1. Section 2 and 3 Ocean Waves and Tides
Chapter 11
The Oceans

2. Waves A Wave is the movement of energy through a body of water
In oceans, waves move through seawater.
Most waves form when winds blowing across the water’s surface transmit their energy to the water.

4. Waves Caused by: Wind Earthquakes
Gravitational force of the Moon and Sun.

5. Waves Caused by Wind
When wind blows across a body of water, friction causes the water to move along with the wind.
Wave Height depends on –
Strength of the wind
Length of time the wind blows
Distance over which the wind blows

9. Parts of a Wave Crest – highest point of a wave
Trough – lowest point of a wave
Wave Height – vertical distance between the crest and the trough
Wavelength – horizontal distance between two crests or two troughs
Frequency – the number of waves that pass a point in a certain amount of time

10. Wavelength
Crest
Wave Height
Still Water
Trough
Wave Parts

11. Wave Movement
When a wave breaks against the shore, the crest outruns the trough and the crest collapses.
Called a breaker.
In this case, water does move forward and backward.

12. Wave Movement
Waves slow down when they get close to shore because friction between the ocean floor and the water causes them to slow down.
When the bottom of the wave slows down, the tops keep moving forward until the waves topple over.

14. Wave Movement
When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward.

15. Tides The rise and fall in sea level is called a tide.
Caused by the interaction of the Earth, the moon, and the sun.
One low-tide/high-tide cycle takes about 12 hrs and 25 min.
Tidal range is the difference in ocean level between high-tide and low-tide

16. What is the Tidal Range? HT = 30 ft, LT = 20 ft HT = 20 ft, LT = 12 ft

17. Gravitational Effect of the Moon
Two big bulges of water form on the Earth: (tidal bulge)
one directly under the moon
another on the exact opposite side
As the Earth spins, the bulges follow the moon.

19. Gravitational Effect of the Sun
Spring Tides
Earth, Moon, and Sun are lined up
High Tides are higher and Low Tides are lower than normal
Occurs during a new moon or full moon

21. Gravitational Effect of the Sun
Neap Tides
Earth, Moon, and Sun form right angles
High Tides are lower and Low Tides are higher than normal
Occurs during 1st qtr. Moon or 3rd qtr. moon

23. Tides Q & A What are tides caused by?
Which exerts stronger gravitational pull on earth, the sun or the moon?
What happens when the moon faces one side of the earth?
What is a spring tide?
What position do the sun and moon have to be into create a spring tide?
Explain a neap tide.
In most places on earth, how often do high and low tides occur
How long does it take the moon to completely rotate around the earth

24. Complete the “Types of Tides” worksheet
The End