Laboratory Title: Mid-Atlantic Ridge, and Magnetic Polarity Reversal
Your Name: Amy Garrison
Concept(s) Addressed:
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Earth Science
o Plate Tectonics
o Divergent boundaries
o Mid-Atlantic Ridge
Physics
o Magnetism
o Magnetic Polarity Reversal
Lab Goals: Students will be able to identify where the mid-Atlantic Ridge is, and become
familiar with how it was formed. Students will learn about magnetic polarity reversal, and how
the mid-Atlantic Ridge is important to this topic.
Lab Objectives: Students will:
 discover where the mid-Atlantic Ridge is located, as well as what it is.
 learn about magnetic polarity reversal, how this is verified and how the mid-Atlantic
Ridge is related to this subject.
 experiment with magnets, learn about magnetic poles, and observe what happens when
like poles come together as well as when opposite poles come together.
 observe what happens when a compass is placed near a magnet.
Science Benchmark(s) Addressed:
Grade 4
4.2
Interaction and Change: Living and non-living things undergo changes that
involve force and energy.
4.2P.1 Describe physical changes in matter and explain how they occur.
4.2E.1 Compare and contrast the changes in the surface of Earth that are due to slow and
rapid processes.
4.3
Scientific Inquiry: Scientific inquiry is a process of investigation through
questioning, collecting, describing, and examining evidence to explain
natural phenomena and artifacts.
4.3S.3 Explain that scientific claims about the natural world use evidence that can be
confirmed and support a logical argument.
Grade 5
5.2
Interaction and Change: Force, energy, matter, and organisms interact within
living and non-living systems.
5.2P.1 Describe how friction, gravity, and magnetic forces affect objects on or near
Earth.
5.3
Scientific Inquiry: Scientific inquiry is a process of investigation based on
science principles and questioning, collecting, describing, and examining
evidence to explain natural phenomena and artifacts.
5.3S.2 Identify patterns in data that support a reasonable explanation for the results of an
investigation or experiment and communicate findings using graphs, charts, maps,
models, and oral and written reports.
Materials and Costs:
List the equipment and non-consumable material and estimated cost of each
Item ..........................................................................................................................$
PowerPoint slide presentation ............................................................................ Free
12 bar magnets, poles marked with North and South ...........................................10.95
Lakeshore Products
http://www.lakeshorelearning.com/product/productDetBySkuCode.jsp?product_code=LA657
36 bar magnets ......................................................................................................29.95
Lakeshore Products
http://www.lakeshorelearning.com/product/productDetBySkuCode.jsp?product_code=LA657
12 compasses ..........................................................................................................4.20
Windy City Novelties, Inc.
http://www.windycitynovelties.com/13846p/1-and-a-half-inch-magnetic-compasses.html?s_cid=FRO13846
Assorted magnets, circular magnets 8/package @ 2.49 x 2 packages .....................4.98
Michael’s Craft Store
Assorted magnets, Bag of Magnets 30/bag @ 5.95 x 2 packages .........................11.90
Edmund Scientifics
http://scientificsonline.com/product.asp_Q_pn_E_3082265
Matchbox cars, 20 car set @ $19.99 x 1 ................................................................19.99
Estimated total, one-time, start-up cost for equipment: .......................................$81.97
List the consumable supplies and estimated cost for presenting to a class of 30 students
Item ..........................................................................................................................$
2 pencils (round not octagonal sided) per group 12/package @$1.50 x 3 ...............4.50
Paper and copies of handouts, school supplies .................................................. Free
Rubber bands, bag @4.59 x 1 ..................................................................................4.59
Estimated total, consumable costs: ........................................................................$9.09
Time:
Preparation time: 30-60 minutes – to order online supplies and gather in town supplies
Instruction time: 30 - 60 minute lesson
Clean-up time:
15 minutes
Background:
The students really need to have some kind of idea of what plate tectonics is, before learning
about the mid-Atlantic Ridge. On my pps, slides 3 – 8, I have some information and several
pictures on plate tectonics. Some good websites for information on this subject are:
http://www.pbs.org/wgbh/aso/tryit/tectonics/intro.html
http://www.wisegeek.com/what-is-plate-tectonics.htm
http://www.extremescience.com/PlateTectonicsmap.htm
http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html
It is also helpful to discuss the 3 different kinds of plate boundaries, and to point out that the
mid-Atlantic Ridge is a divergent plate boundary. My pps slides #5 and 6 show images of
divergent plate boundaries, and talk about what that is (Slide 5 also shows convergent and
transform boundaries.)
I think one of the coolest facts about the mid-Atlantic Ridge is that it is the longest mountain
range in the world, (- something you don’t usually learn in school.) It is a mid-ocean ridge that is
located along the floor of the Atlantic Ocean, and it separates the Eurasian Plate from the North
American Plate in the North Atlantic, and the African Plate from the South American Plate in the
South Atlantic. The mid ocean ridge systems are the largest geological features on the planet.
The Mid-Atlantic Ridge extends from a junction with the Mid-Arctic Ridge, northeast of
Greenland southward, to the Bouvet Triple Junction in the South Atlantic. These plates are still
moving apart, so the Atlantic is growing at the ridge at a rate of about 2.5cm per year, in an eastwest direction. A notable feature along the ridge is a deep rift valley that runs along the axis of
the ridge for nearly its entire length. This rift marks the actual boundary between the bordering
tectonic plates, and it is where magma from the mantle reaches the seafloor, erupts lava, and
produces new crustal material for the plates.
The ridge was discovered in the 1950s. Its discovery led to the theory of seafloor spreading and
general acceptance of Wegener's theory of continental drift. Most of the ridge system is under
water but forms land as a set of volcanic islands of varying size that run the length of the Atlantic
Ocean. These islands are:
1. Jan Mayen (Norway)
2. Iceland
3. Azores (Portugal)
4. St Paul’s rock (Brazil)
5. Ascension Island (UK)
6. St Helena (UK)
7. Tristan da Cunha (UK)
8. Gough Island (UK)
9. Bouvet Island (Norway)
http://en.wikipedia.org/wiki/Mid-Atlantic_Ridge
About every half million, years or so, the Earth’s magnetic polarity reverses. - So does the
magnetization of the ocean floor. When magnetic reversals happen, molten lava emerges from a
volcano and solidifies to a rock. In most cases it is a black rock known as basalt, which is faintly
magnetic, (like iron emerging from a melt.) Its magnetization is in the direction of the local
magnetic force at the time when it cools down.
Instruments can measure the magnetization of basalt. If a volcano has produced many lava flows
over a past period, scientists can analyze the magnetizations of the various flows and from them
get an idea on how the direction of the local Earth's field varied in the past. This procedure
suggested that times existed when the magnetization had the opposite direction from today's
direction. All sorts of explanation were proposed, but in the end the only one that passed all tests
was that in the distant past, the magnetic polarity of the Earth was sometimes reversed.
In the ocean floor the magnetization was orderly, arranged in long strips. The strips on the
Atlantic ocean floor, in particular, all seemed parallel to the "mid-Atlantic ridge." The ridge is
marked by the focus-points of earthquakes and by some volcanic islands. More recently it was
explored by research submarines, which have at times observed lava oozing out at its crest.
Not only were the magnetic strips lined-up with the central ridge, but their structure and
distribution seemed remarkably symmetric on both sides: if a narrow-wide pair of strips was
observed at a certain distance east of the ridge, its mirror image was also found at about the same
distance to the west. It was proposed that the sea floor was in constant motion, pulling away
from the central ridge at a rate of about one inch (2.5 cm) per year.
As the "plates" on each side are pulled away, lava emerges from the middle, solidifies and
"records" the prevailing magnetic field. The newly formed basalt sticks to the plates and is also
pulled away--some of it towards Europe and Africa, some towards America. Every half million
years, on the average, the Earth's magnetic polarity reverses, and so does the magnetization of
the ocean floor. Each strip represents an epoch of one or the other magnetic polarity, and the
symmetry is also explained. It is as if the sea-floor was a giant tape recorder, with twin tapes
emerging from the mid-Atlantic ridge, recording the Earth's magnetism at the time they emerge
and then traveling in opposite directions. Similar magnetic strips were also observed in all other
oceans.
http://www.iki.rssi.ru/mirrors/stern/earthmag/reversal.htm
Procedure:
PowerPoint
The information on the slides was important.
Supplies:
 PowerPoint Lesson (found with this lesson plan)
 Vocabulary words copies
Procedure:
1. Distribute the vocabulary words to your students. Discuss each word and its definition.
2. Part of the slide presentation is interactive. You present slides 1-6.
3. For slide #7 pick a student to read aloud. You present slides 8-11.
4. For slide #12 pick a student to read aloud.
5. For slide #13 pick a student to read aloud. You present slides 14.
6. For slide #15 pick a student to read aloud. You present the remaining slide.
Optional: ask the students to read the slides to themselves, and ask them to write a sentence after
each slide, or at the end of the presentation, ask them to write a paragraph about the information.
Hold a class discussion and talk about what the students wrote down, and what they understand
about what was written on the slides.
Vocabulary Words:
 epoch - The start of a new period of something, in time.
 fissure - A crack or a cleft.
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magnetic Poles - The points in the Arctic and Antarctic toward which the needles of
magnetic compasses point. They are not placed at the geographic poles.
magnetization - The extent or degree to which something is magnetized.
polarity - Simply said: It's POSITIVE and NEGATIVE. The flow of current is from (+)
to (-)
Mutual opposition: a relation between two opposite attributes or tendencies.
symmetry, or symmetric - (mathematics) An attribute of a shape or relation; exact
reflection of form on opposite sides of a dividing line or plane.
Magnetic Poles
Electricity has positive and negative charges. Like charges repel each other and opposites attract.
Let’s see if there is an analogy for magnetism.
Supplies:
 Compass
 bar magnets
 assorted magnets
 2 round pens or pencils
Procedure
Activity 1:
1. The bar magnets are marked with North and South poles. Put the pens under one of the bar
magnets for rollers. Use the other bar magnet to determine if like poles attract or repel.
Record your findings.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
2. Move all of the magnets away from one bar magnet. Put the Compass at the end of the
magnet marked “N”. Draw an arrow on the diagram below showing what direction the
painted end of the compass-needle points. Then repeat for the end marked “S”.
N
S
3. Use the compass in the same way to determine the location of the North and South poles for
each of the other magnets. Draw a sketch of each one and show the poles.
Activity 2:
“Invisible Force” Moving Car
Supplies:
 Two magnets
 One rubber band
 One metal match box car
Procedure:
1. Take one magnet, the metal matchbox car and the rubber band; place the magnet on
top of the metal car by wrapping the rubber band around them.
2. Take the second magnet and hold it behind the metal matchbox car (without touching
the car) and push the car forward without touching the magnet to the car.
Assessment
Quiz:
1. What is the mid-Atlantic Ridge, and where is it located?
2. In what direction(s) is the mid-Atlantic Ridge oriented?
3. In what direction(s) is the mid-Atlantic Ridge spreading?
4. What kind of plate boundary creates the mid-Atlantic Ridge?
5. How much is the Atlantic growing, or spreading each year?
6. What can you tell me about ocean floor magnetism and magnetic reversals?
7. What kinds of magnetic poles attract? Repel?
8. What kind of oceanic, volcanic rock is faintly magnetic ?
9. How often do scientists think the magnetization of the Earth changes?
10. What happens to a compass when it is placed near the North end of a bar magnet? When
placed near the South end?
Great website for kid friendly magnet experiments:
http://www.kids-science-experiments.com/makeneedlemagnets.html
Mid-Atlantic Ridge (& Magnetic Polarity Reversal) Lesson Plan
Sources:
http://en.wikipedia.org/wiki/Mid-Atlantic_Ridge
• http://www.iki.rssi.ru/mirrors/stern/earthmag/reversal.htm
• http://www.wisegeek.com/what-is-plate-tectonics.htm
• http://www.extremescience.com/PlateTectonicsmap.htm
Student Worksheet
Magnitism
Name: ____________________________________________________
The bar magnets are marked with North and South poles. Put the pens
under one of the bar magnets for rollers. Use the other bar magnet to
determine if like poles attract or repel. Record your findings.
_______________________________________________________
_______________________________________________________
_______________________________________________________
_______________________________________________________
Move all of the magnets away from one bar magnet. Put the Compass at
the end of the magnet marked “N”. Draw an arrow on the diagram below
showing what direction the painted end of the compass-needle points.
Then repeat for the end marked “S”.
N
S
Use the compass in the same way to determine the location of the North
and South poles for each of the other magnets. Draw a sketch of each
one and show the poles.