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Lesson 5: Trench Measurement

The deepest ocean trench is called the Challenger Deep in the Mariana Ocean Trench located off the coast of Guam in the Pacific Ocean. The trench is almost 11,000 meters deep. The water pressure at this depth is about 1000 times as strong as the air pressure at sea level. Unfortunately, at certain depths it becomes difficult for gauges to give accurate information. Therefore, as scientists, we have to make predictions based on patterns and trends that we notice. Can you solve the problem of the broken depth gauge and determine the depth of the ocean trench in this simulation? Suit up and dive deep.

Doing the science

  1. Start the Trench Dive Simulation by clicking on the "Simulation" tab.
  2. Enter the Trench ID code in the space above Table 1.
  3. Click the blue “All” button to sample all variables at the surface. Record your data in Table 1.
  4. Using the green dive button on the left side of the screen, dive your submersible to about 1,000 meters.
  5. Repeat Step 3.
  6. Dive your submersible to about 2,000 meters and repeat Step 3.
  7. Dive your submersible to 2,980 meters and repeat Step 3. Please note that at a depth of 3,000 meters your depth gauge will break.
  8. Continue diving your submarine, collecting samples about every 500 meters, and recording data even when the submarine disappears. When all your data stops changing from one measurement to the next, your submarine has reached the bottom of the trench. Make sure to record your data in Table 1.

Table 1.

Depth (m)

0

1,000

2,000

2,980

---

---

---

---

---

Water Density (g/cm3)

Temperature (°C)

Pressure (N/cm2)

Salinity (psu)

 

Do You Understand?

  1. In the simulation, click on the blue “Graph” button. Next, click through each of the four variable buttons (Water Density, Temperature, Pressure, and Salinity) and review each graph. Describe the shape of each of the following graphs:

    a. water density

    b. temperature

    c. pressure

    d. salinity



  2. Which variable’s graph (water density, temperature, pressure, or salinity) is a continuous straight line?


  3. With the variable you identified in question 2, what is the relationship between that variable and depth?


  4. Determine the depth of the bottom of the trench based on the pattern you created in question #3 and enter it below.

    Trench depth = ___________ meters



  5. Describe how you determined the depth of the ocean trench.


  6. Why was the water density data not useful to you in predicting the depth of the ocean trench?


  7. Up to about what ocean depth could you use the water density data to predict the depth of the trench?


  8. Describe the relationship between temperature and ocean depth and provide a scientific reason for the shape of the graph of the temperature data.


  9. Provide a scientific reason for the shape of the graph of the pressure data.


  10. Describe the relationship between water density and ocean depth and provide a scientific reason for the shape of the graph of the water density data.