. What are continental margins? a. Same as plate margins; b. the drowned edge of
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Question
. What are continental margins?
a. Same as plate margins;
b. the drowned edge of continents;
c. areas where continental crust transitions to oceanic crust;
d. accreted terrains;
e. the drowned edge of continents where continental crust transitions to oceanic crust.
2. How many types of continental margins (NOT plate margins!!) are discussed in the textbook and
course notes?
a. Two types: passive and active margins.
b. Three types: passive, active and transform fault.
c. Four types: passive, divergent, convergent and transform fault.
d. Five types: passive, divergent, convergent, transform fault and hot spot.
3. In terms of topographic features, what is the difference between passive and active continental
margins?
a. Passive continental margins are tectonically stable, while active continental margins are characterized by
frequent, intense earthquakes and related episodes of mass wasting. Therefore, active continental margins
have a steeper slope and a wider rise.
b. Passive continental margins are wider than active ones.
c. Along active continental margins the slope merges with a trench and there is no continental rise, as the
majority of the material eroded from the continent is deposited in the deep trench.
d. Active continental margins border volcanic mountains; frequent eruptions deliver large amounts of volcanic
material that build a slope significantly steeper than along a passive margin.
4. Based on the information provided in the Main Concepts online, at what depth is the shelf break
(edge) usually found?
a. 50m;
b. 100m;
c. 130m;
d. 210m;
e. 250m.
ESSC 320 – Lab 3
2
B. CLASSIFYING CONTINENTAL MARGIN USING BATHYMETRIC PROFILES
For this part of the lab you will be using a series of bathymetric profiles (created with the program
GeoMapApp) to identify various features of continental margins.
The first margin is the west coast of Central America, which is shown in Figure 1.
5. Using the distance scale at the bottom of the profile, identify the location of the features listed in
Table 1 (on the figure). Not all of them are necessarily present. If they are not in your profile, write “not
present”. An example is provided at the end of this handout for a bathymetric profile along the coast of
South America. Notice that the location of the shoreline is indicated by a red arrow on each profile.
When you are done, find which answer below correctly lists the location of each feature in the profile.
Shoreline
(km)
Cont. shelf
(km)
Shelf break
(edge) (km)
Cont. slope
(km)
Cont. rise
(km)
Trench (km)
Ocean Floor
(km)
a.
210 210-130
130 130-120 120-90 90-40 40-0
b.
210 210-145
145 145-115 NP 115-40 40-0
c.
210 210-150
150-140 140-100 NP
100-40 40-0
d.
210 210-145
145 145-90 Np 90-40 40-0
NP = Not Present
6. What type of continental margin is this? Justify your answer.
a. Passive continental margin, because there is a trench.
b. Passive continental margin, because there is the continental rise.
c. Active continental margin because the shelf is narrow and the slope is wide with a low angle.
d. Active continental margin because there is a trench.
e. Transform fault continental margin because there is a transform fault.
The second continental margin is the northern coast of Alaska, which is shown in Figure 2.
7. Using the distance scale at the bottom of the profile, identify the location of the features listed in
Table 2 (on the figure). Not all of them are necessarily present. If they are not in your profile, write “not
present.” When you are done, find which answer below correctly lists the location of each feature in
the profile.
Shoreline
(km)
Cont. shelf
(km)
Shelf break
(edge) (km)
Cont. slope
(km)
Cont. rise
(km)
Trench (km)
Ocean Floor
(km)
a.
90 90-200
200
200-270 270-320 NP
320-460
b.
90 90-150
155
155-180 180-205 205-210 210-460
c.
90 90-180
180
180-220 220-300 NP
300-460
d.
90 90-167
167
167-180 180-270 NP
270-460
NP = Not Present
ESSC 320 – Lab 3
3
8. What type of continental margin is this? Justify your answer.
a. Passive continental margin, because there is a trench.
b. Passive continental margin, because there is the continental rise.
c. Active continental margin because the shelf is narrow and the slope is wide with a low angle.
d. Active continental margin because there is a trench.
e. Transform fault continental margin because there is a transform fault.
C. ESTIMATING THE AVERAGE WIDTH OF CONTIN
ENTAL SHELVES ALONG THE COAST OF NORTH
AMERICA (NAM)
Using several profiles along the coast of North Am
erica (NAM), you will find out the average width of its
continental shelves.
You will start with the west coast, and use 4 bathymetric profiles drawn at different latitudes (see the table
below). In each profile, the location of the shoreline (coast) is at 0 m water depth. In profiles where the land is
rather flat, the shoreline is indicated by a red arrow.
NAM WEST COAST
Profile
Start
End
A
134° 01’ W, 58° 20’N
138° 01’ W, 57° 02’ N
B
123° 50’ W, 44° 10’ N
127° 10’ W, 44° 11’ N
C
122° 47’ W, 38° 48’ N
124° 57’ W, 37° 45’ N
D
112° 30’ W, 26° 30’ N
114° 22’ W, 24° 45’ N
Using the distance scale at the bottom of the profiles in Figure 3, estimate the width of the continental
shelf in each profile and report the numbers in Table 3 below.
TABLE 3
West Coast Cont. shelf width
(km)
East Coast Cont. shelf width
(km)
Profile
A
Profile E
Profile B
Profile F
Profile C
Profile G
Profile D
Profile H
AVERAGE
AVERAGE
9. What is the average width of the continental shelf along the west coast of North America?
(If your
estimate does not match any of the numbers listed, approximate to the nearest one).
a. 500 km
b. 270 km
c. 180 km
d. 90 km
e. 40 km
f. 10 km
ESSC 320 – Lab 3
4
Next you will start investigating the east coast, and use 4 bathymetric profiles drawn at different latitudes
(Figure 4; see the table below for the exact location of the profiles). Notice how the edge of the continental
shelf at higher latitudes is at about 150-200m water depth.
NAM EAST COAST
Profile
Start
End
E
63° 24’ W, 57° 44’N
58° 15’ W, 58° 54’ N
F
53° 05’ W, 49° 12’ N 48° 15’ W, 50° 08’ N
G
62° 08’ W, 45° 12’ N 60° 20’ W, 42° 24’ N
H
75° 16’ W, 40° 02’ N 71° 30’ W, 38° 30’ N
Estimate the width of the continental shelf in each profile and report the numbers in Table 3 (above).
10. What is the average width of the continental shelf along the east coast of North America?
a. 500 km
b. 270 km
c. 180 km
d. 90 km
e. 50 km
f. 20 km
11. Why are the continental shelves bordering E and W North America different in width? Your answer
must be at least 100 words (not characters!) long.
Figure 5 show a bathymetric map and profile of
an area along the NAM east coast, between approximately
40°N and 46°N.
12. What is the name of the features found between the two yellow arrows? Using the bathymetric
profile, determine in which part of the continental margin they are located.
a. Deep sea canyons; they are located on the continental slope, some extend to the continental shelf.
b. Deep sea canyons; they extend from the continental rise to the deep ocean floor.
c. Deep sea fans; they are located on the continental rise.
d. Deep sea fans; they are located on the continental shelf and slope.
Explanation / Answer
1.e. the drowned edge of continents where continental crust transitions to oceanic crust.
2.c. Four types: passive, divergent, convergent and transform fault.
3. d. Active continental margins border volcanic mountains; frequent eruptions deliver large amounts of volcanic material that build a slope significantly steeper than along a passive margin.
4.130 meter
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