1. (Discussion – The Ocean in Motion: Tides)
Wednesday, January 31, 2018
(Discussion – The Ocean in Motion: Tides)

2. Describe how a wave “breaks.”
The Launch Pad
Wednesday, 1/31/18
1/1
Describe how a wave “breaks.”
As a wave approaches the shore, its energy is squeezed into a smaller and smaller space vertically.
The water at the bottom of the wave slows down due to friction from the sea floor.
Now, the water at the top of the wave is moving faster than the water at the bottom and the wave falls forward.

3. Remediation for Quiz 10 runs through Friday!
Announcements
Remediation for Quiz 10 runs through Friday!

4. Summative or Formative #
Assignment
Summative or Formative #
Date Issued
Gone Missing Day
Last Day Accepted
QUIZ 10 S1
1/26
Friday

5. Discussion - The Ocean in Motion
Tides
REMINDER: All slides regarding the oceans are on the class website in two separate PowerPoints:
The Hydrosphere - Seawater and Currents
The Hydrosphere - Waves, Tides, and Deep Ocean Exploration

6. The Ocean in Motion
Tides

7. Tides Learning Objectives What is a tide?
What are the different types of tidal patterns?
What causes tides?
What are the different types of tides?
Where is the largest tide on Earth found?
What is the Saltstraumen?

8. Tides are 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

9. 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

10. 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)
For complete technical accuracy, the type of day referred to in the definitions for diurnal, semidiurnal, and mixed (semidiurnal) tides is a lunar day (also referred to as a tidal day). A lunar day is 24 hours and 50 minutes compared to the typical solar day which is 24 hours. It refers to the time required for a spot on earth to make a full rotation from a specific location under the moon to the same location (under the moon). For a more in depth explanation of a lunar day, see (Accessed, May 2011).

11. 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!)
Photo: NASA
Photo:
Accessed: November 2010

12. 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!)
Low tide
High tide
Photo: NASA
Photo:
Accessed: November 2010

13. What causes tides?
The gravitational pull of the sun and the moon causes “bulges” on Earth that move as we rotate
Gravitational pull
“Bulge”
of Earth
Sun
Earth
Moon
Teacher’s Note: The slide labels the gravitational pull and bulge of the Earth as you advance the slide.

14. What causes tides?
The tide rises when coastline enters the bulge and falls when it rotates out
High tide

15. 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 tides

16. Different types of tide
Earth
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?
Teacher’s Note: Even though the sun is larger than the moon, the moon’s pull is always greater because the moon is much closer to the earth.
Sun
Moon

17. Figure 1: Tide predictions for Dauphin Island, 3/1/11
Water Level (ft)
Figure 1: Shows tidal predictions for Dauphin Island, AL 3/1/11 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day
What time does the first low tide occur? (8:00 a.m.)
What time does the first high tide occur? (8:00 p.m.)
How many high tides and low tides occur? (one high tide and one low tide)
What type of tide do you think this is? (Diurnal)
Time

18. Figure 1 shows a diurnal tide: one high and one low tide
First high tide ~8pm
Water Level (ft)
Figure 1: Shows tidal predictions for Dauphin Island, AL 3/1/11 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day
What time does the first low tide occur? (8:00 a.m.)
What time does the first high tide occur? (8:00 p.m.)
How many high tides and low tides occur? (one high tide and one low tide)
What type of tide do you think this is? (Diurnal)
First low tide ~8am
Time

19. Figure 2: Tide predictions for Woods Hole, MA, 8/25/10
Water Level (ft)
Figure 2: Shows tidal predictions for Woods Hole, MA 8/25/10 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day
How many high tides are present? (2)
What times do they occur? (~9:00 a.m. and ~9:00 p.m.)
How many low tides are present? (2)
What times do they occur? (4:00 a.m. and 4:00 p.m.)
What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (2 feet)
What is the tidal range for the second high and low tide (round to nearest foot)? (2 feet)
What type of tide is this? (Semidiurnal – 2 high and low tides of about equal heights)
Time

20. Figure 2 shows a semidiurnal tide: two high and low tides of equal heights
First high tide ~9am
Second high tide ~9pm
Tidal range 2ft
Tidal range 2ft
Water Level (ft)
Figure 2: Shows tidal predictions for Woods Hole, MA 8/25/10 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time in hourly increments over the course of a day
How many high tides are present? (2)
What times do they occur? (~9:00 a.m. and ~9:00 p.m.)
How many low tides are present? (2)
What times do they occur? (4:00 a.m. and 4:00 p.m.)
What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (2 feet)
What is the tidal range for the second high and low tide (round to nearest foot)? (2 feet)
What type of tide is this? (Semidiurnal – 2 high and low tides of about equal heights)
Second low tide ~4pm
First low tide ~4am
Time

21. Figure 3: Tide predictions for Seattle, WA (Puget Sound), 5/1/11
Water Level (ft)
Figure 3: Shows tidal predictions for Seattle, Washington (Puget Sound) 5/1/11 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time hourly increments over the course of a day
How many high tides are present? (2)
What times do they occur? (~4:00 a.m. and ~6:00 p.m.)
How many low tides are present? (2)
What times do they occur? (11:00 a.m. and 11:00 p.m.)
What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (10 feet)
What is the tidal range for the second high and low tide (round to nearest foot)? (4 feet)
What type of tide is this? (Mixed Semidiurnal – 2 high and low tides of unequal heights)
Time

22. Figure 3 shows a mixed semidiurnal tide: two high and low tides of unequal heights
Second high tide ~6pm
First high tide ~4am
Tidal range 4ft
Tidal range 10ft
Second low tide ~11pm
Water Level (ft)
Figure 3: Shows tidal predictions for Seattle, Washington (Puget Sound) 5/1/11 Local Standard Time (LST) – Data comes from station (
Y-axis shows water levels in feet and x-axis shows time hourly increments over the course of a day
How many high tides are present? (2)
What times do they occur? (~4:00 a.m. and ~6:00 p.m.)
How many low tides are present? (2)
What times do they occur? (11:00 a.m. and 11:00 p.m.)
What is the tidal range (distance between high and low tide) for first high and low tide (round to nearest foot)? (10 feet)
What is the tidal range for the second high and low tide (round to nearest foot)? (4 feet)
What type of tide is this? (Mixed Semidiurnal – 2 high and low tides of unequal heights)
First low tide ~11am
Time

23. The Saltstraumen https://www.youtube.com/watch?v=Ci-uwzFIsgE
The Saltstraumen has the strongest tidal current in the world. Up to 520,000,000 cu. yd. of seawater forces its way through a 1.9 mile long and 490 foot wide strait every six hours, with water speeds reaching 25 mph. Vortices known as whirlpools (or maelstroms) up to 33 feet in diameter and 16 feet in depth are formed when the current is at its strongest. The Saltstraumen has existed for about two to three thousand years. Before that, the area was different due to post-glacial rebound. The current is created when the tide tries to fill the Skjerstadfjorden. The height difference between the sea level and the fjord inside can be up to 3 ft 3 in. When the current turns, there is a period when the strait is navigable.

24. A tide is the periodic rise and fall of a body of water.
Tides
Summary
What is a tide?
A tide is the periodic rise and fall of a body of water.

25. What are the different types of tidal patterns?
Tides
Summary
What are the different types of tidal patterns?
diurnal tides - one low tide and one high tide per day
semidiurnal tides - two high and low tides per day approximately equal in size
mixed semidiurnal tides - two high and low tides of unequal size

26. Tides What causes tides?
Summary
What causes tides?
Tides are caused by the gravitational pull of the sun and the moon that cause “bulges” on Earth.
The tide rises when coastline enters the bulge and falls when it rotates out

27. What are the different types of tides?
Summary
What are the different types of tides?
Spring tides occur when the sun and moon are in a straight line
Neap tides occur when the sun and moon form a right angle with Earth

28. Where is the largest tide on Earth found?
Tides
Summary
Where is the largest tide on Earth found?
The Bay of Fundy in Canada is known for its large tidal range (differences of over 50ft have been recorded!)

29. Tides What is the Saltstraumen?
Summary
What is the Saltstraumen?
The Saltstraumen has the strongest tidal current in the world.