 pts) Section B:
The Atlantic Ocean Figure 1:
Shown is the mid-Atlantic Ocean region of the globe. The bathymetry of the sea floor is shown with dark blues representing deeper ocean water and light blue representing shallower ocean water. Topography of the continents is also shown with light green representing elevations near sea level and warm colors (yellow and reds) representing high elevations. Solid lines show the plate boundaries. Dots give earthquake locations and are colored by depth beneath the surface of the Earth (red = shallow and blue = deep).
1. Where is the plate boundary located that separates the South American and African Plates? (5 pts) 2. If the boundary were not shown (no solid lines on map) how might you determine the location? (5pts) 3. Where do most of the earthquakes in the Atlantic Ocean occur? Are they shallow or deep? (5 pts)
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Winter 2024 GEO008 Page 4 of 7
Figure 2: The age of the sea floor is shown for the mid-Atlantic Ocean. Young/recent sea floor ages are shown by warm colors (orange and red) and old sea floor ages are shown by cool colors (blue). 4. Describe how the sea floor age changes as you go from the east coast of South America toward the plate boundary. (5 pts) 5. Describe the relationship between sea floor age, bathymetry (look at figure 1), and the mid-
Atlantic plate boundary. (5 pts) 6. Is crust being created or destroyed at this plate boundary? Is this plate boundary divergent, convergent, or transform? (5 pts)
Winter 2024 GEO008 Page 5 of 7
New Zealand Figure 3: Map of the Tonga-
Kermadec plate boundary, located just north of New Zealand. The bathymetry of the sea floor is shown with dark blues representing deeper ocean water and light blue representing shallower ocean water. The plate boundary that runs through Kermadec and Tonga is where the light blue transitions to the deepest blue from left to right. Earthquakes are shown by circles and earthquake depths ranges are shown by circle color : red (0-10 km), orange (10-20 km), yellow (20-30 km), light green (30-50 km), blue-green (50-100 km), light blue (100-200 km), blue (200-400 km), dark blue (400+ km). 7. (a) How do the depth and distribution of earthquakes shown for the mid-Atlantic plate boundary (see Figure 1) differ from those of the Tonga-Kermadec plate boundary shown above? (5 pts)
Winter 2024 GEO008 Page 6 of 7
(b) Draw a cross-section of earthquake depth versus distance along a profile perpendicular to the plate boundary just beneath the “Tonga” label (i.e., along the red line in the figure above). Include where the main plate boundary is located and note there is a scale on the bottom of the map to assist with your distance vs. depth plot. (5 pts) 8. Why do you think the earthquakes happen at these locations and depths? In other words, what can you infer about the location of the earthquakes by the pattern of earthquake distribution in the cross-section? What is the pattern of earthquakes along the subduction zone called? (5 pts) 9. Is crust being created or destroyed at this plate boundary? Is this plate boundary divergent, convergent, or transform? (5 pts)
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Winter 2024 GEO008 Page 7 of 7
Simple calculation on spreading center 10. A spreading center has a spreading rate of 6 mm/yr. How old (in millions of years) would you expect a rock to be if you found it 200 km from the spreading center? (Hint—if 6 mm/year is the spreading rate, how quickly is each side moving away from the spreading center?) Please show all the steps. (10 pts)