1. Waves and Tides Section 2.1

2. Do Now-Check Homework Check & Reflect (p. 346)
You should not drink water from a stream even if you know it’s not contaminated by human activities. It may have naturally occurring organisms that are harmful.
Water supplies come from melting water or rainwater depending on the season. The amount of silt and contaminants in water may vary with the amount of flow in the stream. For example, after severe storms, the flow may increase and water may be contaminated, or in the spring melted water can bring large amounts of organic material from rotting leaves that had trapped ice.

3. AYL Answers (p. 347)
1. Potable water is water that is safe to drink. Out of a sample of 1000L representing the world’s water supply of fresh water, only L is potable.
3. Chlorine is added to our water supplies to kill organisms that might make people sick, such as bacteria or protozoa.
4. Water is described as being ‘hard’ when it contains dissolved calcium and magnesium. Soft water is water that has little calcium and magnesium.

4. The Plan
Discuss waves.
Demo of the movement of waves.
Causes of waves.
Effects on shorelines.
Tides and their causes.
I can describe the source and motion of waves and tides.

5. Wave Experiences

6. Waves and Tides Waves and tides are two ways in which water moves.
1. Waves are movements on the surface of all bodies of water, including small puddles. .
2. Tides are regular rising and falling of very large bodies of water.
Tides also happen in lakes and rivers, but they are so small we cannot see them.

7. Making Waves (p. 350)

8. Demo-The Movement of Waves
waves transmit energy but not matter. c

9. Waves

10. The Movement of Water Waves
Recall that waves are a form of energy.
Waves begin from a disturbance.
Waves are changes in patterns that move along the water’s surface. The water itself does not move very far, but waves can move over long distances.

11. Parts of a Wave

12. The Causes of Water Waves
Most waves are caused by the combination of:
1) A local sea and 2) swells.
Local seas are made by the wind:
Wind speed increases.
Fetch is the distance the wind blows over the water.
Time the wind has blown over fetch.

13. The Causes of Water Waves
Swells move away from local seas (where they were produced) and continue without wind.
In the open water the waves appear to move up and down.

14. Why do Water Waves Buckle and Crash?
When the wave reaches the shore it drags on the bottom of the ocean and slows down, which causes the top of the wave to rise up and crash down on the shore; this causes the most damage.

15. Effects of Waves on Shorelines
The force of waves can affect both a hard rock and soft sand shoreline.
Waves regularly cause erosion on land surfaces.

16. How Waves Change Shorelines

17. How Beaches are Formed
The type of rock that the shoreline is made of will if it will have a sandy beach or not.
Rock fragments eroded along the shore rub against each other and get polished and smoothed into tiny pebbles or grains of sand.
Waves are changing the shores
constantly.
Sea caves and arches can be formed
by the action of waves eroding rock
along the shore.

18. What nice beaches have you been to?

19. Prince Edward Island

20. Tsunamis They are very large waves.
Caused by undersea earthquakes, seabed slides, or large volcanic eruptions.
They occur ~every 5-15 years, but have no definite pattern and cannot be predicted.
Tsunamis means ‘harbor wave.’

21. What is a Rip Tide?

22. Tides Tides are daily changes in the water level of the oceans.
Tidal changes are seen regularly along the coast.
Most places there are two high tides and two low tides a day.

23. Tides High tide is the highest water level along the coast.
Low tide is the lowest water level along the coast.

24. Largest Tides in the World
The Bay of Fundy has the largest tides in the world!

25. The Causes of Tides
Water is affected by forces in space because of centripetal force.
The main cause of tides is the gravitational force of the moon.
The sun also has a small influence.

26. The Causes of Tides
The side closest to the moon feels a strong pull from the moon creating a bulge.
The opposite side of the Earth also has a smaller bulge due to other forces.
The bulges on both sides are the high tides.
As the Earth rotates the points of the high tides also change.

27. Tide Times
The movements create 2 high tides and 2 low tides every 24 hours and 50 minutes (called the lunar day).
Very similar to the 24 hour day (solar day).
People keep track of the tides with guides called tide tables.

28. Homework
Check and Reflect (p. 354) #1, 2, 4.