GLENDALE COMMUNITY COLLEGE 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: Glendale longitude: 34 12 N 118 15 W (a) Relative to Glendale, CA, which of the locations tabulated above is the farthest Latitude Longitude Sand Point, AK 55 2 N 16 3 W Honolulu, HI 21 18 N 157 5 W Tahiti, S. Pacific 17 37 S 149 27 W Shimazu, Japan 32 46 N 132 57 E (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 148 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) 2
Distance from Nova Scotia coast (km) 39 696 183 1238 147 186 2243 2398 263 2785 2862 317 343 379 4177 4564 4642 4874 One-way travel time for the depth soundings (seconds).61.89.49 2.373 2.719 2.571 2.82 2.324 2.76 1.186 1.483 2.126 2.868 3.115 3.362 2.917.99 Depth below the sea level surface (meters) Depth below the MSL (mean sea level), in meters 5 4 3 2 1 1 2 3 4 5 Distance from the Nova Scotia coast, in kilometers (c) Is the continental shelf wider off Canada or off France? (d) At what distance from Nova Scotia coast does this profile cross the Mid-Atlantic Ridge? Also show it on your profile..... (½ point) (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 5, 1, 15, 2, 25, 3, 35, 4 and 45 fathom bathymetric contours. (4 points) 3
(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) 4
Avalon San Pedro Depth below sea level (fathoms) 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) 4 2 2 4 Ma 4 2 2 4 Km 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
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 15 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 18 meters per second). (1 points) Show work. Give answer in meters.. X Ocean bottom.75 One-way travel time (seconds).5.25 Mio-Pliocene sediments 6
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) 7