The Mediterranean Puzzle
Name_____________________________ Date__________ Period____
For thousands of years, sailors have used winds and ocean currents
to propel their ships. Ancient people spent much time speculating
about causes of winds and ocean currents, but it was left to modern
science to solve the puzzle of their origin. What causes these
currents in the ocean and atmosphere? Are they somehow related?
What role do these currents play in the global climate? These are
questions we will investigate in this lesson.
Let’s start with an ancient puzzle that was finally solved by Count
Luigi Marsili in 1679. Examine the map of the Mediterranean Sea.
The puzzle is this: Sailors had long known that swift currents flowed into the Mediterranean Sea from both the Black Sea and the Atlantic
Ocean. Many rivers and seas also empty into it. The Mediterranean has no apparent outlet; therefore, the water level should rise, but it does
not. Many explanations were offered – For example, the existence of hidden underground channels to drain the excess water. Can you solve
this puzzle? Count Marsili though he could, so he set up a model of the Mediterranean to test his ideas. In the following lab activities you will
trace the steps of Count Marsili as you discover the answer to the Mediterranean puzzle.
Lab #1 (demo) – View demonstration video and make observations
1. Make a diagram that records what you have observed. Use arrows to show current flow.
2. Could this demonstration serve as a model of the Mediterranean Sea? Explain.
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3. Using what you have learned, draw a diagram in the box of the Mediterranean showing the inflow and the outflow at both entrances,
Atlantic Ocean and Black Sea.
1. From your observations, which is saltier:
A. The Atlantic Ocean or the Mediterranean Sea?
B. The Black Sea or the Mediterranean Sea?
C. Which color solution represents the Atlantic Ocean?
D. Which salt solution represents the Mediterranean?
2. Why should the saltiness of the Mediterranean differ from the Atlantic? (Hint: Most of the Mediterranean basin has a warm and dry
climate) _____________________________________________________________________________________________
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3. Count Marsili thought that he could explain how the saltiness of ocean water could cause currents. To test his idea, he drew water
samples from different depths in the strait of Gibraltar, which connects the Mediterranean and the Atlantic Ocean. Using an equal
volume of each sample he found their masses and compared them with the mass of an equal volume of fresh water. What do you
think he found? _____________________________________________________________________________
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your prediction by doing Lab #2.
Lab #2 – Marsili’s Explanation
Part 1 – Comparing Masses
1. Determine the mass of the small beaker. __________g
2. Fill the beaker with 20 mL of the blue salt solution “Mediterranean,” get the mass of the salt solution and container. ________g
3. Subtract the mass of the container alone from the mass you got in step 2. The mass of the blue salt solution is ______g
4.
5.
6.
7.
8.
9.
Take another new small beaker and determine the mass. ________g
Fill the beaker with 20 mL of the clear salt solution “Atlantic, “get the mass of the salt solution and container. ________g
Subtract the mass of the container alone from the mass you got in step 5. The mass of the clear salt solution is ______g
Take another new small beaker and determine the mass. ________g
Fill the beaker with 20 mL of the red water, get the mass of the red water and container. ________g
Subtract the mass of the container alone from the mass you got in step 7. The mass of the clear salt solution is ______g
Analysis:
1. How does the mass of the “Mediterranean” solution compare with that of the “Atlantic” solution?
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How do both of these compare with the mass of the tap water? ___________________________________________________
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2. Divide the mass of each solution by its volume to determine the solutions density.
Solution
Mass (g)
Volume (mL)
Density (g/mL)
Blue “Mediterranean”
Clear “Atlantic”
Red Water
Part 2: Thinking About Density: Read the following questions about density and answer them in the areas provided.
1. What are the densities of the following materials?
Material
Mass (g)
Volume (mL)
Density (g/mL)
Water
30
30
Alcohol
21
30
Ice
27.6
30
Salt Water
33
30
Egg
31.5
30
a. Which of these materials would float on fresh water?__________________________________________________________
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b. Which of these materials would float on alcohol? _____________________________________________________________
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c. Which of these materials would float on salt water?___________________________________________________________
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2. Devise an experiment that would test your predictions? _____________________________________________________________
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Part 3: Layering Liquids: Fill each of the three test tubes ¾ full with the red, white, and blue solutions. Now use the technique shown below to
layer the three liquids in a test tube or drinking draw as directed by your teacher.
1. Can the layers be layered in any order? Explain. ______________________________________________
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2. List the way that the liquids layer themselves out, from top to bottom. ______________________________
3. How does this relate to Count Marsili’s explanation of the Mediterranean puzzle? ____________________
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