CHAPTER 24: OCEAN TIDES AND TIDAL RANGES LAB INVESTIGATION

Learning Targets

  • Plot and graph tide data for three different locations
  • Compare & analyze datafortides at three different locations

Background Information:

For most coastal locations, high tides and low tides follow each other ina regular pattern. The level of the water at each high tide and at each lowtide, however, varies from day to day and from location to location. Inthe same way, the difference in water level between high tide and low tide,called the tidal range, is constantly changing. The greatest tidal rangesoccur near the times of the new moon and the full moon when the sun, moon and earth are aligned. They are calledspring tides. The smallest tidal ranges occur near the times of the quartermoon phases where the moon and sun are at right angles to the Earth. They are called neap tides.

Another factor that influences tidal range is the shape of the bay inwhich the tide occurs. Bays that narrow away from the oceancause the water level to rise higher as the tide moves into the bay. Suchbays tend to have a large tidal range. Bays that have narrow openings to the ocean and remain narrow also tend to have a large tidal range because the water is more compressed as it travels up the bay and are more exaggerated. On the other hand, bays thatwiden away from their entrance tend tohave small tidal ranges. The last factor that influences tides is the size of the body of water. The moon’s pull has a greater effect on large bodies of water. For example, the Great Lakes do not experience high and low tide because they contain a small mass of water compared an ocean.

Procedures – This activity examines the tides at three locations:

Bay / Location / Water Body Shape
Boston Harbor / Boston, Massachusetts / Wide opening into Atlantic, narrows away from the ocean
Bay of Fundy / Saint John,
New Brunswick / Narrow opening into Atlantic and remains narrow
Mobile Bay / Mobile, Alabama / Narrow opening into the Gulf of Mexico, widens away from the Gulf
  1. The tables on the next page contain data for the spring and neap tides for the three different locations. Find thetide data for Boston at spring/neap tide. Choose one color to plotthe data for the spring tide and another color to plot the data for neap tide on the Spring and Neap Tide at Boston,MAgraph. Connect each point with a smooth line curve in the chosen color. Include a color-code key.
  1. Using the same colored code, plot the data for both the spring tides and neap tides on the Spring and Neap Tide Saint John and Mobilegraphs. Notice that the water level scale changes!! Connect each point with a smooth line curve.
  1. Answer the Analysis and Conclusion questions after graphs are complete.

Spring & Neap Tide Data Tables

MOBILE, AL
Time (hour) / Spring Tide Water Level (m) / Neap Tide Water Level (m)
0 / 0.43 / 0.31
2 / 0.53 / 0.36
4 / 0.54 / 0.37
6 / 0.45 / 0.32
8 / 0.3 / 0.23
10 / 0.12 / 0.14
12 / -0.02 / 0.06
14 / -0.10 / 0.03
16 / -0.12 / 0.03
18 / -0.08 / 0.06
20 / 0.03 / 0.13
22 / 0.18 / 0.22
24 / 0.34 / 0.31
BOSTON, MA
Time (hour) / Spring Tide Water Level (m) / Neap Tide Water Level (m)
0 / 2.4 / 1.6
2 / 3.5 / 2.3
4 / 3.4 / 2.3
6 / 1.4 / 1.5
8 / -0.2 / 0.8
10 / -0.2 / 0.8
12 / 1.4 / 1.7
14 / 3.1 / 2.1
16 / 3.1 / 2.1
18 / 1.7 / 2.0
20 / 0.5 / 1.0
22 / -0.3 / 0.6
24 / 0.6 / 1.2
SAINT JOHN, NB
Time (hour) / Spring Tide Water Level (m) / Neap Tide Water Level (m)
0 / 4.5 / 4.5
2 / 7.7 / 6.3
4 / 7.8 / 6.2
6 / 5.1 / 4.4
8 / 1.5 / 2.5
10 / 1.5 / 2.5
12 / 4.0 / 4.4
14 / 7.5 / 5.9
16 / 7.5 / 6.1
18 / 5.6 / 4.2
20 / 3.2 / 3.2
22 / 0.5 / 2.2
24 / 1.6 / 3.3


Analysis and Conclusions:

**Base your answers on the graphs and the information found in the introduction.**

1. How does the maximum water level for spring tidescompare with the maximum water level for neap tides?

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2. How are the Earth, the Sun, and the Moon aligned during spring tide?How are they aligned during neap tide?

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3) Calculate the Tidal Rangeduring Spring Tidefor each location:

—TheTidal Range isthe difference in water level between high tide and low tide.

(So take the highest water level minus the lowest water level.Careful with the negative numbers!)

Bay / Location / Tidal Range (m)
Boston Harbor / Boston, Massachusetts
Bay of Fundy / Saint John,
New Brunswick
Mobile Bay / Mobile, Alabama

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4) If you calculated the tidal rangefor neap tide would it be higher or lowerthan the spring tide tidal range? Why?

______4 Lab Activity Laboratory Manual

5) How does the alignment of the Earth, Sun and Moon affect the tidal range?

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6) Which location has the greatest tidal range? ______thesmallesttidal range? ______

7) Both Boston Harbor and the Bay of Fundy are located on the Atlantic ocean. Explain why the Bay of Fundy has a greater tidal range.

______

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8) Mobile Bay is located in the Gulf of Mexico.Boston Harborand the Bay of Fundy open into the AtlanticOcean. Why does Mobile Bay have such a small tidal range?

______

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9) Based on your graphs:How long is the interval between high tides in Boston? ______

How long is the interval between high tides in Saint John? ______

How long is the interval between high tides in Mobile? ______

10) How many high tides per day (24hrs) occur in Boston? ______Saint John?______Mobile?______

Explain the reason for the differences: ______

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Name: ______Date: ______Block: ______