Grade 7 - Ocean in Motion

Investigation 1: Where Did the Rubber Bath Toys Go?
(1 period)

How did rubber bath toys lost overboard in the Pacific travel to beaches many miles away?
In this 1-period investigation, students read a story about beachcombing for bath toys, and use a world map to record dates and locations where the toys were found. They begin to develop ideas about how the bath toys traveled.

Investigation 2: Weather and Circulation Systems
(5-day)

What causes surface ocean currents?
In this 5-day investigation, students develop an understanding that the large ocean circulations affecting Alaska mimic major weather patterns. They begin by creating and observing wave and riffle patterns and motion of objects in a tub. They plot possible current patterns on their map and organize meteorological data to determine how well wind patterns match their predictions. After a lecture/discussion to learn more about currents and weather patterns, they role-play shipping captains who must consider wind and current patterns to find the quickest route from Seattle to Anchorage. They finish up the investigation with a discussion that takes them back to the question of the toys’ movements.

Investigation 3: Waves and Tides
(7-10 day)

In this 7- to 10-day investigation, students develop an understanding of waves and tides and their motion through discussion, demonstration, and hands-on investigation. They demonstrate wave motion in containers, and create marigrams to show local tide data and to compare tide patterns from different parts of the world. They use their knowledge to consider whether waves or tides could account for the movement of the bath toys to their final locations.

What is a wave in the water?
In Activity 3A, Waves in the Water, students review and discover the parts and properties of waves through drawings and discussions, then create and observe waves in sealed jars and in a tub.

How are waves and tides related?
What are tides?
What causes the tides?
Activity 3B, Tides, uses a National Oceanic and Atmospheric Administration (NOAA) online tutorial to convey basic information about tides. Groups of students use graphic organizers to discuss and show the important ideas and facts that they know about tides.

What is the tidal pattern in a local or other Alaska bay? Why don’t the daily tides follow the 24-hour day of the earth? How do our tides compare with those in other locations?
In Activity 3C, Tide Patterns, students make a marigram graph using one month’s tide data for an appropriate Alaska body of water. A discussion of tides and their patterns follows the creation and examination of their graphs. They learn the difference between a diurnal, semidiurnal, and mixed semidiurnal tide, and then interpret unusual tides from different locations around the world.

Investigation 4: Temperature and Salinity Effects on Deep Ocean Currents
(7-9 days)

In this 7-9 day investigation, students are engaged in a variety of hands-on demonstrations and experiments that will help them understand thermohaline circulation in the ocean. They begin with an introductory activity that helps them to review or arrive at a definition of density, and then they demonstrate the effects of temperature and salinity on density and design an experiment to simulate ocean mixing. They experiment further with hot and cold water as they consider the effects of tropical and polar climates on ocean currents, and end by writing conclusions to summarize their learning.

How do the densities of fluids vary, and how does that affect their behavior?
In Activity 4A, Density, students watch a demonstration of layered fluids, then calculate densities of the fluids. They experiment to see how dissolved substances affect the density of fluids, and apply their knowledge by making predictions about new situations.

How do salinity and temperature affect ocean currents?
In Activity 4B, Hot and Salty, Cool and Fresh, students begin to discuss ocean currents. They experiment with mixing fresh water and salt water, and with mixing hot and cold water to observe currents, then design an experiment to test a new combination of fluids.

Do polar and tropical climates affect water temperature and ocean currents?
In Activity 4C, Currents in a Cup, students use colored water and cups in a tank to explore movements caused by the introduction of cold or hot water.

Investigation 5: Seafloor Topography
(3 - 4 days)

How does seafloor topography affect ocean current flow?
In this 3- to 4-day investigation, students will develop an understanding of the two basic ways seafloor topography influences ocean circulation patterns, steering ocean flows and providing barriers to deep water mixing. They draw and then construct a seafloor model and experiment with solutions of colored saline water, to see how they behave when the colored saline water encounters underwater barriers. They solidify their understanding through follow-up discussions and writing, and apply their understanding as they view an animated video clip illustrating interactions of ocean currents and climate.

Investigation 6: Debris Detectives Field Trip

How can we observe and measure movements in a local water body?
Students take a field trip to investigate some of the phenomena they have been studying. They inventory debris along a shoreline or riverbank and study local water movement patterns to develop ideas about where the debris might have come from.

Investigation 7: Global Conveyor Belt
(8 -12 day)

How do all of the pieces of the “ocean motion puzzle” fit together?
In this 8-12 day investigation students discuss and synthesize all of their experiences in the unit. With the help of an animation and a video, they develop a basic understanding of the global thermohaline “conveyor belt.” In small groups, they choose, complete, and present one of the following culminating projects:

• An examination of contamination patterns after the Exxon Valdez oil spill.
• An examination of garbage in the ocean and the subtropical gyre.
• Predictions of the contamination patterns from a hypothetical spill.
• An analysis of the effects of a hypothetical new landmass in the ocean.

As a class, students brainstorm and design an action project to apply their learning from the unit. Finally, students re-evaluate their answers to Investigation 1 using concepts and vocabulary from the entire unit to make sense of the story of the rubber bath toys.