ERTH 1050 Google Earth Hw 1
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School
University Of Connecticut *
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Course
1050
Subject
Geology
Date
Apr 3, 2024
Type
Pages
3
Uploaded by SuperSquirrelMaster627
Part 1
A.) Determine how far the point in Africa and the point in South America have moved apart (in km) due
to divergent plate motion (round to the nearest 1,000 km). (0.1 points)
5,275 km rounded is 5,000 km
B.) Take a screenshot of the path you created and add it to this document. (0.1 points)
2.) About how many millions of years ago (mya) were these points last adjacent? (0.1 points)
120 mya
3.) Using the largest number of the range for your answer to question 2 and using the distance measured
for your answer to question 1, calculate the average spreading rate for these points in km per million years
AND in cm per year. Explain how you calculated this rate in a sentence or two. (0.3 points)
Average spreading rate= distance (km) / time
5,000 / 120 = 41.67 km/mya
1 km = 100,000 cm
1 million years = 1,000,000 years
41.67 * 100,000 / 1,000,000 = 4.167 cm/year
Calculated this rate by taking the distance from question 1 and dividing it by time from question 2 due to
the formula and got the average spreading rate in km/mya. Then I converted it into cm/per year from the
conversions above.
4.) A.) Which spreading center is experiencing faster plate motion? How do the colored bands of the
seafloor age map help you determine this? (0.1 points)
The pacific is experiencing faster plate motion. The colored bands of the seafloor age map helps
determine this by showing the Altanitc being less wider and red than the Pacific meaning it is newer
seafloor spreading and has a slower rate.
B.) Based on the arrangement of active and passive margins surrounding the Mid-Atlantic Ridge and the
East Pacific Rise, what is different about the forces acting on the fast-spreading mid-ocean ridge
compared to the slower one? Write your answer in one or two complete sentences. (0.4 points)
At fast-spreading mid-ocean ridges they have a combination of ridge push force and slab pull force
whereas slower ones only have ridge push force.
Part 2
5 A.) In the image, on what side of the map is the subducting plate, and which side has the overriding
plate? (0.1 points)
The subducting plate is where the green convergent boundary is next to the problem 10 pin point. The
overriding plate is more to the left side where we see problem 10 pin point next to the volcano Feinga
Seamount.
B.) On which side of the trench is the Tongan volcanic arc? Ignoring the labels borders, how did you use
the pattern of bathymetry shown on the map tell you where the arc is? (0.1 points)
The Tonga volcanic arc is located on the left side of the subduction zone where problem 10 is located near
earthquakes and volcanoes. I just know trenches are formed at convergent boundaries so that’s how I
knew.
C.) You should also be able to see the velocity of plate convergence displayed here in mm/yr. Is it faster
or slower than the spreading rate you calculated in Part I? (0.1 points)
The velocity of the plate convergence is faster than the spreading rate I calculated in part 1.
6A.) What is the depth of the earthquakes directly beneath the volcanic arc associated with the Tonga
Trench? (0.1 points)
0-50 depth
B.) Assume that the earthquake depths define the Wadati-Benioff zone. Using what you know about the
Wadati-Benioff zone of earthquakes in a subduction zone, if you traveled to this depth directly beneath
the arc, what would you find? (0.3 points)
Since it is shallower, you would see initial stages of subduction and seismic activity which are associated
with high frequency of earthquakes.
C.) Use the ruler tool to measure the distance between the trench and the point on the arc represented by
the two Problem 10 placemarks (make sure you checked their boxes to make them appear). State this
distance in km and include a screenshot. (0.3 points)
191.13 km
7A.) What is the depth of the earthquakes directly beneath the volcanic arc associated with this
subduction zone? (0.1 points)
51-200 depth
B.) Use the ruler tool to measure the shortest distance between the trench and the point on the arc
represented by the two placemarkers labeled Problem 12. State this distance in km. You don’t need to
include a screenshot this time. (0.1 points)
297.22 km
8.) How do the earthquake depths beneath the volcanic arcs in these two locations compare? What does
this tell you about the relationship between the depth of the Wadati Benioff zone and the position of a
volcanic arc in a subduction zone? Write your response in one or two complete sentences. (0.4 points)
Since it is deeper in depth you will see the seismic activity but much steeper, increase in temperature and
pressure that could lead to the process of melting rock and generation of magma.
9.) Create a hand-drawn cross section illustration for each of these two subduction zones. You should use
textbook Figure 2.27a as a general guide, except your illustration can be two-dimensional. For each cross
section, do the following:
●
Orient them so that west on the left side, and east on the right. (0.1 points)
●
Use the arc-trench distances for each location to determine how steep or shallow to draw the
subducting plate (you can be approximate as long as the two subduction zones end up with
different angles of subduction). (0.3 points)
●
Draw appropriate thicknesses for lithospheric mantle and crust in both the subducting and
overriding plates. Keep in mind that oceanic and continental crust have different thicknesses!
Label these layers clearly. (0.4 points)
●
Draw and label the asthenosphere, the direction of convection in the asthenosphere, the trench,
the volcanic arc, and rising magma. (0.25 points)
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