Why Does the Ocean Rise and Fall

Introduction

Have you ever noticed that the water along the seashore is sometimes very high and, at other times, much lower? Where does the water go? Why does it return? Does the Moon really have something to do with it?

In this WebQuest, you will become an Ocean Tide Investigator. Your goal is to discover what causes ocean tides and how the positions of the Earth, Moon, and Sun influence high tide, low tide, spring tide, and neap tide.

Scientists explain that the Moon's gravitational pull is the main cause of Earth's tides, while the Sun also influences their strength. 

 

Task

Your group has been asked to prepare an educational presentation entitled “Why Does the Ocean Rise and Fall?”

By the end of the WebQuest, your group should be able to explain the causes of ocean tides and distinguish the different types of tides.

Your final product will be a 5–7 slide presentation or digital poster containing:

  1. A simple definition of ocean tides.
  2. An explanation of how the Moon affects tides.
  3. An explanation of how the Sun also affects tides.
  4. A diagram showing high tide and low tide.
  5. A comparison of spring tide and neap tide.
  6. At least three important facts about tides.
  7. A short explanation of why understanding tides is important to people.

Process

Step 1: Form your investigation team.
Work in groups of three to four students. Assign roles such as researcher, note-taker, designer, and presenter.

Step 2: Begin with the main question.
Discuss this question with your group:

“Why does the level of ocean water change throughout the day?”

Write down your initial ideas before doing your research.

Step 3: Investigate what causes tides.
Use the recommended resources below to study how the gravitational pull of the Moon affects Earth's oceans. NOAA explains that the Moon's tidal force produces ocean-water bulges associated with high tides as Earth rotates. 

While researching, answer these questions:

  • What is a tide?
  • What causes high tide?
  • What causes low tide?
  • Why does the Moon have a strong influence on ocean tides?
  • What role does the Sun play?

Step 4: Investigate spring and neap tides.
Study the positions of the Earth, Moon, and Sun.

During new and full moons, the Sun, Earth, and Moon are approximately aligned, producing a larger tidal range called a spring tide. When the Sun and Moon are approximately at right angles relative to Earth, their tidal effects partially offset each other, producing neap tides. 

Create a simple comparison:

Spring Tide:
Sun, Earth, and Moon are aligned → greater difference between high and low tide.

Neap Tide:
Sun and Moon are at right angles → smaller difference between high and low tide.

Step 5: Create your visual model.
Draw or digitally create a diagram showing the Earth, Moon, Sun, and tidal bulges. Label the following:

  • Earth
  • Moon
  • Sun
  • High tide
  • Low tide
  • Spring tide
  • Neap tide

Step 6: Connect the lesson to real life.
Research why knowledge of tides is important.

Think about:

  • fishing
  • boating
  • coastal communities
  • navigation
  • beach activities
  • flooding and coastal safety

NOAA notes that monitoring tides is important for understanding coastal conditions and how tides affect human activities. 

Step 7: Prepare your final presentation.
Combine your research, explanations, and diagrams into your 5–7 slide presentation or digital poster.

Each group member should participate in presenting the final product.

Evaluation

Your work will be graded using the following rubric:

Criteria Excellent – 20 Good – 15 Developing – 10 Needs Improvement – 5
Scientific Accuracy All explanations of tides are correct and complete. Mostly correct with minor errors. Some concepts are incomplete or unclear. Major concepts are incorrect or missing.
Research and Use of Resources Uses several reliable resources effectively. Uses appropriate resources with sufficient information. Uses limited resources. Little or no evidence of research.
Diagram and Visual Presentation Clear, accurate, well-labeled, and attractive. Mostly clear and appropriately labeled. Some labels or concepts are unclear. Diagram is missing or inaccurate.
Explanation and Organization Ideas are logical, clear, and easy to understand. Generally organized and understandable. Some ideas are poorly organized. Information is difficult to follow.
Group Participation and Presentation All members participate actively and explain confidently. Most members participate. Unequal participation is evident. Minimal collaboration or participation.

Total: 100 points

Conclusion

Through this WebQuest, you discovered that ocean tides are not random changes in sea level. They are strongly influenced by the gravitational relationship among the Earth, Moon, and Sun. You learned how high and low tides occur and why spring and neap tides have different tidal ranges.

More importantly, you used online resources to investigate a scientific question, analyze information, create a visual explanation, and work collaboratively with your classmates.

Before finishing, reflect on this question:

“How would our daily lives in coastal communities be different if we could not predict ocean tides?”