Tides Webquest - hannah's notebook



Tides Webquest

Part I: Background on Tides

Begin your information search by using your textbook and accessing

As you read through the tutorial, answer the questions below that correspond to each section of the tutorial.

What are Tides?

1. What is a basic definition of a tide? Tides are very long-period waves that move through the oceans in response to the forces exerted by the moon and sun.

2. What is a high tide? What is a low tide? High tide occurs when the highest part, or crest of the wave reaches a particular location. Low tide corresponds to the lowest part of the wave, or its trough.

3. What is tidal range? It is the difference of height between the high tides and the low tides

What Causes Tides?

6. Tides are caused by the gravitational attraction of what two celestial bodies? It is Newton’s law of universal gravitation

7. What does Newton’s law of universal gravitational state? It states that the gravitational attraction between two bodies is directly proportional to their masses, and inversely proportional to the square of the distance between the bodies.

8. Which celestial body has a greater effect on tidal forces on Earth? Gravitational attractive forces

Gravity, Inertia, and the Two Bulges

9. How does the moon create a bulge? When the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon

10. What causes a bulge to be created on the opposite side of the Earth or the “far side” from the moon? When the gravitational attraction of the moon is less because it is farther away

Changing Angles and Changing Tides

11. Describe how changes in the relative positions of the moon and sun change in relation to the Earth? The moon moves around the Earth once every 28 days.

The Earth and moon move around the sun every 365 days.

12. At what point is the sun at its minimum declination and its maximum declination? During the vernal and autumnal equinoxes—March 21 and September 23, respectively—the sun is at its minimum declination.

On June 21 and December 22—the summer and winter solstices, respectively—the sun is at its maximum declination

Frequency of Tides - The Lunar Day

15. Compare and contrast a solar and lunar day. How long is a lunar day? Unlike a solar day, however, a lunar day is 24 hours and 50 minutes. The lunar day is 50 minutes longer than a solar day because the moon revolves around the Earth in the same direction that the Earth rotates around its axis. A lunar day lasts 24 hours and 50 minutes.

16. Why do most coastal areas experience two high tides and two low tides? Because the Earth rotates through two tidal “bulges”.

17. How long does it take for high tide to occur? How long is the time between low and high tide? High tides occur 12 hours and 25 minutes apart. . It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high.

Tidal Variations - The Influence of Position and Distance

18. What causes spring tides? What causes neap tides? How many spring and neap tides occur in a lunar month? Spring tides are a tide just after a new or full moon, when there is greatest difference between high and low tide. Neap tides are caused by the sun and moon are at right angles to each other, the solar tide partially cancels out the lunar tide and produces moderate tides known as neap tides. 2 spring and neap tides occur a year.

19. How are tide-generating forces affected when the moon is closest to the Earth (or perigee)? when the moon is farthest away from the Earth (or apogee)? How does this affect the tides that are produced? When the moon is closest to the earth tide-generating forces are higher than usual, producing above-average ranges in the. When the moon is farthest from the earth the lunar tide-raising force is smaller, and the tidal ranges are less than average.

20. How are tide-generating forces affected when the Earth is closest to the sun (or perihelion)? when the Earth is farthest from the sun (or aphelion)? How does this affect the tides that are produced? The tidal ranges are enhanced when earth is closest to the sun. When the earth is farthest away from the sun the tidal ranges are reduced.

What Affects Tides in Addition to the Sun and Moon?

21. How are the magnitudes of tides affected by shorelines? By mid-ocean islands? At a smaller scale, the magnitude of tides can be strongly influenced by the shape of the shoreline. Mid-oceanic islands not near continental margins typically experience very small tides of 1 meter or less.

22. How does a funnel-shaped bay compare to a narrow inlet and shallow water?

Funnel-shaped bays in particular can dramatically alter tidal magnitude. The Bay of Fundy in Nova Scotia is the classic example of this effect, and has the highest tides in the world—over 15 meters.

23. What is the affect of strong tidal rivers on tides in estuaries? In estuaries with strong tidal rivers, flow in the spring can severely alter or mask the incoming tide.

24. What other abiotic factors affect tides? Compare and contrast wind and weather patterns that affect tides. Local wind and weathering can also affect tides. Strong offshore winds can move water away from coastlines, exaggerating low tide exposures.

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