Lessons Index:
6. CHART MAKING FOR NAVIGATORS
Osher Map Library
University of Southern Maine
Charting Neptune's Realm:
From Classical Mythology to Satellite Imagery
An exhibition at the Osher Map Library and Smith Center for Cartographic Education, University of Southern Maine, Portland, 4 April 2000 to 11 January 2001
Donald S. Johnson, guest curator
SURFACE CURRENTS
Osher Map Library Lesson
Charting Neptune's Realm
Hope McVane
E. Presentation of the lesson
(Item) (Activity) (Time/Elapsed Time)
1. Opening Statement: (1 min/1 min)
Currents are the horizontal movement of ocean water. Very early
in the history of the United States the importance of currents
was realized. Ben Franklin first charted the Gulf Stream after
becoming concerned about the amount of time it took to sail from
the United States to England and back. He realized that there
was an "underwater stream," and that the fastest route
was not a straight line. Using information from sailors he plotted
the Gulf Stream, which was later created into ship courses by
John Elliot Pillsbury, one hundred years later.
In this lesson you will be looking at these charts to determine how they were able to identify the current as well as looking at modern maps of currents and prevailing winds. Using data provided we will then identify and plot a current.
2. Review plotting longitude and latitude with students.
3. Brainstorm ocean currents (10 min/11 min)
a. Determine
their previous knowledge.
b. Look
at the charts of Ben Franklin's and
John Elliot Pillsbury's Gulf Stream.
- How is the current identified?
- What information did they need?
- Have the students compare and contrast the charts.
- What did one hundred years difference make in chart formation?
- Have the students generate a list of differences in both charts
and hypothesize why the differences occur.
- What technology has caused the differences?
- Have students brainstorm a map created one hundred years from
now. What do they think would be different?
4. The Gulf Stream (10 min/21 min)
Focus on surface currents and the Gulf Stream. Use the overlay
transparencies to view global
prevailing winds and global
surface currents. Aid the students in determining warm and
cold surface currents.
5. Plotting Surface currents (2 min/23 min)
a. Identified
by temperature
b. Satellite
images to determine temperature
c. Buoys
located at certain longitude and latitude that take readings
of temperature, wave height, and weather conditions
6. Student Exercise (19 min/42 min)
Students may work in pairs, small groups or individually. Each
student should plot temperature readings at the correct longitude
and latitude to identify the Gulf Stream, the warm water current,
along the eastern coast of North America. Students will also
identify cold water between New England and the Gulf Stream,
causing the northeast United States to miss the benefit of the
warm air that the Gulf Stream brings with it. Once their chart
is completed, have students compare results with each other,
with a current map of global surface currents, and with the older
charts. Students can then determine the prevailing winds that
created the current and identify whether it is part of a larger
gyre in the Atlantic Ocean.
7. Review main points and clarify student questions (2 min/44 min)
8. Closing Statement (1 min/45 min)
Surface currents are one of the three types of currents that
churn the oceans. The most powerful of the surface currents,
and the one that affects us, is the Gulf Stream. That powerful
"river" within the ocean changes the climate, affects
the storms, and moves ships along its entire path.
Analysis
1. What is the correlation between prevailing winds and ocean circulation?
2. Identify three warm water and three cold-water currents in the Northern Hemisphere.
3. What similarities can you draw between warm water currents?
4. What similarities can you draw between cold water currents?
5. In looking at your map, identify the route that one would take from South Portland, Maine to England. Explain your answer.
6. In looking at your map why does Maine not receive the warmer weather benefits of the Gulf Stream?
7. Georges Bank is in the path of the cold water Labrador Current. Hypothesize why Georges Bank was/ has such great fishing.
Analysis Answers
1. Surface currents are created by the global prevailing winds. There is a direct correlation.
2. Warm water currents: North & South Equatorial, Gulf
Stream, North Atlantic, North Pacific, Kuroshio.
Cold water currents: Canary, Labrador, East Greenland, California,
Oyashio.
3. Warm water currents begin in the equator. In the northern Hemisphere all the warm water currents are turn clockwise. This is due to the Coriolis effect and the rotation of the earth.
4. Cold water currents are coming from the poles towards the equator.
5. One would want to follow the Gulf Stream, thus travel in a general north west direction.
6. There is a cold water current that runs south between the Gulf Stream and the coast. Therefore we do not receive the warm air from the gulf stream.
7. Cold water carries with it a lot of nutrients from near the bottom of the ocean. Fish thrive on these nutrients that are carried towards the surface at Georges Bank.
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