Download The Mid-Atlantic Ridge and Geomagnetism

Lesson Plan – Clinic 1
Chris Beatty, Marq Reeher, Kirsten Miller
The Mid-Atlantic Ridge and Geomagnetism
Chris Beatty
Marq Reeher
Kirsten Miller
[email protected]
[email protected]
[email protected]
Topic:
This is a lesson on the mechanics of oceanic ridges, simple plate tectonics, and
geomagnetism designed for grade levels 6-8.
Education Standards:
National:
Science as Inquiry
Students must think critically and logically to make the relationships between
evidence and explanations
Earth and Space Science - Content Standard D
As a result of their activities in grades 5-8, all students should develop an
understanding of:
• The solid earth is layered with a lithosphere; hot, convecting mantle; and
dense, metallic core.
• Lithospheric plates on the scales of continents and oceans constantly
move at rates of centimeters per year in response to movements in the
mantle. Major geological events, such as earthquakes, volcanic eruptions,
and mountain building, result from these plate motions.
• Land forms are the result of a combination of constructive and
destructive forces. Constructive forces include crustal deformation,
volcanic eruption, and deposition of sediment, while destructive forces
include weathering and erosion.
State:
3.2.7 - Inquiry and Design
A) Explain and apply scientific and technological knowledge, mainly explaining
how new information may change existing theories and practice
B) Apply process knowledge to make and interpret observations
C) Identify and use the elements of scientific inquiry to solve problems
3.5.7 – Earth Sciences
A) Describe earth features and processes, mainly those describing the major
layers of the earth and the processes involved in the creation of geologic features.
Students should also recognize that the processes seen today are similar to the
processes that occurred in the past.
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Lesson Plan – Clinic 1
Chris Beatty, Marq Reeher, Kirsten Miller
Instructional Objectives:
Students should be able to:
1) Explain what’s happening at the Mid-Atlantic Ridge
2) Understand how reversing polarity of Earth can be seen in rock formations
Materials, Equipment & Set-up:
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Apple Computer
Data Probe w/ USB connector
Compasses
Magnetometer
Several Magnets
Play Dough
Poster Board
Diagrams
A model of an ocean will be set up, with its sea floor having varying magnetic polarity,
mimicking the Mid-Atlantic Ridge and its surroundings. Students should gain an
understanding for how scientists studying the sea floor were able to come to the
realization that not only does the Earth’s magnetic field change every so often, but that it
is ‘recorded’ in newly formed rock throughout history.
Set-up:
1) Draw a line down the center of the poster paper.
2) Using the play-doh create a “mid ocean ridge” on top of the paper.
3) Place 4 bar magnets end to end in the order of N-S, S-N, N-S, S-N. Make sure that the
two magnets nearest to the ridge have approximately the same magnetic field strength
4) Place the poster paper with play-doh over the magnets with the middle of the “mid
ocean ridge” over the center of the play-doh.
5) Draw a line using your finger or other object to indicate where the line of magnets is
located beneath the poster paper.
Lesson Body:
Engagement: (~5 minutes)
Show the students a compass. Ask the students if they have ever used one before and if
they know where it points. Hold one of the magnets up to the compass and observe how it
reacts. Ask the students what this means for the Earth. Other questions to ponder:
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Is Earth’s surface static? What about under the oceans? What’s going on there?
Why does the Earth’s surface move? Is the planet growing?
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Lesson Plan – Clinic 1
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Chris Beatty, Marq Reeher, Kirsten Miller
How do compasses work? Why do compasses point to north? Is this the North
Pole that it points to?
What would happen if I took my compass to another planet?
Exploration: (~8 minutes)
Guiding Question: Why does polarity vary around a mid-ocean ridge?
Students will conduct a lab in which they map out the polarity of a model sea floor using
the changing magnetic fields of the sea floor as a guide. Using magnetometers, the
students will assess the sea surface floor by noting where polarity shifts. Students will
need an introduction to magnets and the magnetometers before the experiment can begin.
We will tell students that our model is a replica of an ocean that has a ridge in the middle.
When the students see that the sea floor has alternating polarity they should begin asking
themselves why this may be. They will have already been taught that the sea floor is
slowly spreading apart about the Mid-Atlantic Ridge and that new earth is continually
being created here. After a bit of guidance they will deduce that the Earth’s polarity must
change every so often.
Explanation: (~3 minutes)
By relating what the students are doing in the experiment to what scientists did during
their experiments in which they found that their compasses were acting weird, the
children will gain a deeper grasp of how what they are doing relates to the real world.
The physics behind what is going on is too complicated for most of these children, so just
a basic explanation of magnets, plate tectonics and the fact that Earth’s surface is
constantly changing about the Mid-Atlantic Ridge is needed. The students will relate the
fact that new earth is constantly being created at the ridge, and that this new earth will in
time be spread out from the ridge. Because the newly formed rock holds the polarity of
the Earth, and the polarity changes about the ridge, the only explanation is that Earth’s
polarity must change over time.
Evaluation: (~2 minutes)
The lab activity will allow the evaluation and explanation parts of the lesson to go hand
in hand. The lab will make the ideas taught to them clearer by giving the students a
hands-on activity where they analyze the data in real time. By doing the activity, rather
than just hearing about it, they will gain a clearer understanding of the alternating polarity
of the ocean floor about the Mid-Atlantic Ridge. We will be able to evaluate the students’
learning progress by asking a few simple questions both during and after the lab. For
example, once the students realize that the polarity is changing under the model ocean
floor, they will likely begin to talk about this, and we can question them what must be
under the sea floor making the polarity change. This will also facilitate questioning about
the features of the sea floor, and how it related to an actual sea floor. If they understand
where the ridge is located, and why the magnetic fields are symmetric on either side, then
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Lesson Plan – Clinic 1
Chris Beatty, Marq Reeher, Kirsten Miller
they understand the concept of Earth’s shifting polarity, and also that the crust is
separating at the ridge. Further evaluation can be conducted by giving the children
thought experiments via several alternative scenarios to test their knowledge.
Furthermore, a short activity will be provided to the students where they will explain
what would happen in these alternative scenarios.
Elaboration: (~2 minutes)
Time permitting; discussion can be furthered to cover topics such as:
• Subduction zones preventing the Earth from getting larger
• Magnetic fields of other planets and how they compare to Earth’s magnetic field
• Discussion relating to compasses and what would happen to a compass when the
Earth’s polarity reverses
• How fossil records can be used to back up theory
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