tides. what is a tide? a tide is the periodic rise and fall of a body of water due to gravitational...
TRANSCRIPT
![Page 1: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/1.jpg)
TIDES
![Page 2: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/2.jpg)
What is a tide?
• A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth
• The wavelength of an average tide can be up to 17,000 km (over 10,500 miles). Do you think tides are deepwater or shallow water waves?
• Shallow water! Recall that shallow-water waves have Depth < 1/20 Wavelength and deepwater waves have Depth > 1/2 Wavelength
• The ocean would have to be deeper than 5,250 miles for an ocean tide to be a deepwater wave!
2
![Page 3: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/3.jpg)
1.Gravitational pull of the moon and sun
2.Centripetal force of the rotating Earth
Tides are generated by:
![Page 4: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/4.jpg)
Tides are generated by:• the gravitational pull of the moon and sun
- moon has 2x greater gravitational pull than the sun - sun is 10 million x more massive than the
moon and is 390 times farther away
![Page 5: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/5.jpg)
“Bulge” of Earth
What causes tides?
The gravitational pull of the sun and the moon causes “bulges” on Earth that move as we rotate
Sun
Earth
Moon
Gravitational pull
5
![Page 7: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/7.jpg)
CENTRIPETAL
GRAVITATIONAL FORCE
GRAVITATIONAL & CENTRIPETAL
![Page 8: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/8.jpg)
What causes tides?
The tide rises when coastline enters the bulge and falls when it rotates out
High tide
8
![Page 9: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/9.jpg)
• High water: a water level maximum ("high tide") • Low water: a water level minimum ("low tide") • Tidal range: the difference between high and low tide
Description of tides
Intertidal zoneHigh tide
Low tide
![Page 10: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/10.jpg)
Alma at High Tide
Alma at Low Tide
![Page 11: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/11.jpg)
Earth-Moon-Sun positions and the monthly tidal cycle
Spring TideHighest high tide and lowest low tide
Neap TideModerate tidal range
![Page 12: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/12.jpg)
Different types of tide
Sun
Earth
Moon
• Spring tides occur when the sun and moon are in a straight line
• The tidal range is typically highest during spring tides12
![Page 13: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/13.jpg)
Different types of tide
• Neap tides occur when the sun and moon form a right angle with Earth
• Low tides are typically higher and high tides are lower
• Why is the moon’s pull greater than the sun’s?
Earth
Moon
Sun
13
![Page 14: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/14.jpg)
![Page 15: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/15.jpg)
![Page 16: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/16.jpg)
Tides are also important physical forces in our ocean
• Gravitational interactions between the sun, moon and earth are the primary causes of tides
• Different positions of the sun and moon create two different types of tides: spring tides and neap tides
• Tides play an important role in the life cycle of many marine organisms
16
![Page 18: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/18.jpg)
The Bay of Fundy: Site of the world’s largest tidal range
• Tidal energy is focused by shape and shallowness of bay
• Maximum spring tidal range in Minas Basin = 17 meters (56 feet)
![Page 19: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/19.jpg)
Tidal extremes: The Bay of Fundy
The Bay of Fundy in Canada is known for its large tidal range (differences of over 50ft have been recorded!)
High tideLow tide
Photo: NASA
19
![Page 20: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/20.jpg)
Tidal patterns vary around the world
• Some places have one low tide and one high tide per day (diurnal tides)
• Other places have two high and low tides per day approximately equal in size (semidiurnal tides)
• If the two high and low tides of a semidiurnal tide are unequal in size, they are call mixed semidiurnal tides
• The US has examples of semidiurnal tides (East Coast), diurnal tides (some areas of the Gulf of Mexico) and mixed tides (Pacific Coast)
20
![Page 21: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/21.jpg)
Tide exercise: Can you identify the different types of tides?
21
• You will be presented with three figures and corresponding questions
• See if you can determine which figures represent diurnal, semidiurnal and mixed semidiurnal tides.
![Page 22: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/22.jpg)
Figure 1: Tide predictions for Dauphin Island, 3/1/11
22
Water Level (ft)
Time
![Page 23: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/23.jpg)
Figure 1 shows a diurnal tide: one high and one low tide
23
Water Level (ft)
Time
First low tide~8am
First hightide~8pm
![Page 24: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/24.jpg)
Figure 2: Tide predictions for Woods Hole, MA, 8/25/10
24
Water Level (ft)
Time
![Page 25: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/25.jpg)
Figure 2 shows a semidiurnal tide: two high and low tides of equal heights
25
Water Level (ft)
Time
First low tide~4am
First high tide~9am
Secondhigh tide~9pm
Second low tide~4pm
Tidal range2ft
Tidal range2ft
![Page 26: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/26.jpg)
Figure 3: Tide predictions for Seattle, WA (Puget Sound), 5/1/11
26
Water Level (ft)
Time
![Page 27: TIDES. What is a tide? A tide is the periodic rise and fall of a body of water due to gravitational interactions between the sun, moon and Earth The wavelength](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d1a5503460f949efe0e/html5/thumbnails/27.jpg)
Figure 3 shows a mixed semidiurnal tide: two high and low tides of unequal heights
27
Water Level (ft)
Time
First high tide~4am
Second high tide~6pm
First low tide~11am
Secondlow tide~11pm
Tidal range10ft
Tidal range4ft