Alaska Sea Grant

Investigation 3 - Waves and Tides

Class Time Required

Activity3A: 2-3 class periods
Activity 3B: 1 class period
Activity 3C: 2-3 class periods 

Materials Needed
Teacher Preparation 1½ to 2 hours to read all of the materials, make copies, set up computer/projector, gather materials and set up/practice lab activities, find and print tide data. 
Prior Student Knowledge Students should have some experience with energy and energy transfer.
Vocabulary Amplitude, aphelion, apogee, crest, diurnal tides, ebb, flood, frequency, marigram, mixed semi-diurnal tides, neap tides, perigee, perihelion, semi-diurnal tides, spring tides, tidal current, tidal range, tide, trough, tsunami, vertical circle, wave, wave height, wavelength, wave period
Science GLEs Addressed

6th grade: SA1.1
7th grade: SA1.1, SB4.3
8th grade: SA1.1

Investigation 3Overview: In this 7-10 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.

Activity 3A: Waves in the Water

Focus Question: What is a wave in the water?

Engagement: (20-25 minutes)

Review the data on the student maps from Investigation 1. How long did it take for the toys to reach the shore after they were spilled? What might affect their speed and movement? Explain that in this activity they will be looking at one factor that helps to determine how an object moves from point A to point B on the ocean.

Ask the students: “What are the factors that affect how long it takes for the toys to reach the shore?” and have them write the question in their science notebook. Give the students two minutes to write their own answers, then have them share answers with a partner for two minutes. Each pair of partners can then join with another pair, forming a group of four to share and compile answers for two additional minutes. As a whole class, write a list of factors on the board as each group reports.

Factors that should come up are waves, wind, currents, tides, storms, and possibly others. Ask students to think about which factor is most important and explain why in their science notebook.

Exploration: (60-90 minutes)

Tell the students that they will be learning about waves. Assess prior knowledge as you develop a definition of “wave” through discussion, brainstorming, or another pair-sharing activity. Some definitions found in the dictionary:

A ridge or swell moving through or along the surface of a large body of water.

A disturbance traveling through water by which energy is transferred from one particle of water to another without causing any permanent displacement of the water itself.

A movement up and down or back and forth.

A disturbance, oscillation, or vibration, of water and moving through the water.

Ask for a volunteer to draw a wave on the board or overhead. Discuss, in general terms, the different parts of the wave that might be of interest as you study water motion. (For example “the top of the wave, the bottom of the wave, the distance from the top of the wave to the bottom, the distance from one high point to the next.)

Ask students to draw a wave in their science notebooks and to label its parts correctly. View a wave animation or project a diagram on the overhead projector for student use. Discuss the definitions of amplitude, wavelength, crest, trough, and equilibrium (still water or calm sea) level as they are labeling the parts of the wave. View the wave animation to see how energy moves through the water to create waves. Discuss the definitions of “period” and “frequency” and count the waves in the animation to find the period and frequency. If an online computer with a projector is not available, use a drawing on the board or overhead projector to talk through the concepts with the students. Ask students to add “period” and “frequency” to their wave diagrams and explain their meaning in their notebooks.

Water Wave Motion Lab (45-60 minutes)
Divide students into groups of 2-4 and make a copy of the student lab directions for each student to put in their science notebook. Adjust the lab directions as needed for the level of your students. For maximum inquiry, give fewer directions.

Prepare materials for the lab according to the teacher directions provided.

During the lab, check with each group, listening for their ideas and thoughts and guiding them past misconceptions.

Part 1A: Students make water waves in a sealed jar. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation in their science notebooks.

Part 1B: Students make water waves in a plastic tub, aquarium, or baking dish. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation. They compare Part 1A and Part1B as a group and design a graphic to show the comparison. At this point choose to have a large group share/discussion, writing the explanations from each group on the board/overhead, or do all three parts and then have a discussion.

Part 2: Students make waves and observe the motion of an object in and on the water. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation in their science notebook. After they finish Part 2, they are asked to think about this question: How does wave motion determine the time it takes for an object to move from point A to point B on the ocean?

Explanation: (10 minutes)

At the end of the lab, bring the class together for large group discussion of the questions “How does wave motion determine the time it takes for an object to move from point A to point B on the ocean?” The class should arrive at the conclusion that a wave is energy moving through the water, but the water particles only move in a circle. This means that an object on the water does not move because of the wave energy. Have students write the conclusion in their science notebooks.

Activity 3B: Tides

Focus Questions:
What are tides?
What causes the tides?
How are waves and tides related?

Engagement: (10 minutes)

Ask the students what they know about tides, and begin a KWL chart. Explain that you will be looking for the answers to these questions, as well as other questions they raise about tides:
How are waves and tides related? What are tides? What causes tides? What does wave energy have to do with tidal motion?

Exploration/Explanation: (45 minutes)

Project the NOAA Web Tide tutorial and work through it with students, providing guidance and discussing the concepts. Be sure to show the animation. (The reading level of the tutorial is high for most middle school students, so this may not work well as an independent assignment.)

If you do not have access to an online computer with a projector, use this pdf version of the Tide Tutorial.

Have students work in groups of 2-4 to discuss the important ideas, facts, and answers to the focus questions. They should work together to choose a format and create a graphic organizer that shows the important ideas, facts, and answers to the questions: What are tides? What causes the tides? How are waves and tides related? Each student should glue a copy of the graphic organizer into their science notebook.

Have groups share their graphic organizers, and complete the KWL chart about tides as a class. Students should add any ideas or facts they may have missed to their own organizer in their science notebook.

Important concepts listed should include the following:
•    Tides are regular and predictable.
•    Tides are very long-period waves that start in the ocean because of the forces of gravity from the sun and moon, and move toward coastlines.
•    Tides appear on coastlines as the regular rise and fall of the sea surface. Low tide on shore coincides with the wave trough, and high tide corresponds with the wave crest.
•    Incoming (flood) and outgoing (ebb) tides can create horizontal movement of water or currents. Tide currents can be strong in entrances, inlets, and narrow straits. They are weak in the open ocean.

Activity 3C: Tide Patterns

Focus Questions:
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?

Engagement: (15 minutes)

If you live on or near salt water, use information about your local bay or body of water for this investigation. If you are inland, make a class list of saltwater bodies in Alaska that students have visited, and choose one to be the focus of the investigation. Share stories and observations of tides.

Exploration: (45-90 minutes)

Students will graph local tide data, and then compare their graph to graphs of other periods of time for the same location.

Using overheads and/or student copies of the Marigram Information and Examples, introduce students to the idea of a marigram and show them how to make one.

Decide on the period of time for your graphs (one week, two weeks, one month), and divide students into small groups (2-4 students). Ask each group to plot the same week’s data, or assign specific weeks of a month or a specific month to each group, to cover a longer time period.
Distribute the following:

  • Local tide books, or printed tide tables for your area  along with moon phase data.
  • Copies of the blank graph or other graph paper. (The blank graph is for 7 days. To graph for a month on one page you will need to have graph paper with very small divisions lengthwise on the paper. 124 squares = 4 squares for each day times 31 days. A 2-week graph would need 56 divisions across the paper. Student graph paper could also be made on an overhead transparency to make it easy for them to share their work. These could be washed and re-used.
  • Student worksheet copied in a size that will fit in the student science notebooks (If you print at 80%, it will fit into the science notebook).
    Give students time with their group to answer the questions and construct their own marigram.

As groups finish their marigrams, give them the Tides and the Moon handout. They will read and answer a question about the moon’s influence on tides, and then add moon phases to their marigram and label the spring and neap tides. (Slower groups can finish this part as the class discusses it, or as homework).

Explanation: (15 minutes)

Bring the group back together as a class to discuss the marigrams. Share graphs with the whole class to get an understanding of the pattern that occurs over time. Discuss why it is important for people to know about tides. Give examples of people who use tide data. What makes the intertidal zone (between low and high tide) such a changeable and dangerous environment for the organisms that live there?

Use the tide diagrams to learn the difference between a diurnal, semidiurnal, and mixed semidiurnal tide. Identify the type of tide that was graphed in the previous activity.

Ask students to consider: Why do tides have different patterns in different parts of the world? Ask them to write their ideas in their science notebooks.

Look at the map of tide types. Ask the students to find other areas of the world that have tides similar to the ones you graphed. Identify different types of tides that can be found in Alaska.  Then, explain the following:

If the earth were a perfect sphere without large continents, all areas on the planet would experience two equally proportioned high and low tides every lunar day. The large continents on the planet, however, block the westward passage of the tidal bulges as the earth rotates. Unable to move freely around the globe, these tides establish complex patterns within each ocean basin that often differ greatly from tidal patterns of adjacent ocean basins or other regions of the same ocean basin (J.L. Sumich 1996).

Elaboration: (30-40 minutes)

Provide students with marigrams from tide patterns different from the ones they created earlier, using Four New Marigrams as a handout. Ask them to interpret the tides. The marigrams can be cut and glued into their science notebooks, and their interpretation of the tide and the answers to the following questions can be written next to them.

Ask students to answer the following in their science notebooks for each of the four marigrams:

  1. What is the amplitude of the tide? (It is the difference between high and low.) How does it differ from the Alaska tide that you graphed earlier?
  2. How many highs occur each day? How many lows? Is this a diurnal, semidiurnal, or mixed semidiurnal tide?
  3. In what other ways does this tide pattern compare with the one that you graphed previously? Do you notice anything else interesting about it?


  1. People often believe that there are no tides in the Mediterranean Sea because the tidal range (amplitude) is only a few centimeters. The tide in the north part of the Mediterranean is mixed semidiurnal, similar to that in Southeast Alaska and the Gulf of Alaska.
  2. The tide is said to be diurnal when only one high water and one low water occur during a tidal day. Tides along the Gulf Coast of Florida generally west of Apalachicola are of the diurnal type.
  3. Southampton, England, has a “double high tide” caused by the flow of water around a nearby island, the Isle of Wight. At Whitby, England, in the North Sea, the spring tide occurs two days behind the new/full moon. The reason for this is that the tide originates in the southern oceans, the only place on the globe where a circumventing wave (as caused by the tidal force of the moon) can travel unimpeded by land.
  4. The Bay of Fundy has the largest tidal range (amplitude) in the world.
Refer back to the map of tide types as needed (It might be helpful to print this map).

Evaluation: (35-50 minutes)

Discuss the question: “Could waves and/or tides account for the location/dates of toys that were found on beaches after the spill?

These questions may help to guide the discussion:
What are waves?
How do water particles move in waves?
How do objects move in waves?
What are tides?
How do water particles move in tides?
What is a tide current?
Where would you find weak tide currents?
Where would you find strong tide currents?
Do the currents always move in the same direction?
What do we know about tide currents in the locations where the toys ended up?
What would we need to know to find out?
Which is more likely to influence the movement of the toys, waves or tides?

Following discussion as a whole class or in small groups, have students decide which factor they think has a greater effect on the movement of floating objects. Ask them to write their prediction or idea and explain it in their science notebooks. Class sharing of these predictions can lead into the next investigation.

Teacher Preparation

Tips from Teachers

No tips are currently available.

Read through all of the investigation materials, directions, and background materials, and make decisions about instruction where appropriate. Print and copy handouts and overhead transparencies. Gather materials and practice lab activities for Activity 3A. View Web site and animations for Activity 3A and Activity 3B, and set up a projector. Find or make a copy of your local tide book for each group. Copy the Four New Marigrams handout for Activity 3C. If your school is inland, have students choose the water body to use on the day before you are going to do Activity 3C, so that you will have time to acquire tide data from the Internet and copy it. 

Curricular Connections

This investigation can provides connections to math through graphing activities and measurements and calculations of wave frequencies and periods. The many opportunities to write, discuss, and present information to the class provide connections to language arts.

Ideas for adapting to different local environment or context. Investigate local cultural traditions and knowledge related to tides. 

Materials Needed for Investigation 3:  

Student Handouts

Science notebooks

Student Lab directions (3A) Image

Marigram Information and Example (3C) (or make overhead transparencies) Image

Blank Graph (or substitute graph paper) (3C) Image

Student worksheet (3C) Image

Tides and Moon (3C) Image

Tide Diagrams (3C)

Four New Marigrams (3C) Image

Items for Group Display

Wave Diagram (3A)
World map or globe

Material Items

Lab materials, per group:

Glass jar (1 pint to 1 quart size) with tight-fitting lid

Mineral oil

Rubbing alcohol


Blue food coloring


Plastic tub, 5 gal aquarium,

baking dish



Fishing line

Metal washers


Ground pepper

Tide books or tide data from Internet

Facility/Equipment Requirements

Computer connected to Internet, with 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.*

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.*

The student demonstrates an understanding of motions, forces, their characteristics, relationships, and effects by
SB4.3 describing the characteristics of a wave (i.e., amplitude, wavelength, and frequency).

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.*

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.
Alaska Sea Grant University of Alaska Fairbanks Alaska Department of Education and Early Development NOAA