Tides Exercise - Biology 317 - Field Marine Biology (Due on Wednesday Jan. 28, 2015 - 5 pts.)

This exercise introduces a phenomenon central to our course: the tides. Answer the following questions, using the tide table linked here (tip: bookmark this link in your web browser!)

1. In the tide table linked above, find and list the times (24 hour format) and tidal heights (in feet) for the four tides for the 1st Friday of the semester. Repeat for the 2nd Friday of the semester.

1st Friday: a)____:____  _________ft. b)____:____  _________ft. c)____:____  _________ft. d)____:____  _________ft.

2nd Friday: a)____:____  _________ft. b)____:____  _________ft. c)____:____  _________ft. d)____:____  _________ft.

Note: If you need to change which month is displayed, follow these instructions exactly:

       a) scroll down to below the month-format tide table displayed to find "Starting time and time display options".

       b) use pull-down menu there to change to the desired month that you want to display (don't worry about changing the day).

       c) scroll back up to show bottom of tide table and click on the button "Make Prediction Using Options".

2. Display three days of tides surrounding the 1st Friday (Thursday to Saturday) as follows.

       a) scroll down to below the month-format tide table displayed to find "Starting time and time display options".

       b) use pull-down menus for month and day after "Start at" to select date for 1st Thursday (leave time at 00:00)

       c) scroll up to "Select display type" and change selection from "One-Month Calendar" to "Graphical Plot".

       d) scroll down to "Select presentation options" and set "Length of time to display" to "3 days".

       e) scroll down to "Select options for plots" and select "Plot with lines only, not color-filled".

       f) scroll back up to show bottom of tide table and click on the button "Make Prediction Using Options".

3. Draw a reproduction of this graph carefully, preferably on the top half of a piece of graph paper (you can print out one here). Your y axis should be tidal height in feet, with values ranging from -3 ft at the origin to about 8 ft. Your x axis should be spaced to span three days, labeling every six hours (i.e., 0, 6, 12, 18, 0, 6, 12, 18, 0, 6, 12, 18, 0).

4. (Optional) To do #3 most effectively, follow these steps:

       a) Scroll to "Select display type" and change selection to "Strict Intervals" choosing "2 hours" for the interval time.

       b) Scroll back up to show bottom of tide table and click on the button "Make Prediction Using Options".

       c) Plot the displayed data on your graph, also plotting the data points corresponding to high and low tides.

5. True/False (circle one) The tidal height is changing faster midway between high and low tide than it is at or near low tide.

6. What is the duration between the first Thursday's LLW and the 1st Friday's LLW tide? Please be as precise as possible.

7. Study what is mean by mixed tides in our text (p. 41). Explain what this means in terms of the observed tidal cycles. Please note that the typical pattern is abbreviated in the following order: HHW, LLW, LHW, HLW, so the most extreme low tide directly follows the most extreme high tide. Apply these labels to each of your graphs.

8. Repeat steps 2-4 starting with the 2nd Thursday (i.e., make a graph for tides spanning three days, one week later).

9. Study the difference between "spring" and "neap" tides after reading the section on tides in our text (p. xx). Assign one of these terms to each of the graphs that you drew. Explain your assignments in terms of the lunar cycle (i.e., new, first quarter, full, third quarter) in the following space:

 

 

 

 

10. In terms of how low the tides during our Friday afternoon field trips, how does the better of the 1st or 2nd Friday lower low tides compare with upcoming low tides (3rd to 15th Fridays)? (Hint: You can also consult our course field trip schedule.)