Interpreting Tidal Data
Integrated Science 1Name:Period:
Background
The level of San Francisco Estuary is constantly changing. In fact, these regular and predictable fluctuations occur all around the globe and are called the tides. The tides are so predictable that daily tide tables are available for an entire year and may actually be calculated years in advance. The daily, monthly, and seasonal tidal patterns of the San Francisco Estuary are absolutely critical in the overall ecology of the bay. The tides influence the salinity in all parts of the estuary, which limits the types and numbers of organisms, which may exist in any particular area.
In this activity, you will use tide tables for a single month as your data. This data will then be represented in graphical form for a clearer and more visual analysis. Students will interpret tidal data using tidal charts and tidal graphs.
Focus Questions
• What is the nature of the daily, and monthly tidal cycles?
• Why do the tides change on daily, and monthly cycles?
• What are the major effects of these tidal fluctuations on the bay/estuary?
Procedure
1.Tide Table Information: Location:Month:
2. Use the provided chart and graph to answer the following questions.
Interpreting Data
Use both your tidal chart and your tidal graph to answer the following questions. All heights are in METERS.
1. Tidal Range is the difference, in feet, between consecutive high and low tides.
What is the highest tidal range for October 31? ______
What is the lowest tidal range for October 9? ______
2. What is the highest level (height) that tides in the Corte Madera creek will reach in October? ______. On what date(s) will that happen? ______?
3. What is the lowest level (height) that tides in the Corte Madera creek will reach in October? ______. On what date(s) will that happen? ______?
4. Do tides all occur at 6 AM, noon, 6 PM (18), or midnight? Explain why or why not.
5. You will notice that on October 1, 7, 14, and 22 there are only three tides written in the chart. Analyze the graph and explain why this is the case.
Discussion/ Conclusion
1.Describe, in words, the tidal pattern that the tidal graph depicts.
2.Select one date that appears to have a large tidal range and one that appears to have a small tidal range. Complete the information below.
Large Tide Range: Date: High Tide: Low Tide: Diff:
Small Tide Range: Date: High Tide: Low Tide: Diff:
b) What would you expect the phase of the moon to be for those tides?
Large Tide Range: Moon Phase - or - Moon Percent:
Small Tide Range: Moon Phase - or - Moon Percent:
3.Record the definitions for spring and neap tides (either from your notes or from your Textbook). Then indicate on the graph which are spring tides and which are neap tides.
Spring Tide:
Neap Tide:
4.Specifically, how are the tides influenced by the moon? (explain what is happening to create both bulges)
5.As a result of the daily tidal cycle what particular problems are faced by organisms that live in inter-tidal areas such as mudflats and tide pools? How might these problems be different during the rainy season?
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Interpreting Tidal Data