160L_Wk4_platetectonics-1
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California State University, Long Beach *
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300
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Geology
Date
Apr 3, 2024
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docx
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Lab 4: Plate tectonics and plate movement rate
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Part 1
How do plates move?
Density differences between plates control whether a plate can sink into the mantle at subduction zones. Convection in the mantle moves the plates. To explore density and how it works. We will work with an online program called Gizmos. Click the link below and scroll over the picture to launch the Gizmo.
https://www.explorelearning.com/index.cfm?
method=cResource.dspDetail&ResourceID=362
Instructions:
1. Drag the object off the shelf and place it on the scale and record the mass in g. 2. Then drag and drop it in the cylinder and record the volume (difference in water displaced). 3. Calculate the density (mass divided by volume).
4. Set the density of the fluid in the beaker to 1 g/ml (this is the density of pure water). Drop the object into the beaker to see if it sinks or floats.
5. If it sinks, move the density bar for the fluid until you can get the object to float.
Object
Mass (g)
Volume (ml)
Density (g/ml)
Float (Y/N)
Pink egg (#2)
11.1
9.7
1.14
n
Red egg (#11)
65.5
41.2
1.59
n
C
8
306
24.4
61.6
25.7
4.96
.96
N
y
After you complete this: your TA will call you back to discuss the findings.
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Part 2. Bathymetry and Plate Tectonics
In the power point you can compare the plate boundaries with the bathymetric (or physiographic) map to see how major features on the seafloor are related to plate boundaries. Physiographic map of the eastern Pacific and Atlantic
8. What features are found at divergent boundaries?
Rift valleys mid ocean ridge rift volcano
9. On the figure above use the insert/shape/line tool to draw the divergent boundary in the Atlantic. Make sure the line is red. [skip this if time does not permit]
10. Which bathymetric features are associated with convergent boundaries?
Deep ocean trenches, volcanoes, island arcs, submarine mountain ranges, and fault lines
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11. On the figure above use the insert/shape/line tool to draw the divergent boundary in the Atlantic. Make sure the line is red.
[skip this if time does not permit]
Part 3
Calculating Plate Rates For this section, you will use data from kmz files for the Dynamic Earth (dynamic_earth_kmz_file.v2.kmz) and Age of Ocean Floors (seafloor_age_5my_isochrons.kmz). 12. Looking at the key in the upper left hand corner, what is the time interval of the contours (in millions of years)?
0-270 million years ago 13. Where is the youngest ocean floor on the African plate?
Mid ocean ridges 14. What feature is this?
new ocean floor is created as the Earth's tectonic plates spread apart.
15. How old is the oldest ocean crust in the African plate in the southeast Atlantic Ocean?
180-200 million years old
16. Along the bottom of the profile (x-axis) are numbers in km, what are those telling us? That is the distance across the seafloor. 17. Why are
the values on the left side of the profile (y-axis) negative? It is going below sea level. 18. What do they represent? The shaded red curve is showing changes in elevation along our path.
19. What seafloor features can you identify from this profile?
Hint: Why is the elevation higher on the left (western side)?
And why does it slowly increase on the right (eastern side)?
And what are those peaks?
Now you will calculate the speed of plate movement for two different sections
20. What is the oldest age of the sea floor of the African plate?
280 million years old
21. How long is the path in km?
1027.44 km
22. What is the rate of movement of the African plate?
2.15 cm (0.85 in) per year.
23. Is it the same as the rate for the African plate in the South Atlantic (example)?
The African Plate moves at an average rate of about 2.5 centimeters per year.
24. What is the oldest age of the sea floor of the Eurasian plate?
280 million years old
25. How long is the path in km?
1027.445
26. Why did the path not go all the way to the land?
26. What is the rate of movement of the Eurasian plate?
7-14 millimeters per year
There are more examples for practice.