Alaska Sea Grant

Investigation 5 - Seafloor Topography

Class Time Required 3-4 class periods
Materials Needed
  • Science notebooks
  • Ocean Features handout  PDF
  • Map of ocean floor topography 
  • Modeling clay
  • Rocks
  • Dishpans
  • One-liter bottles with straws attached
  • Water
  • Salt
  • Measuring tools
  • Water soluble food coloring
  • Pencil and erasers
  • 11” X 8.5” or 11” X 17’ white paper
Teacher Preparation About 2 hours to read, view internet sites and video clips, gather and print materials, set up and practice lab activity. 
Prior Student Knowledge Students will need prior experience with density, temperature and salinity currents. 
Vocabulary

Abyssal currents, Abyssal plains, Bathymetry, Contour Line, Continental shelf, Eddy, Mid-Atlantic Ridge (MAR), Mid-ocean ridge, Oceanic basin, Oceanic trenches, Seamount, Thermocline, Topographic Map, Topography, Volcanic arc


Science GLEs Addressed

6th Grade: SA1.1, SA1.2, SE2.1, SE2.2

7th Grade: SA1.1, SA1.2, SE2.2

8th Grade: SA1.1, SA1.2, SB1.1, SE2.1, SE2.2

Investigation 5Overview: In this 3-4 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 will draw and then construct a seafloor model and experiment with solutions of colored saline water to see how they behave when encountering underwater barriers. Students 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. 

Focus Question:

How does seafloor topography affect ocean current flow?


Engagement: (55 minutes)

Have the students think about how the wind flows around structures such as buildings, and natural structures such as mountains, hills, large rock structures, or clumps of trees or bushes. Ask the students which side of the building or natural barrier they would choose if seeking shelter from the wind. If they have spent time watching clouds, how did the clouds behave when they encountered mountains or barriers? Explain that fluids and gases (air is a gas) share similar behaviors in nature when they encounter barriers both natural and human-made.

Use an ocean floor map or Web site to show the students what the topography of the ocean floor looks like based on our current knowledge.
Global Seafloor Topography 

Global Seafloor Topography from Satellite Altimetry

An Interactive Global Map of Sea Floor Topography Based on Satellite Altimetry & Ship Depth Soundings

Distribute the Ocean Features handout. Tell students that under the ocean there are many topographical features that are similar to the topographical features that we see on continents. Point out and discuss various underwater topographical features  to help the students make connections with the vocabulary words and the features they are describing.

Briefly discuss the technology that was used to “see” these seafloor topographic features. A description of side scan and multibeam sonar will help students understand these concepts.

NOAA Office of Coast Survey Side Scan and Multibeam Sonar

NOAA Ocean Service Education movies of multibeam and side scan sonar show how the two types of sonar are used under water to “see” ocean floor features.

National Geophysical Data Center
has smaller sections of each geographical area of the ocean floor can be that can be downloaded. These can be printed or projected as a means of stimulating interest and generating questions in a large classroom, keeping everyone “on the same page” during discussion and question and answer sessions. If needed, review the concept of negative and positive numbers and how they are used when we talk about topography. The positive numbers are used to describe land that is above sea level. Sea level is the equivalent to the number 0 on the number line. Negative numbers are used to represent the depth of the ocean.

Also, discuss the measurements used on maps. In science the unit of measure is the meter. On the ocean the unit of measure used by fishermen is the fathom. One fathom is equal to six feet. Sometimes the unit of measure for fresh water is feet, and sometimes the depth of the ocean is given in feet. Make sure you consult your navigation chart (chart is the proper nautical term, maps refer to land) as to what the depth soundings are in fathoms, meters, or feet.


Exploration: (2 class periods, or 110 minutes)

Ask each student to design an original ocean floor topography on a blank sheet of paper. Their ocean floor should have two underwater barriers. The drawing provides a map that will be used to make a 3-D model of the design.

After they draw their “map,” ask each student to talk with another student, then in a group of four to explain to each other how they think denser and colder solutions will behave in their model. At this point you may choose to have students combine their efforts and create or choose one map per pair or group so they can work together to build a model. In their science notebooks, they should record in drawings and short narrations how they think the solutions will behave. This is also a good time to let students redesign their drawings of seafloor models if they think the drawings need improvement. It is easier to make corrections on paper than in the actual construction of the model! In the science world, scientists often consult each other and improve the design of tests before beginning to carry them out.

Look over the drawings, and ask the students for an oral explanation of how it will work. If needed, have the student make further adjustments and come back for approval. This quick assessment will allow you to determine the students’ depth of understanding of the ocean current flow. Once the students have completed their drawing and it has been approved, the student can begin the construction of their model. Make sure that the students record the changes they made, if any, in their science notebooks.

During the experiments, science notebooks are used to write a hypothesis as to how they think warm or cold saline solutions will flow in their seafloor model. They will also be required to write down their observations of what actually happened in the model. They can further reflect about why their hypothesis might be different from their observations.

Students will then construct their models with cleaned rocks and clay in a plastic storage container, following their design.

When the models are complete, fill the container with 50-60 degree F fresh water.

Student will run two experiments: one using the warm water bottle and one using the cold water bottle. They may decide which experiment they want to run first.

Demonstrate the procedure for students using a tub containing water only:

Choose one of the bottles that contains saline solution to match the average salinity of ocean water. Ocean water is about 3.5% salt. One has colored warm (110 degrees F) salt water to simulate the waters of the Mediterranean Sea, and the other has colored cold (32 degrees F) salt water to simulate ocean water found near the poles.

Gently lower the straw end of the bottle under the surface of the seafloor model at one end of the container. Stop just 1 cm above the bottom of the model, and then gently squeeze the bottle until most of the solution is out of the bottle. Be careful not to move the bottle, since that might create an artificial current.

While one student squeezes the plastic bottle, the other students in the group observe what is happening in the model. Observations should be recorded on their paper model, in their science notebook, or both. Observations are complete when the students see no further “action” in the model.

Then the “old” water can be gently removed (to not ruin the topographic model), the model carefully rinsed with clean fresh water until no more dye is present, and then refilled with clean fresh water. Rerun the experiment using the other bottle filled with the other solution. Don’t forget to have students record their observations on the second run of the experiment in their science notebook.


Explanation: (10 to 15 minutes)

As a class, discuss how the seafloor topography affected the water movement. Ask students to describe the ways in which their barriers changed the direction of the flow. Students should have observed that current flow is increased around steep objects or objects that confine the water flow to a narrow passage. This flow acceleration can cause large, slow-flowing water masses to become extremely strong and rapid currents.

Seafloor topography also provides barriers that prevent deep waters from mixing, except within deep passageways that connect ocean basins or in water-controlled overflow regions. Did anyone see an example of that in their model? Students will learn more about deep ocean currents in Investigation 7: Global Conveyor Belt. After discussion, ask students to respond to the prompt, “Explain by writing and/or drawing how seafloor topography affects deep ocean currents.”


Elaboration (10-15 minutes)

Watch the video animation showing how the ocean is related to climate in the tropical Pacific Ocean. Pay attention to the circulation patterns in the ocean as you watch.

Discuss some or all of the following questions:
How are the continents affecting the movement of water in the ocean?

What happens when the wind-generated surface currents hit Australia and Asia?

What happens when the deep, cold water runs into South America?

How would the climate be different if the continents were not “in the way”?

If there were a long, high mountain range rising from the seafloor, running north/south between the continents, how might that affect climate?

When the deep, cold currents moving toward South America encounter seamounts or islands, what happens to their speed and direction?


Evaluation:

Evaluation can take place in teacher monitoring and participating in the student group discussions at various times during the investigation. The periodic informal assessments with students can play a big part in correcting misunderstanding before it becomes a part of the student’s long-term memory

Final evaluations can include student writings and observations in their science notebook, student project completion, and students evaluating themselves on what went right and what went wrong in the investigation. Encourage students to think about what they could do to “fine-tune” their procedures. For example, maybe they should have taken more time to carefully squeeze the solution-filled bottles and to hold the bottle as still as possible to prevent artificially induced currents into the model.

Informal assessment also occurs when the teacher gives the quick assessment before the student starts building a seafloor model.

Use the student writing for evaluation of understanding. If desired, provide a word bank for students to use. Ask them to explain the two basic ways seafloor topography influences ocean circulation patterns.


Teacher Preparation:

Tips from Teachers

No tips are currently available.

Read all of the lesson and background materials and view the suggested Web sites to learn about seafloor topography and its effects on deep underwater currents. Practice the lab activity and experiment with the water temperature in the tub to find the temperature that gives the best results when either the warm (110 degrees F) salty water or the cold (32 degrees F) salty water is gently introduced. Prepare a 35 o/oo (parts per thousand) saline solution, add coloring, and fill bottles. Set up a temperature-regulated water bath for the filled bottles to control the temperatures of the warm and cold salty water. Print and copy Ocean Features handout.


Curricular Connections:


Ideas for adapting to different local environment or context:


Materials Needed for Investigation 5:  

Student Handouts
  •   Science notebooks
Items for Group Display

 Video Clip

Map of ocean floor topography (can be Internet projection)

Material Items
  • Ample amounts of modeling clay or other “barrier” like material (might be able to use cleaned rocks and build the clay around the rocks. In this case the rocks work as volume fillers, and therefore less clay would be used in the barrier construction; also, they wouldn’t float while immersed in water)
  • A dishpan or a 25 quart/24 liter low-profile plastic storage container
  • One-liter plastic bottles with a straw component to gently squeeze the water underneath the surface water just above the bottom of the seafloor model
  • Water
  • Salt
  • Measuring tools
  • Water soluble food coloring
  • Pencil and erasers
  • 11 x 8.5 or 11 x 17 inch white paper
Facility/Equipment Requirements 

Computer connected to the Internet and a projector.

Alaska Science Standards and Grade Level Expectations Addressed:

6th Grade:
The student demonstrates an understanding of the processes of science by

SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating.*
SA1.2 collaborating to design and conduct simple repeatable investigations. (L)

The student demonstrates an understanding that solving problems involves different ways of thinking by
SE2.1 identifying and designing a solution to a problem.
SE2.2 comparing the student’s work to the work of peers in order to identify multiple paths that can be used to investigate a question or problem. (L)

7th Grade:
The student demonstrates an understanding of the processes of science by
SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring and communicating.*
SA1.2 collaborating to design and conduct simple repeatable investigations, in order to record, analyze, interpret data, and present findings. (L)

The student demonstrates understanding of the structure and properties of matter by
SB1.1 using physical properties (i.e., density) to differentiate among and/or separate materials.

The student demonstrates an understanding that solving problems involves different ways of thinking by
SE2.2 comparing the student’s work to the work of peers in order to identify multiple paths that can be used to investigate a question or problem.* (L)


8th Grade:
The student demonstrates an understanding of the processes of science by
SA1.1 asking questions, predicting, observing, describing, measuring, classifying, making generalizations, inferring, and communicating.*
SA1.2 collaborating to design and conduct repeatable investigations, in order to record, analyze (i.e., range, mean, median, mode), interpret data, and present findings. (L)*

The student demonstrates an understanding of the structure and properties of matter by
SB1.1 using physical and chemical properties (i.e., density, boiling point, freezing point, conductivity, flammability) to differentiate among materials (i.e., elements, compounds, and mixtures).

The student demonstrates an understanding that solving problems involves different ways of thinking by
SE2.1 identifying, designing, testing, and revising solutions to a local problem.* (L)
SE2.2 comparing the student’s work to the work of peers in order to identify multiple paths that can be used to investigate and evaluate potential solutions to a question or problem. (L)
 

Essential Question:

  • What are the patterns of physical changes in aquatic environments?
  • How do they affect us?
  • What are the major weather and ocean circulation systems in Alaska?

Enduring Understandings:

  • Physical changes in the aquatic environment occur on a daily, seasonal, and long-term basis.
  • Weather systems and ocean systems have major influences on one another and the dynamics of matter and energy.
  • Science and technology can be used to detect and solve problems.
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