Tides
Tides The Largest Waves in the Ocean
Understanding Tides
Understanding Tides You will study several topics: Why Earth has tides Why tides vary daily Why tides vary monthly
Tide Generation
Tide Generation Two principle factors generate tides:
Tide Generation Two principle factors generate tides: 1. Gravitational attraction
Tide Generation Two principle factors generate tides: 1. Gravitational attraction 2. Inertia
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
Gravitational attraction holds Earth and the moon in their orbits
Gravitational attraction also pulls the ocean towards the moon
Gravitational Attraction
Gravity Bulge
Earth-Moon System
Earth-Moon System The moon does not revolve around Earth
Earth-Moon System The moon does not revolve around Earth Earth and the moon revolve one another
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
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
Center of Mass
Center of Mass Earth is 81x more massive than the moon
Center of Mass Earth is 81x more massive than the moon Therefore, the Earth-Moon system center of mass is inside Earth
Inertia
Inertia Bulge
Two Tide Bulges
Two Tide Bulges Inertia bulge Gravity bulge
Two Tide Bulges
Two Tide Bulges One towards the moon: the gravity bulge One on the opposite side from the moon: the inertia bulge
Two Tide Bulges
Tidal Variability
Tidal Variability Tides vary on several cycles: 1. Daily 2. Monthly 3. and longer periods - years and decades
Daily Tide Variations
Daily Tide Variations Earth experiences daily tide variations for two reasons:
Daily Tide Variations Earth experiences daily tide variations for two reasons: 1. Earth rotates
Daily Tide Variations Earth experiences daily tide variations for two reasons: 1. Earth rotates 2. Earth and the moon revolve around each other
Earth Rotates
Earth Rotates Earth rotates every 24 hr - the solar day
First Daily High Tide
First Daily High Tide Earth rotates into the gravity bulge:
First Daily High Tide Earth rotates into the gravity bulge: high tide
First Daily Low Tide
First Daily Low Tide Earth rotates into a tide trough:
First Daily Low Tide Earth rotates into a tide trough: low tide
Second Daily High Tide
Second Daily High Tide Earth rotates into the inertia bulge:
Second Daily High Tide Earth rotates into the inertia bulge: high tide
Second Daily Low Tide
Second Daily Low Tide Earth rotates into a tide trough:
Second Daily Low Tide Earth rotates into a tide trough: low tide
Daily Tide Variations
Daily Tide Variations Hawai i experiences two high tides and two low tides daily
As Earth rotates every 24 hr, the moon moves a little in its orbit around Earth
Earth must rotate for an additional 50 minutes to return to the same position with respect to the moon
The same point in the tides comes 24 hr 50 min later the following day
The solar day is 24 hr The lunar day is 24 hr 50 mim
Daily Tide Variation May 2 May 3
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
Earth and the moon revolve around one another every 29.5 days - the lunar month
Two Sun Tide Bulges
Two Sun Tide Bulges The sun also generates two tide bulges
Two Sun Tide Bulges The sun also generates two tide bulges One towards the sun and one on the opposite side of Earth
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
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
Monthly Tide Variation
Monthly Tide Variation Earth experiences four tide crests and four tide troughs:
Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests
Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests Two large moon troughs
Monthly Tide Variation Earth experiences four tide crests and four tide troughs: Two large moon crests Two large moon troughs Two small sun crests
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
Interference of the lunar crests and troughs and the solar crests and troughs cause large variations in the tidal range throughout the lunar month
Interference of the lunar crests and troughs and the solar crests and troughs cause large variations in the tidal range throughout the lunar month
Spring Tides
Spring Tides Spring tides occur during new moon and full moon
Spring Tides Spring tides occur during new moon and full moon The lunar and solar crest line up
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
Neap Tides
Neap Tides During neap tides, the lunar crests coincide with the solar troughs and vice versa
Neap Tides
Neap Tides Neap tides occur during first quarter moon and third quarter moon
All Pau