NAME______LAB DAY______
Ocean Contour Part 2 – The Pacific
Investigating the Deepest Ocean Depth - Mariana Trench
INTRODUCTION:
The deepest ocean depth is known as the Challenger Deep. It lies at the southern end of a major Pacific trench system known as the Mariana Trench, just south of the island of Guam (at 11O 22.394’ N and 142O 35.541’ E). The deep was named after the British research vessel, Challenger II, that first discovered it. In the 1960’s two scientists, Jacques Picard and Don Walsh, working with the US Navy, took the bathyscaphe Trieste to the bottom of the Challenger Deep, seven miles below the surface.
In this investigation we will use bathymetric data from the British Royal Navy charts of the Mariana Island group to create a side view or profile of the Challenger Deep. To accomplish this you will plot a simple line graph using the data below. Plot depth (in meters) on the y-axis and distance (in kilometers) on the x-axis. After you have drawn your profile, continue following the instructions which are found on the back of this investigation.
Distance (km) / Depth m(-)10 / -2200
(-)2 / -2000
(-).6 / -1280
0 / +406
.6 / -1280
16 / -1000
24 / -33
32 / -1000
40 / -3000
48 / -3915
56 / -4555
64 / -3000
72 / -2791
80 / -3000
88 / -2791
96 / -3658
104 / -3000
112 / -3200
120 / -2584
128 / -3100
136 / -4200
144 / -7100
152 / -8200
160 / -11200 (deepest/trench)
168 / -10000
176 / -9000
184 / -8000
192 / -7000
200 / -5900
208 / -5100
216 / -4588
224 / -4200
232 / -3840
240 / -3800
PROCEDURE
1. The graph paper was prepared by marking a suitable horizontal scale for distance from Guam, and a vertical scale for depths of the ocean. Note that it uses a horizontal scale of 1 inch = 30 km. The vertical scale is 1 inch = 3 km (3000 meters).
2. Plot all points shown in the table and label them as indicated in the footnotes of the table.
3. Note that all (Oceanic) Crust to the East (right) of the Challenger Deep is part of the Pacific Plate and all (Oceanic) Crust to the West (left) of the Challenger Deep is part of the Philippine Plate.
4. Shade all of the following:
Shade: / Color:“0” horizontal line / (Black) Thick Line (“Ocean Surface”)
Ocean (water) / Blue
(Land) Area(s) above the (sea) water level / Green (& Label Guam)
“Ocean Floor*” (Pacific Plate) / Dark Brown with ///lines (& plate name)
“Ocean Floor*” (Philippine Plate) / Light Brown (& plate name)
*Note: “Ocean Floor” = oceanic crust
5. a) What is the depth of the deepest part of the ocean floor shown on this graph?______m In km? ______km In miles? ______miles
b) How does this compare to the deepest part of the contour of the Atlantic that you drew in Part I of this lab?
6. Mark (w/ an “X”) the area(s) on your graph where the Philippine Plate meets the Pacific Plate. How many “meeting points” are there? ____What “Oceanic Feature” is shown here (i.e. what is the “Challenger Deep?”)
7. Observe a map showing the major lithospheric plates.
a) Where is the divergent plate boundary where new oceanic crust is being added to the Pacific Plate? (mark on graph)
b) On your graph, draw arrows to show the direction of motion of the Pacific Plate.
c) Where is the other end of the Philippine Plate located? (mark on graph)
d) On your graph, draw arrows to show the direction of motion of the Philippine Plate.
8. a) Based on the features that you see on the ocean floor, what tectonic process would take place within this section of the ocean floor (circle 1 below)? Why?
Subduction/Convergence - (“Ocean/Ocean” OR “Continent/Continent” OR “ Continent/Ocean”)
8. b) Note that the Pacific Plate is 9200 km wide, i.e. it’s 9,200 km from the Challenger Deep to the closest Continent’s “edge” in North America (near San Francisco, California). The Philippine Plate is 3600 km wide, i.e. it’s 3,600 km from Guam to the closest Continent’s “edge” in Asia (near Vietnam). Using these distances you can determine the “size” (in relation to each other) of these plates. Which plate do you think is larger? ______
What happens to the age of the rock as you move further from an area of seafloor spreading?
What happens to the density of rocks as it gets older and therefore has had more time to cool?
Based on these answers, which plate do you think will be heavier (and thus subduct under the other)? Why?
Note: Use (ß’s) to highlight this on your graph
Comparison of the Atlantic Ocean (Part 1) and Pacific Ocean (Part 2) Oceanic Contour:
1. Question #9 of Exercise 1 asked the following – “If you drew an ocean contour across the Pacific Ocean, extending from California to Japan, would you expect the profile to look the same?” Now that you have completed another contour (of the Pacific Ocean) for comparison, do the profiles look the same (use SPECIFIC EVIDENCE in your answer)?
2. Using the same analysis as in #6 (above), i.e. remembering that the total distance across the Pacific Ocean (from Vietnam to San Francisco) is almost 13,000 km (over 8100 miles!); you can compare the Pacific to the Atlantic Ocean. Look back at your graph from Part 1 of the exercise (the Atlantic Ocean). If it is (approximately) 4000 km from the Azores to Cape May, N.J.; and it’s (approximately) 1500 km from the Azores to Cape Roca, Portugal; how wide is the total distance across the Atlantic Ocean in km? ______In miles? ______(hint: to convert km to miles you divide by 1.6)
2b. Which ocean is larger? ______Do you think that this (size difference) contributes to the different Plate Tectonic events and resultant “Plate” movement?
3. Using Figure 4.6 (“Passive Margins”) for assistance – What type of Continental Margin is found along the Coast of Vietnam? ______(i.e. “Active” or “Passive”) What type of Continental Margin is found along the Coast of California? ______
Is this different than in the Atlantic (See Part 1)?
4. See question #5 (above) & compare your answer to Question #6 on Part 1 (Atlantic Ocean Exercise). Are the number of “meeting points” the same? ______Based upon your answer, what 2 tectonic activities are demonstrated (& where, i.e. in which Ocean, do you see these)?
NAME______Lab Day ______
CONTOUR OF THE OCEAN FLOOR – Part 1 – The Atlantic Ocean
Purpose: To draw a profile of the floor of the Atlantic Ocean along the parallel of 39oN, from Cape May, New Jersey to Cape Roca, Portugal.
Background: The accompanying table gives figures for depths of the Atlantic Ocean from Cape May to Cape Roca along the 39th parallel. Depths are found by soundings, usually with the echo sounder in deep waters and with a sounding line in shallow waters.
Distance from Cape May (km) / Depth (m)0 / (+) 1000 *1
161 / -200
201 / -1800
523 / -3700
765 / -4600
1047 / -5500
1449 / -5100
1811 / -5300
2093 / -5700
2294 / -5300
2375 / -3700
2576 / -2900
3059 / -4600
3220 / -3800
3462 / -3300
3542 / -2100
3582 / -1400 *2
3743 / -1300 *2
3945 / -1000 *2
3985 / (+) 398 *3
4065 / -1800
4347 / -3700
4508 / -5100
5072 / -4900
5313 / -4200
5474 / -1800
5514 / -900
5595 / -200
5635 / (+) 1991 *4
* Figures based on U.S. Navy Hydrographic Office Charts of Atlantic Ocean, editions of 1959-1960
*1. Label this point Cape May *3. Label this point Graciosa Island, Azores
*2. Label these points North Atlantic Ridge *4. Label this point Cape Roca
PROCEDURE
1. The graph paper was prepared by marking a suitable horizontal scale for distance from Cape May, and a vertical scale for depths of the ocean. Note that it uses a horizontal scale of 1 inch = 800 km. The vertical scale is 1 inch = 1600 m.
2. Plot all points shown in the table and label them as indicated in the footnotes of the table.
3. Note that all (Continental) Crust to the East (right) of the Mid-Atlantic Ridge is part of the Eurasian Plate and all (Continental) Crust to the West (left) of the Mid-Atlantic Ridge is part of the North American Plate.
4. Shade all of the following:
Shade: / Color:Ocean (water) / Blue
(Land) Area(s) above the (sea) water level
**Note: you can shade around & next to your graph area for this section / Green
Ocean Floor (North American Plate) / Brown
Ocean Floor (Eurasian Plate) / Brown with /// lines throughout
Using your (completed) graph, answer the following questions...
QUESTIONS
1. The continental shelf extends from the shoreline to a depth of about 150 meters. How deep is this in kilometers (1 km = 1000m)? ______
2. How wide is the continental shelf at Cape May? ______
at Cape Roca?______. Label both continental shelves (& the corresponding Shelf Breaks) on your graph.
3. a) Are continental shelves always the same width?
b) What factors do you think might account for differences in the widths of continental shelves? (see your text for help)
4. The continental slope extends steeply from the end of the shelf (@ the break) all the way to the ocean depths. Label the continental slopes and likely areas that these (the slopes) “meet” the deep ocean floor on both sides of the ocean. The name of these “meeting” areas (which are always changing) are termed the Continental Rise. Label where you think these areas are located on your graph.
5. The Continental Margin is comprised of 4 areas – The Continental Shelf, Shelf Break, Continental Slope and Continental Rise. Highlight these areas on your graph with a thick, black, line. What type of rock do you expect this area to be comprised of? Why?
6. The remaining area (i.e. that NOT highlighted by the thick, black, line) is considered (deep) Oceanic Crust. What type of rock do you expect to find here? ______
7. Highlight (w/ an “X”) the area(s) on your graph where these 2 areas meet (i.e. where Continental Crust meets Oceanic Crust). How many (meeting points) are there? ______Why?
8. a) Based on the features that you see on the ocean floor, what tectonic process would take place within this section of the ocean floor?
Seafloor spreading (Divergence) or Subduction
b) On the graph, label the place where this process would take place & explain what’s happening (and why):
9. The average depth of the world’s oceans is said to be about 3800 m (3.8 km). Does your graph show an average depth close to this figure?______
(hint: Compare the seafloor above 3800 m with the area below 3800 m)
If you answered “no”: What features do you think contribute to the average depth being shallower or deeper than 3800 m?
9. If you drew an ocean contour across the Pacific Ocean, extending from California to Japan, would you expect the profile to look the same? Explain why or why not.