Section 2 and 3 Ocean Waves and Tides

1. Section 2 and 3Ocean 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 • HT = 50 ft, LT = 20 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