Oceanography Lab 2A
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Northern Virginia Community College *
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111
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Geography
Date
Apr 3, 2024
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docx
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2
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1.Survey the ocean floor relief in the two views of Figure 2A-1, especially from coasts to deeper waters. Color coding denotes water depth, showing that as ocean depth ______ blue becomes darker. (Land topography is also displayed, and as elevation increases, greens transition to tan and then darker brown.)
increases
2.In the top image, find the feature in the center of the Atlantic Ocean. This is the Mid-Atlantic Ridge. Based on the color coding, is the Mid-Atlantic Ridge deeper or shallower than the ocean floor on either side?
It is shallower.
3.How does the Mid-Atlantic Ridge compare to the surrounding landmasses, specifically Africa?
The feature mirrors the western coastline of Africa.
4.The Mid-Atlantic Ridge features a deep, narrow central rift valley following a central axis. Magma seeps upward along the rift and adheres to the edge of either side of the ridge. The new material pushes each plate away from the central axis. What is happening at the oceanic ridge?
It is a location where new crust forms.
5.In Figure 2A-2, the Mid-Atlantic Ridge has red arrows denoting the motion of each plate along
the boundary. The Mid-Atlantic Ridge is a ______ plate boundary.
divergent
6.Center the globe on South America’s west coast. The darkest blue reveals an oceanic trench, the Peru-Chile trench. The trench is deepest off the ______ portion of South America’s western coast.
central
7.Refer to Figure 2A-2 and examine the direction of tectonic plate motion along the western margins of South America, Central America, and the Aleutian Islands. What is the dominant type
of plate boundary that forms in this area?
Convergent
8.What other evidence supports that North and South America, Europe, and Africa once were connected?
Similar jigsaw-like shapes
9.Locate Iceland on Figure 2A-2. What is the significance of the location of the island on the boundary between the North American and Euroasian plates?
It is an active area of divergence.
10.Within the abutting plates along the Mid-Atlantic Ridge, the crust migrates away from the ridge as new material is added. Therefore, westward toward the east coasts of Greenland and North America, the age of the oceanic crust ______.
increases
11.Compare Figure 2A-2 with Figure 2A-3. Earthquake activity along the west coast of South America is primarily ______ of the trench, where a denser oceanic plate is being subducted under a less dense continental plate.
on the land side
12.Coasts are tectonically active (near a plate boundary) or passive (site of sediment deposits). The western United States lies along the Pacific plate and is tectonically active. The east coast of North America is a ______ margin because the continental crust and oceanic crust lie on the same plate.
passive
13.In the NOAA animation, the age of the crust is color coded with red as the youngest and blue as the oldest. The youngest ocean crust is associated with ______ plate boundaries (for example, the Mid-Atlantic Ridge).
divergent
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