Name ……………………………………… /

Marks secured ……… /25

Test 1: Ocean –116 (Oceanography Lab.)

Dr. Poorna Pal

Note: Answer all questions/solve all problems, giving detailed answers, as may be needed.
Show all your work.

1.  Tabulated alongside are the latitudes and longitudes of selected locations on the Pacific Ocean region while the coordinates of Glendale, CA, are given below:
Glendale latitude: / 34°12’N
Glendale longitude: / 118°15’W
/ Latitude / Longitude
Sand Point, AK / 55°20’N / 160°30’W
Honolulu, HI / 21°18’N / 157°50’W
Tahiti, S. Pacific / 17°37’S / 149°27’W
Shimazu, Japan / 32°46’N / 132°57’E
(a)  Relative to Glendale, CA, which of the locations tabulated above is the farthest … / (2 points)
North? / ………………………… / East? / …………………………
South? / ………………………… / West? / …………………………
(b)  Use the longitude data tabulated above to compute the differences in local time between Glendale, CA, and the other locations and enter the results, to the nearest minutes (time), in the blank spaces below. / (3 points)
Show work.
Note that
15° longitude = 1 hour (time)
1° longitude = 4 minutes (time)
15’ longitude = 1 minute (time) / (i) / Longitude difference between Glendale, CA, and Sand Point, AK = / ……………………………………………………………………………………………………………………………………………………………………………………
\ Time difference between Glendale, CA, and Sand Point, AK = / ……………………………………………………………………………………………………………………………………………………
(ii) / Longitude difference between Glendale, CA, and Honolulu, HI = / ……………………………………………………………………………………………………………………………………………………
\ Time difference between Glendale, CA, and Honolulu, HI = / ……………………………………………………………………………………………………………………………………………………
(iii) / Longitude difference between Glendale, CA, and Tahiti, S. Pacific = / ……………………………………………………………………………………………………………………………………………………
\ Time difference between Glendale, CA, and Tahiti, S. Pacific = / ……………………………………………………………………………………………………………………………………………………
(c)  Use the coordinates tabulated above and plot all these locations (i.e., Sand Point, AK; Honolulu, HI; Tahiti, South Pacific; Shimazu, Japan; and Glendale, CA) on the map of the Pacific Ocean region below. / (2½ points)
2.  Tabulated below are the depth soundings data obtained across the North Atlantic along an East-West profile on 45°N latitude from the coast off Halifax, Nova Scotia, Canada, to that of Soulac, France.
(a)  Covert the one-way travel time data to depth values, using 1480 m/sec for the velocity of sound in water.
(2½ points)
(b)  Plot these data on the graph below, and construct the depth profile. / (2½ points)
Distance from Nova Scotia coast (km) / One-way travel time for the depth soundings (seconds) / Depth
below the sea level surface (meters)
0
309
696
1083
1238
1470
1860
2243
2398
2630
2785
2862
3017
3403
3790
4177
4564
4642
4874 / 0
0.061
0.089
0.049
2.373
2.719
2.571
2.820
2.324
2.076
1.186
1.483
2.126
2.868
3.115
3.362
2.917
0.099
0 / ………..
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(c)  Is the continental shelf wider off Canada or off France? / …….………………………………. / (½ point)
(d)  At what distance from Nova Scotia coast does this profile cross the Mid-Atlantic Ridge? Also show it on your profile.
/ …….………………………………. / (½ point)
(e)  Identify the abyssal sea floor on the profile that you have drawn above. / (½ point)
3.  The map of part of San Pedro channel shows depth soundings in fathoms.
(a)  Contour these depth values with 50, 100, 150, 200, 250, 300, 350, 400 and 450 fathom bathymetric contours. / (4 points)
(b)  Use this contour map to draw an ocean-depth profile from Avalon to San Pedro. (Note: Measure depth from the surface down on the graph). / (2 points)
Avalon / San Pedro
q / q

4.  The model interpretation of an observed magnetic anomaly over the Carlsberg Ridge, NW Indian Ocean, is shown below. Find the rate of seafloor spread here.

(1½ points)

Source: Chaubey, Bhattacharya, Murty and Desa, 1993, Spreading history of the Arabian Sea: some new constraints, Marine Geology, v.112, p.343-352.
Find the
spread rate.
Show work.
Give the answer in mm/yr
(1½ points) / …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
5.  The chart below is part of a seismic reflection profile across the outer continental shelf and slope off Mexico’s west coast.
(a)  What is the depth to the ocean bottom below point X (assume velocity of sound in water as 1500 meters per second). / (1 points)
Show work. Give answer in meters
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………………….………………………………………………………………………………………….………………………………………………………………………………………………………………………………………….
(b)  What is the thickness of the sediments below point X (assume velocity of sound in the sediments as 1800 meters per second). / (1 points)
Show work. Give answer in meters
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………………….………………………………………………………………………………………….……………………………

6.  A speedboat is running at 15 knots in the straight stretch of a canal and, along the parallel coastal road, a tractor is racing it at 25 km/hour. Which one is faster, the speedboat or the tractor? Find boat’s speed in km/hr and tractor’s speed in knots.

Notes: / 1 knot / = 1 nautical mile per hour / (1½ points)
1 nautical mile / = 1.15 statute miles
= 1.85 km
(a)  Which one is faster, speedboat or the tractor? / ……………………………………………….
(b)  Find the speedboat’s speed in kilometers per hour and the tractor’s speed in knots.
Speedboat / …………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
/ km/hr
(Show work)
Tractor / …………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
………………………………………………………………………………… / Knots
(Show work)

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