Introduction
Before introducing the concept of tides, students should understand the structure of the Earth and how it functions in the solar system.
Learning about the effects of gravity and inertia on the ocean students will establish an understanding of what causes tides.
Task
Students will learn:
- vocabulary associated with tides
- tides on Earth are caused by the gravitational pull of the Moon
- the features and movement of tides including what spring tides and neap tides are
- who is effected by tides
Process
Step 1. Go outdoors and explore and discuss the meaning of gravity and inertia.
Demonstrate the law of "what goes up must come down." Ask the students to throw a ball straight up into the air. Discuss with the students that the ball came down because gravity pulls objects down to the Earth.
Pair up the children and get them to swing each other around in a circle. The children will experience the feeling of gravity and inertia working.
Point out the moon or sun. Explain that gravity causes the Earth to rotate around the sun and the moon to rotate around the Earth.
Ask children lead in questions such as: Have you ever been to the beach? Did you find a perfect spot to put your blanket, only to see that a little later in the day, the ocean seems to be closer than it was before? And later still, if you don't move your blanket, you'll be in the water? What's happening? What do we mean when we say the tide is coming in or going out?
Step 2. Back in class, introduce the concept of tides by learning the following vocabulary: moon, earth, sun, gravity, inertia, ocean, tide, spring tide, neap tide, low tide, high tide.
Step 3. Ask students to brainstorm on what they think causes the tides.
•Why does the tide go in and out?
What are Spring tides and Neap tides?
Step 4: Discuss ideas about why it is important to know the tides.
Evaluation
Evaluate the students understanding of tides by answering the following questions:
a. Q. What are tides?
A. Tides are periodic rises and falls of large bodies of water. Tides are caused by the gravitational pull between the Earth and the Moon.
b. Q. How many times do we have Spring tides in a month? Why?
A. We have Spring tides twice a month. This happens when there is a full moon and new moon and the sun and moon are in line.
c. Q. Why does the sun not affect the tides as much as the moon does?
A. Because the sun is much further away than the moon.
d. Q. Why are storms more dangerous during a Spring tide?
A. Spring tides are higher than normal, and storms can raise the height of tides due to the increased rainfall and winds. This increased water level can cause flooding near coastal areas.
e. Q. List three groups of people who are interested in tides.
A. Recreational users e.g. surfers / Livelihoods e.g. fishermen / Scientists e.g.
studying the effects of tides
Conclusion
The gravitational pull of the moon creates two types of tides: high and low. A tidal bulge occurs in the oceans on the side of the earth nearest the moon; a second tidal bulge occurs on the far side of the earth. These bulges are high tides. The areas between the tidal bulges experience low tide. Usually two high and two low tides occur each 24 hours and 50 minutes.