Plate Tectonics-Volcanic Arcs Lab Report_Feb6.2024
docx
keyboard_arrow_up
School
Clovis Commuity College *
*We aren’t endorsed by this school
Course
9
Subject
Geology
Date
Feb 20, 2024
Type
docx
Pages
5
Uploaded by CaptainFreedom8768
Geology
Name: Gurfateh Gill
Plate Tectonics and Volcanic Arcs Lab Report
Complete your responses in a color other than black or red
.
Part 1: Seismic Activity at Plate Boundaries
1
Geology
Name: Gurfateh Gill
Plate Tectonics and Volcanic Arcs Lab Report
1.
Based on the different colors of the earthquakes on the map above of South America (see legend at the bottom of map), can you see a different in earthquake depth as you go from west to east along the line (From A to B)? What about earthquake magnitude? What do you notice? As the earthquakes go more in depth they are around the same magnitude as the ones on the coast. However in the middle of A and B there isn’t anything.
2.
Use the data from the .csv filed linked on canvas to plot the cross-section
from A to B, either by hand or using a spreadsheet application like Microsoft Excel or Google Sheets.
Plot the location of the focus
of each earthquake (x = location east or west of the trench, y = depth) as a dot on the cross section below.
Plot the location of each volcano (x = location east or west of the trench, depth = 0 km) with a color or symbol different from the ones you used for the earthquakes.
-400
-200
0
200
400
600
800
1000
-700
-600
-500
-400
-300
-200
-100
0
100
Chart Title
eq depth
volcano
3.
In this location, the ocean plate to the west is subducting under the continental plate to the east. Comparing the diagram of a subduction zone below to the profile with 2
Earth-
quakes
in mantle
Geology
Name: Gurfateh Gill
Plate Tectonics and Volcanic Arcs Lab Report
earthquake locations that you just plotted, draw in the following features from the diagram onto your plot:
Label the trench
(zero on the x-axis) with an arrow pointing down and the word "trench".
Draw a line on the cross section to show the subducting plate
as it descends from the surface down into the earth.
Draw arrows on the subducting and overriding plates to show their movement directions
(on the diagram below, these are the fat gray arrows).
Circle the zone of melting
. At what depth (below the surface) and distance (horizontally, from the trench) does the magma that produces the volcanoes probably originate, and why?
The crust-mantle boundary (aka “Moho” or Mohorovicic discontinuity) is about 10 km deep under oceanic crust and 50 km deep under continental crust. Draw a straight horizontal line at the depth of the Moho below the oceanic crust
(from the left side of
the profile to the trench), and another at the depth of the Moho below the continental crust
(from the right side of the profile to the trench).
Label the part of your cross section where earthquakes are happening
in the mantle
(below the Moho). (this is not labeled in the example subduction zone diagram)
4.
What is the deepest earthquake plotted on your cross section? Do you think there is a lower limit below which earthquakes are not likely to occur? Explain your answer. (Hint: think about how rocks are different above and below the lithosphere-asthenosphere boundary). The deepest earthquake plotted is at 620km in depth and around 870km distance. Earthquakes occur in the crust or the upper mantle and so they are likely to occur in deeper depth.
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Geology
Name: Gurfateh Gill
Plate Tectonics and Volcanic Arcs Lab Report
Part 2: Plate Boundary Types 1.
The green, red, and blue highlighted plate boundaries are the ones at which magma is reaching the surface. What kind of plate boundaries do the different colors of highlighting
indicate? (For each color, circle the appropriate word from each set.)
o
Red: Divergent OR
Convergent OR Transform
| Continental OR Oceanic
o
Blue: Divergent OR Convergent
OR Transform
| Continental OR Oceanic
o
Green:
Divergent OR Convergent
OR Transform | Continental
OR Oceanic
2.
What kind of volcanic activity is happening at the red plate boundaries -- is
this spreading center volcanism
or arc volcanism
?
It is Arc Volcanism
3.
Magma is definitely reaching the surface in the blue
plate boundaries as well. Why are there so few red triangles (named volcanoes) along the blue plate boundaries? The reason
for having so few is because theyre deep in the ocean and only a few have hotspots which
create the volcanoes in the ocean.
Part 3: Subduction Zone Geometry
1.
How do the thickness
(vertical distance from surface to asthenosphere) and rock density
(heavy or light) of the overriding plate vary among the three different kinds of settings? o
Remember, the subducting plate is always oceanic crust; it's only the overriding plate that varies. Transform: Very dense crust, Divergent: Thin Crust which is less
dense, Convergent: Can be thick and thin it varies in size.
2.
Does the type of setting affect the angle of subduction
and the distance from the trench to
the volcano
? If so, what is its effect? It does and the affect is of the distance between the trench to arc and the density of it.
4
Geology
Name: Gurfateh Gill
Plate Tectonics and Volcanic Arcs Lab Report
3.
Does the type of setting affect trench depth
? If so, what is its effect? Yes, trenches in convergent settings are usually the deepest; in divergent settings, trenches vary in depth, and transform boundaries are usually shallow.
4.
Draw or describe the differences in subduction zone geometry between the three different
types of setting that could produce the differences in trench location and distance to the volcano that you described in questions 2 and 3. (If you draw diagrams, label the diagrams clearly.
) Make sure your answer makes it clear exactly how you think the difference in the type of overriding plate affects the shape of the subduction zone.
5
Small island large island continent