I need assistance with Part B on this midterm which i have attached below
Student Name Robert Trommer
Prof. Robert J. Sager
GEOLOGY 100 – MIDTERM EXAM (20% of course grade)
PART A: INTERPRETATON OF A STRATIGRAPHY CROSS-SECTION (10%)
Purpose: Apply the scientific method to interpret geologic data/information in this exercise. The student should review the topics
covered on rocks (igneous, sedimentary, and metamorphic rocks) and geologic time from your previous assignments, the online
textbook, course “Webliography” (Content tab), and online geologic research sources. Your research sources must be listed in
proper APA-style citations at the end of the questions.
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Figure 1.
Answer the following questions based on your interpretation of the geologic cross-section (Figure 1)
on Page 1.
1) How would you apply the “principle of original horizontality” to the layers (strata) in Fig. 1? Use the strata from B to M
(includes B-K-N-J-D-M). Explain.
The principle of original horizontality states that under gravity, sediment layers are always deposited horizontally. Therefore, the
layers in the figure being horizontal in nature must have been subjected to horizontal deposition.
According to the principle of original horizontality, the older beds lie under younger bed. Youngest formation exists above all the
beds. Oldest exists below all horizontal beds. Hence, youngest beds exist at top and oldest exists at bottom of horizontal beds.
From the statement, you have given that how to apply the principle of original horizontality to the beds B-K-N-J-D-M.
In that above rock sequence, the bed B lies above all the horizontal beds. Hence, it will be youngest of all the given rock beds.
K is older than B because it lies below the rock bed B.
N is older than K because it lies below the rock bed K.
J is older than N because it lies below the rock bed N.
D is older than J because it lies below the rock bed J.
M is the oldest bed of all the given beds in B-K-N-J-D-M, because it is existed at bottom of all horizontal beds
2) How would you apply the “principle of superposition” to the layers (strata) in Fig. 1? Use the strata from B to M
(includes B-K-N-J-D-M). Identify by letter the oldest strata and the youngest strata ? Explain.
The principle of superposition expresses that older rock is always overlaid by the younger rock. From the strata rock M is overlaid by
every other rock in the B,K,N,J,D,M strata and along these lines, rock M is the oldest, then D, J, N, K, and B being the youngest.
3) Which is the surface cover (identify by letter)? What would this be composed of? What are the possible sources of this surface
material? Why is this not considered part of the sedimentary rock strata? Explain.
The surface cover is letter F and would be composed if loose sediments called soil. Deposition is still present in this layer and it is not
bounded by strati-graphic columns.
4) What is a geologic “unconformity”? Are there any unconformities in this strata sequence? If so, what type of unconformity are
they? Describe in the stratigraphy (between letters) where at least two (2) unconformities are located, if any.
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Geologic Unconformity is discontinuity in rock sequence indicating interruption of sedimentation, commonly accompanied by erosion
of rocks below the break. The 2 types of nonconformities in the is a nonconformity between A and N and a disconformity below the
layer N and above the layer J
5) If rock region A is composed of igneous rock, would it be intrusive or extrusive igneous rock? What type of common igneous
rock would it most likely be composed of? What is this large igneous feature called?
It would be an intrusive igneous rock. The type of common igneous rock it would be composed of is granite. This large Igneous
feature would be called a Batholith
6) If the sedimentary strata from B to M had some metamorphic rock in it, which strata (identify by letter) would most likely have had
the most “contact” metamorphism with A? Explain.
D, N and K. The reason is that metamorphism occurs due to natural agencies, heat and pressure and affects the adjacent pre-existing
rocks.
APA citations:
PART B. SEISMIC PROFILE AND TECTONIC PLATE BOUNDARY EXERCISE (10%)
Purpose: Apply the scientific method to interpret geologic data/information in this exercise. The student should review
the topics covered on Plate Tectonics from your previous assignments, the online textbook, course “Webliography”
(Content tab), and other online geologic research sources that cover plate tectonics and earthquake distribution.
Your research sources must be listed in proper APA-style citations, including any websites you used.
Earthquake data has been collected over a 32-month period from a local seismograph network. A total of 2,476 seismic
events were recorded, you will be plotting and interpreting 30 of the earthquakes with the most reliable locations.
The master data set is provided in Table 2, shows only the earthquake foci locations that occur within the line of the
cross-section in Figure 1 at latitude 20ºS. The focus (pl. foci), or hypocenter, of an earthquake is the point of the
earthquake location below the surface. The epicenter is the point directly above the focus and located at the surface.
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Plot the earthquake data from Table 2 on the cross-section of Figure 2 by placing a dot on the cross-section at the
correct location for each earthquake focus. The x-axis is longitude, the y-axis is depth of the foci. (Note you may
scatter plot directly on the doc. cross-section or hand plot and copy, then attach to your exam.doc)
Longitude,
ºW
68
65
71
67
70
72
68
71
65
64
Depth
(km)
-18
-29
-15
-20
-12
-9
-23
-10
-27
-32
Longitude,
ºW
66
68
67
68
72
66
69
67
70
70
Depth
(km)
-24
-28
-21
-20
-6
-26
-20
-25
-14
-17
Longitude,
ºW
69
65
73
63
67
66
72
64
71
69
Depth
(km)
-15
-25
-8
-33
-23
-22
-12
-30
-9
-17
Table 2. Earthquake foci data recorded along the plane of the cross-section of Figure 2.
75ºW
3km
70ºW
65ºW
60ºW
Sea Level
Earth’s surface
-3km
-6km
-9km
-12km
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-15km
-18km
-21km
-24km
-27km
-30km
-33km
Figure 2: Cross-section along the 20ºS latitude (20S) parallel (X-axis=longitude, Y-axis=depth).
Interpret the data (Pages 3 and 4) by answering the following questions:
Answer the following questions based on your completed Figure 2 on Page 4.
1) Based on the pattern that emerged when you plotted the earthquake foci data (Figure 2) on Page 4, determine the
plate tectonic boundary type for this region. Indicate this by drawing a possible plate boundary (a trend line) on the
cross-section and show the direction of motion of each plate with arrows.
2) Describe the geologic processes and activity associated with this type of tectonic boundary.
3) Assess this region for geologic hazards. Name three geologic hazards that could be expected in this region.
a. Volcanic Eruption
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b. Tsunami
b. Earthquake
4) Where is this plate boundary location by latitude and longitude? Where is this plate boundary located in
geographic terms?
5) Which two tectonic plates (by name) form the plate boundary that is located there? (See Fig. 2). What major
geologic features will be formed there? Graphics may be used to support your answer.
APA Citations:
RjS 02/07/21
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