HOW OCEAN DEPTH IS MEASURED BY SOUNDING

Much of the oceans topography has been mapped by the use of devices such as sounding. In this method sound is sent from a ship's transmitter to the ocean's bottom at an angle. It bounces back to the ship at the same angle and is picked up by a receiver on the same ship. We know that the speed of sound is about 1534 meters per second (1534 m/s). By using this information and applying the following formula, ocean depth can be measured and mapped.

The formula for measuring ocean depth:

## D = 1/2 T x V

D = depth

T = time

V = speed or velocity of sound in water (1534 meters per second)

Using this formula, find the depths of the ocean in the given locations and plot the depths on the graph top make a topographical map.

In a certain area of the ocean, a ship traveling in a straight line receives the following sonar signals:

Location A. 1st signal...........1 second

Location B. 2nd signal...........2 seconds

Location C. 3rd signal...........4 seconds

Location D. 4th signal...........8 seconds

Location E. 5th signal...........6 seconds

Location F. 6th signal...........4 seconds

Location G. 7th signal...........2 seconds

Location H. 8th signal...........2 seconds

Location I. 9th signal...........2 seconds

Location J. 10th signal...........1 second

Find the depth at each location.

A_______________ B_____________ C__________________

D_______________ E_____________ F__________________

G_______________ H_____________ I________________ J____________

Use the supplied graph and draw a map of this part of the ocean's floor (topography)

## Making and Ocean Profile

Imagine you are the sonar crew working with the world famous oceanographer, Captain Jacques Yves Cousteau of the sailing ship Calypso. Your scientific mission is to chart the Atlantic sea floor along 39°N latitude. You set sail from Atlantic City, New Jersey and traverse the mighty ocean to your destination in Lisbon, Portugal. Along the way, you use your sophisticated sonar to probe the unseen depths below. You collect a wealth of data on the depth of the ocean floor, which is in the table on the next page. Now, you will use that data to create a graph and profile of the ocean bottom. Good luck, and may the seas be kind to you...

Take time to make sure that your graph paper is properly set up. A well-designed graph includes the following:

1.        A title that identifies your data

2. An x-axis and a y-axis

3. Axis labels including metric units

4. Well-chosen number scales along each axis

Here are some questions to help design your graph:

1. What data and label go along the x-axis?

2. What data and label go along the y-axis?

3. If we are plotting depth below the ocean surface, where should we put zero on the y-axis?

Plot each point in the data table on your graph. Once all of the points are plotted, connect the points with straight lines. This will give you a profile of the changing depth of the ocean as you travel along 39°N latitude in the Atlantic Ocean from west to east.

Research ocean floor features in your textbook, in the library, on the Internet, or from your class notes. On your graph, identify and label the following features: Continent, Continental Shelf, Continental Slope, Abyssal Plain, Mid-Ocean Ridge, Island, and Seamount. Note that this traverse does not cross any Trenches.

1. What ocean floor structure occurs between 0 and 160 km east of New Jersey?______________

2. What ocean floor structure occurs between 160 and 1050 km east of New Jersey?______

3. What ocean floor structure occurs between 1000 and 2000 km east of New Jersey?_____

4. What ocean floor structure occurs between 2000 and 3000 km east of New Jersey?_____

5. What is the scale of your x-axis? 1 unit =

6. What is the scale of your y-axis? 1 unit =

7. If you wanted to draw your profile to scale, the units and distances along both your x-axis and y-axis would have to be the same. Your profile as it is drawn now is exaggerated. To find the vertical exaggeration, divide your x-axis by your y-axis.

What is the exaggeration?_________________________________________________

8. If you drew your profile to scale, about how long a sheet of paper would you need?_________

 Atlantic Ocean Profile Data along 39°N Latitude Sonar Reading Distance from New Jersey (km) Depth to Ocean Floor (m) 1 0 0 2 160 165 3 200 1800 4 500 3500 5 800 4600 6 1050 5450 7 1450 5100 8 1800 5300 9 2000 5600 10 2300 4750 11 2400 3500 12 2600 3100 13 3000 4300 14 3200 3900 15 3450 3400 16 3550 2100 17 3600 1330 18 3700 1275 19 3950 1000 20 4000 0 21 4100 1800 22 4350 3650 23 4500 5100 24 5000 5000 25 5300 4200 26 5450 1800 27 5500 920 28 5600 180 29 5650 75 30 5700 0

Fill in the Blank    Name:______________________________           Class:  Date:

Fill in the blanks in these sentences with the word that fits.

1.  _____________      is a sediment deposited by currents with the large rocks at the bottom and the fine material at the top.

2. Land deposits found in the deep sea are called______________________________________

3. The continental________________is a zone subdivided into shelf, slope, and rise.

4. The sinking of a broad area of crust without much change is___________________________

5. A unit of__________           equal to about 6 feet is fathom.

6. A trench is a narrow,________, ocean valley.

7 _____ _________ooze is produced from the accumulation of diatoms on the sea floor.

8. Soundings are depth____________ of the ocean basin.

9. Gently sloping zone bordering a continent is the  ____________shelf.

10. The rounded, layered lumps found on the ocean floor; contains 20%  _______with some iron, nickel, and copper.________________

11. A flat topped, submerged seamount is a        ______________

12. The steep_______________angle from the shelf break to the abyssal plain.

13. A device that plunges a hollow tube into bottom sediments to remove a verticle sample is a ______________

14. A___________________volcanic peak of more than 1000m is a seamount.

15. An island arc is a chain of islands formed where plates_______________________

16.        _________________  are hills of less than 1000m found on the abyssal plain.

17. A transform fault that is___________________    to a ridge or rise.

18. The flat ocean floor is the_____________________________

19.___________ is the transport of sediments such as rocks, sand, and gravel from land matter out to sea by wind, water, and ice.

20. The rise is a gentle slope formed by the_____________________ of sediments at the base of the slope.