Explain which types of tides are found in the United States?

The purpose of this activity is to learn how to graph tidal data from locations in the United States and to interpret your results.

In this activity, you will compare and contrast semidiurnal, diurnal, and mixed tides.

You will be able to answer these questions:

• How are tides affected by their location?

• Which types of tides are found in the United States?

• What causes that pattern?
There are two acceptable methods for completing the project, one using Excel/any other spreadsheet and one using a manual approach that does not require the use of a spreadsheet. Please read the instructions carefully. It is possible to do this project without using a spreadsheet if you do all of the calculations and graphing by hand. However, Excel/spreadsheet is recommended for this assignment.

National Oceanic and Atmospheric Administration (NOAA) data sets from widely separated tide stations are included. The tidal data were obtained from the National Oceanic Survey of NOAA website: tides and currents

The data sets cover hourly water level values over a one-month period from December 1 through December 31, 2014. As the data header shows, the times are Greenwich Mean Time (GMT), not local time, and the water levels are in feet.

Compare tidal information from the following sites:

Anchorage, Alaska

New London, Connecticut

Key West, Florida

Eagle Point, Texas

For each of the sites above, click on the link to open the file of data. After it opens, choose “Save Page As” (which is under File menu), then save the file to a folder on your hard drive or flash drive. Repeat this process for each of the text files.

Instructions (Using Excel):

Using the Guam tidal data as a sample, follow these instructions for importing tidal data into Excel.

Guam Tidal Data

Importing Tides Data [PDF file size 494.4 KB]

Once you are comfortable with importing tidal data into Excel, you can follow the same procedure for the other four data sets. You are graphing a 31-day period and a shorter (4- to 10-day period) for each of the four locations. Remember, to graph a shorter period, you must first select a smaller range of data.

Import all your graphs into a Word document, and complete your write up using the American Psychological Association (APA) style (6th edition).

Instructions (Without Excel):

Plot graphs of each of the stations over the 31-day period and the shorter 4- to 10-day period as outlined above.

Plan out your whole set of graphs before you start so you don’t have to redo them because of poor scale choices. Use graph paper or grid paper.

When plotting the longer interval, you don’t need to plot every hourly point; just plot about every three hours unless there is a maximum or minimum point in between these points. Include all four sites on the same graph or on four separate graphs that are aligned by time. Clearly label the graphs and scales.

It will be necessary to scan the graphs and submit them electronically with your Word document.

Once you plot the data (by either method), discuss the type of tide at each location and the comparison including relative height, tide type, and time differences of high tides and the phases of the moon. There are many websites that can calculate moon phases, such as Phases of the Moon and Moon Phases.

In your report, include a comparison of the sites over the 31-day period. Also include a comparison over a smaller time scale of 4 to 10 days. This shorter duration will allow you to see the tidal fluctuations in more detail. Your comparison should also relate to the phases of the moon for the period covered by the data, in other words, how are the phases of the moon and tidal waves related? Your comparison should include graphs using the exact same vertical scale (water level range) so that you can see the difference in tidal range between stations. It may include graphing all four sites on the same graph or on four separate graphs that are aligned by time.

Use the American Psychological Association (APA) style (6th edition) for writing your assignment.

Compose your work using a word processor (or other software as appropriate) and save it frequently to your computer. Be sure to check your work and correct any spelling or grammatical errors before you upload it. When you are ready to submit your work, click “Browse My Computer” and find your file. Once you have located your file, click “Open” and, if successful, the file name will appear under the Attached files heading. Scroll to the bottom of the page and click “Submit.”


• National Oceanic and Atmospheric Administration (NOAA). (n.d.). Tides and currents. Retrieved from http://tidesandcurrents.noaa.gov/

• Astronomical Applications Department of the U.S. Naval Observatory. (n.d.). Phases of the Moon. Retrieved from http://aa.usno.navy.mil/data/docs/MoonPhase.php

• StarDate. (n.d.). Moon phases. The University of Texas McDonald Observatory. Retrieved from http://stardate.org/nightsky/moon
Evaluation Criteria

Read the Natural Science Assignment Rubric [PDF file size 175 KB] to understand expectations for this assignment. These assignments, together, make up 10% of the total course grade.

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