Tides The Largest Waves in the Ocean

Transcription

1 Tides

2 Tides The Largest Waves in the Ocean

3 Understanding Tides

4 Understanding Tides You will study several topics: Why Earth has tides Why tides vary daily Why tides vary monthly

5 Tide Generation

6 Tide Generation Two principle factors generate tides:

7 Tide Generation Two principle factors generate tides: 1. Gravitational attraction

8 Tide Generation Two principle factors generate tides: 1. Gravitational attraction 2. Inertia

9 Tide Generation Two principle factors generate tides: 1. Gravitational attraction 2. Inertia Note that when discussing tides, inertia commonly is referred to as a centrifugal force

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11 Gravitational attraction holds Earth and the moon in their orbits

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13 Gravitational attraction also pulls the ocean towards the moon

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15 Gravitational Attraction

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17 Gravity Bulge

18 Earth-Moon System

19 Earth-Moon System The moon does not revolve around Earth

20 Earth-Moon System The moon does not revolve around Earth Earth and the moon revolve one another

21 Earth-Moon System The moon does not revolve around Earth Earth and the moon revolve one another Earth and the moon revolve around the Earth-Moon system center of mass

22 Earth-Moon System The moon does not revolve around Earth Earth and the moon revolve one another Earth and the moon revolve around the Earth-Moon system center of mass The Earth-Moon system center of mass is inside Earth

23 Center of Mass

24 Center of Mass Earth is 81x more massive than the moon

25 Center of Mass Earth is 81x more massive than the moon Therefore, the Earth-Moon system center of mass is inside Earth

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28 Inertia

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30 Inertia Bulge

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32 Two Tide Bulges

33 Two Tide Bulges Inertia bulge Gravity bulge

34 Two Tide Bulges

35 Two Tide Bulges One towards the moon: the gravity bulge One on the opposite side from the moon: the inertia bulge

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37 Two Tide Bulges

38 Tidal Variability

39 Tidal Variability Tides vary on several cycles: 1. Daily 2. Monthly 3. and longer periods - years and decades

40 Daily Tide Variations

41 Daily Tide Variations Earth experiences daily tide variations for two reasons:

42 Daily Tide Variations Earth experiences daily tide variations for two reasons: 1. Earth rotates

43 Daily Tide Variations Earth experiences daily tide variations for two reasons: 1. Earth rotates 2. Earth and the moon revolve around each other

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45 Earth Rotates

46 Earth Rotates Earth rotates every 24 hr - the solar day

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48 First Daily High Tide

49 First Daily High Tide Earth rotates into the gravity bulge:

50 First Daily High Tide Earth rotates into the gravity bulge: high tide

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52 First Daily Low Tide

53 First Daily Low Tide Earth rotates into a tide trough:

54 First Daily Low Tide Earth rotates into a tide trough: low tide

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56 Second Daily High Tide

57 Second Daily High Tide Earth rotates into the inertia bulge:

58 Second Daily High Tide Earth rotates into the inertia bulge: high tide

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60 Second Daily Low Tide

61 Second Daily Low Tide Earth rotates into a tide trough:

62 Second Daily Low Tide Earth rotates into a tide trough: low tide

63 Daily Tide Variations

64 Daily Tide Variations Hawai i experiences two high tides and two low tides daily

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66 As Earth rotates every 24 hr, the moon moves a little in its orbit around Earth

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68 Earth must rotate for an additional 50 minutes to return to the same position with respect to the moon

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70 The same point in the tides comes 24 hr 50 min later the following day

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72 The solar day is 24 hr The lunar day is 24 hr 50 mim

73 Daily Tide Variation May 2 May 3

74 Daily Tide Variation May 2 May 3 High tide: 6:00 AM Low tide: 12:12 PM High tide: 6:24 PM Low tide: 12:36 AM High tide: 6:50 AM Low tide: 1:02 PM High tide: 7:14 PM Low tide: 1:26 AM

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76 Earth and the moon revolve around one another every 29.5 days - the lunar month

77 Two Sun Tide Bulges

78 Two Sun Tide Bulges The sun also generates two tide bulges

79 Two Sun Tide Bulges The sun also generates two tide bulges One towards the sun and one on the opposite side of Earth

80 Two Sun Tide Bulges The sun also generates two tide bulges One towards the sun and one on the opposite side of Earth The sun tide bulges are 40% as large as the moon tide bulges

81 Two Sun Tide Bulges The sun also generates two tide bulges One towards the sun and one on the opposite side of Earth The sun tide bulges are 40% as large as the moon tide bulges The moon controls Earth s tides because it is much closer than the sun

82 Monthly Tide Variation

83 Monthly Tide Variation Earth experiences four tide crests and four tide troughs:

84 Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests

85 Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests Two large moon troughs

86 Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests Two large moon troughs Two small sun crests

87 Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests Two large moon troughs Two small sun crests Two small sun troughs

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89 Interference of the lunar crests and troughs and the solar crests and troughs cause large variations in the tidal range throughout the lunar month

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91 Interference of the lunar crests and troughs and the solar crests and troughs cause large variations in the tidal range throughout the lunar month

92 Spring Tides

93 Spring Tides Spring tides occur during new moon and full moon

94 Spring Tides Spring tides occur during new moon and full moon The lunar and solar crest line up

95 Spring Tides Spring tides occur during new moon and full moon The lunar and solar crest line up And the lunar and solar troughs line up

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97 Neap Tides

98 Neap Tides During neap tides, the lunar crests coincide with the solar troughs and vice versa

99 Neap Tides

100 Neap Tides Neap tides occur during first quarter moon and third quarter moon

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102 All Pau