MAPPING THE OCEAN FLOOR
Background
For months, your ship, the HMS Aquatic, has been compiling data in an attempt to map parts of the ocean
floor. Your co-workers have been recording the time it takes for sound waves to return from the ocean
floor, after being sent out by your ship’s echo-sounding, SONAR, equipment. The chart below represents
the measurements taken as the ship moves away from the shore.
Problem 1
Your captain cannot figure out what to do with this data. He wants you to determine the depth of the
ocean floor that is represented by each signal’s travel time. Luckily for the captain, you know that the
speed of sound through water is 1463 m/s. You also know that to calculate depth, all you need to do is use
the formula: Depth = (time in seconds X speed (m/s)) / 2
It will be a piece of cake to complete the following table (the first 2 calculations have been done for you.)
Data Table: Determining the Depth of the Ocean Floor OECTA Teacher Resources Sub Task 4: Ocean F
Distance from Land
(km)
Time taken for
Signal to Return (s)
Speed of Sound in
Water (m/s)
Depth of Ocean Floor (m)
Depth (m) rounded
to the nearest 100
0 km
20 km
40 km
60 km
80 km
100 km
120 km
140 km
160 km
180 km
200 km
220 km
240 km
260 km
280 km
300 km
320 km
340 km
360 km
380 km
400 km
0s
0.2 s
2.5 s
2.7 s
2.9 s
5.0 s
3.1 s
3.2 s
1.2 s
2.3 s
2.5 s
0s
1.3 s
1.6 s
1.6 s
1.6 s
1.6 s
1.6 s
1.6 s
1.6 s
1.6 s
1463 m/s
1463 m/s
0 x 1463 / 2 = 0 m
0.2 x 1463 / 2 = 146.3 m
0m
100 m
To make it easier for the captain, graph your data. Graph the distance from shore on the x-axis, along the
top of the paper and the depth of the ocean on the y-axis, down the left side of your paper. Connect the
points by drawing a line with a ruler. Finally, color the area above the line in blue to represent ocean
water and below the line in brown to represent the ocean floor. Be sure to label both axis AND give the
graph a title.
Problem 2
You proudly show your captain your profile of the ocean. He asks what all the different peaks and lows
are supposed to mean, so you label the following onto your profile: continental shelf; continental slope;
trench; island; sea mount; and abyssal plain. Then write a description of each ocean form. Your
captain finally understands. Congratulations, you get a promotion.
* Activity adapted from Windspirit, 1994, and http://www.oecta.on.ca/curriculum/earth/grade8/8sgst4.pdf