Driving Currents
Part One from: http://education.arm.gov/lessons/waves.html
Part Two inspired by: http://oceanworld.tamu.edu/educators/currents/activities/CURR_systems.htm
Part Three from: http://www.lessonplanspage.com/ScienceOceanCurrents78.htm
Modified by: Kirstin Bittel
Time: / 3 Class periodsPreparation Time: / 10-15 minutes making copies
Materials: / Overhead of World Ocean Current Map available at http://www.physicalgeography.net/fundamentals/8q_1.html (best if in color)
For Part One…
Beach sand
Baking Dishes
Fans or hair dryers
Tap water
Rulers
For Part Two…
Ice cubes (colored blue)
Hot water (colored red)
Clear baking dishes (one per group)
Straws
For Part Three…’
Beakers – 6 per group
Salt
Water
Food coloring – 5 colors (to differentiate salinity)
Scale to measure salt
Abstract
Students will conduct a variety of investigations to see how water, heat, and salinity affect the flow of the world’s ocean currents. This lesson draws upon information that students developed in the previous lesson, Message in a Bottle.
Purpose – Exploration of the many factors that affect the flow of the world’s ocean currents.
Objectives
Students will be able to:
Describe in discussion of an exploration:
1. how wind currents affect surface ocean currents
2. how temperature affects ocean currents
3. how salinity affects deep ocean currents.
4. how temperature and salinity affect density.
National Science Education Standard:
CONTENT STANDARD D: Earth and Space Science
ENERGY IN THE EARTH SYSTEM
· Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth’s original formation.
· Heating of earth’s surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents.
· Global climate is determined by energy transfer from the sun at and near the earth’s surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth’s rotation, and static conditions such as the position of mountain ranges and oceans.
GEOCHEMICAL CYCLES
· Movement of matter between reservoirs is driven by the earth’s internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of the matter. Carbon, for example, occurs in carbonate rocks such as limestone, in the atmosphere as carbon dioxide gas, in water as dissolved carbon dioxide, and in all organisms as complex molecules that control the chemistry of life.
Teacher Background
The world’s ocean currents are driven by many forces. The water in the upper ocean is driven primarily by the wind. Deep ocean currents are driven by salinity and temperature (both of which affect density). The salinity of water is related to the geologic formations in an area. Salinity tends to be lower near igneous formations and higher near sedimentary formations.
Surface currents tend to move relatively quickly (warm waters more so than cold waters), while subsurface currents flow more slowly.
Related and Resource Websites
Ocean World - Currents
http://oceanworld.tamu.edu/students/currents/index.html
Surface and Subsurface Ocean Currents
http://www.physicalgeography.net/fundamentals/8q.html
Ocean Current Temperatures
http://geography.about.com/library/misc/blcurrents.htm
Activity
Part One - Wind
1. In yesterday’s lesson the students mapped “Message in a Bottle” to describe ocean currents. They will use that information in today’s lesson. Remind students that yesterday they used bottles floating on the ocean to discover ocean currents. Reveal the ocean current map to students.
2. Have students compare their maps they created yesterday on the overhead. What is similar? What is different?
3. Ask students to look carefully at the surface currents map. Draw their attention to the oceans. Is there a boundary where one ocean starts and another stops?
4. Ask students, “Since the world really has one large ocean, what might cause the water to move in the fashion it does with some surface currents flowing to the equator and others away from the equator?”
5. Explain to the students that they are going to explore some of the different factors that affect ocean currents. Divide the class into groups and have the groups do the following:
i.) In a baking dish place the sand to construct a beach at one end.
ii.)Fill the baking dish with water to a depth of about 5 centimeters.
iii) Place the fan or hair dryer on one side of the container so that the fan can blow onto the surface of the water. It should be aimed down the tank along the surface of the water at about a 45-degree angle. Switch on the fan (or hair dryer). Allow 2 minutes for each trial. Let the students observe the results.
6. Select a few students to share their results with the class.
7. When students have finished sharing, ask them to repeat the above experiment by changing one variable. Examples might be force of the wind, angle, water depth, water temp, etc. Again they should collect data and share their results with the class before the end of the period.
8. At the end of class ask students to describe how wind affects surface ocean currents.
Part Two - Temperature
1. Ask students to think about the primary source of energy for our planet, the sun. Where are the sun’s rays most concentrated? [equator] How does that concentration of solar radiation affect the oceans? [heats them] Where do they think the oceans are coldest? [polar regions] What evidence supports this belief? [presence of icebergs and glaciers]
2. Divide the class into groups and send them to their laboratory stations.
3. Groups should complete the following while at their laboratory stations:
1) Fill a clear baking dish with warm/hot water colored red to represent the warm water near the equator.
2) Place one or two blue ice cubes at each end of the baking dish, representing the cold water near the poles.
3) Invite them to predict what will happen as the ice cubes melt.
4) Students will observe the results. (The cold water will sink and move along the bottom of the baking dish toward the warmer water in the middle. The warmer water will move toward the ends of the baking dish; as the cold water begins to warm, it will begin to rise.) 5) Have students use a straw to simulate wind currents. How does this affect the flow of the hot and cold water?
6) Students should record the results of their experiments, accompanying their reports with labeled diagrams and an explanation of how differences in water temperature in different parts of the “World Ocean” cause ocean currents.
4. When the groups have finished, invite them to share the results. What did they observe? How do hot and cold water move to create currents? How does wind play a role in those currents? How does temperature affect the density of the water? [Colder water is denser so it sinks; warmer water is less dense so it floats.]
Part Three – Salinity
1. Ask students, “When you think about oceans and lakes, what quality of ocean water makes it so distinguishable from lake or river water? [salinity]
2. Tell students that different parts of the ocean are saltier than others. Ocean regions near igneous formations are less salty, while ocean regions near sedimentary formations are saltier. How do you think the amount of salt affects density? Do you think that will affect the way ocean currents flow?
3. Divide students into groups and send them to their laboratory stations.
4. Have groups create 5 different concentrations of salt water using the directions below. Students should add 2 drops of food coloring to each solution so that the differentiating salinity can be distinguished later on.
5. Have students put 100 mL of water in each beaker. In beaker one they should place 2 drops of red coloring and 5 grams of salt. Beaker two should be colored yellow with 40 grams of salt in it. Beaker three should be colored green and contain 80 grams of salt. Beaker four should be colored blue and contain 140 grams of salt. Beaker five should be colored purple (one red drop and one blue drop) and contain 220 grams of salt.
6. Have groups tilt their 6th beaker and slowly and carefully pour the solutions into the beaker. They should pour the purple solution, then the blue, then the green, then the yellow, and finally the red. Students should carefully record their results.
7. What do they notice? What happens to the layers? Do they mix?
8. As a class, determine how salinity might affect ocean currents.
Closure
How else might we work to determine the way the oceans move and why? What characteristics of ocean water might affect its currents?
Embedded Assessment
As the students discuss their explorations are they able to explain that winds tend to move the surface currents in the same direction they are flowing? Do they explain how salinity and temperature affect deep ocean currents? Can they explain how temperature and salinity affect density?