Section 2 and 3 Ocean Waves and Tides

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Section 2 and 3Ocean Waves and Tides

• Chapter 11
• The Oceans

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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
  waters surface transmit their energy to the
  water.

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Waves

• Caused by
• Wind
• Earthquakes
• Gravitational force of the Moon and Sun.

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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

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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

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Wavelength
Crest
Wave Height
Still Water
Trough
Wave Parts
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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.

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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.

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Wave Movement

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

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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

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What is the Tidal Range?

• HT 30 ft, LT 20 ft
• HT 20 ft, LT 12 ft
• HT 50 ft, LT 20 ft

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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.

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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

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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

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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

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Complete the Types of Tides worksheet

• The End