Plate Tectonics

Phyllis J. Robinson            Mount Vernon Elementary School
                               10540 South Morgan
                               Chicago IL 60643
                               (312) 535 2825

Objectives:

After this experience the students should
1. be able to identify the three main parts of the earth
2. be aware that the earth's crust is made up of pieces called plates
3. be able to state the theory of Plate Tectonics
4. be aware that convection currents could cause the earth's crustal plates to 
   move
5. be able to identify plate divergence as a possible explanation of Continental 
   Drift, seafloor spreading, and volcanic activity near the Mid Atlantic Ridge
6. be able to identify plate convergence as a possible explanation of 
   earthquakes, volcanoes, mountain building, subduction and the rock cycle.

Materials needed:

1. One chart showing the three main parts of the earth
2. A boiled egg and a plastic knife for each group of five students
3. A puzzle showing the large plates of the earth (one per student)
4. A hot plate, aluminum cake pan, water,and balsa wood pieces. (one set)
5. A 750 ml beaker, a pill bottle, two-hole rubber stopper to fit the pill 
   bottle, glass rods, hot water, cold water, two pennies, and food color (one
   set per group of five students)
6. A sheet of butcher paper 2 m long, 2 demonstration tables, a silhouette of 
   Africa and South America, a marking pen (one set up per class)
7. 2 damp wash cloths per group, 4 popsicle sticks per student, a lump 
   of clay for each student
8. A shoe box, small garbage bag, scissors, newspaper, two boards (30cm X 30cm 
   X 5cm), five pounds of sand, water to dampen the sand
    
Strategy:
  
Activity I 
Show students the core, mantle, and crust of the earth using a chart.  Pass a 
boiled egg and a plastic knife to each group of two.  Have one of the students 
cut the egg in half.  Each person gets half of the egg and will use it as a 
model to discover the three main parts of the earth.  Tell the students that the  
cracked shells represent the part of the crust called plates.                  

Activity II  
Pass a jigsaw puzzle to each student and instruct them to put it together. 
Students should discover that the puzzle represents the earth's crustal plates. 
They should identify the continents and oceans.  They should observe that some 
plates are composed of all continent, all ocean, and a combination of both.  
Introduce terms by having students move two adjacent plates apart (Divergence); 
move two plates together (Convergence); and move two plates so that one moves up 
and the other down with the pieces rubbing past each other (Transformation). 

Activity III
Tell the students the theory of Plate Tectonics. 
The earth's crust is composed of seven or eight major plates and several smaller 
ones.  These plates move. 

Activity IV
Let students relate science equipment to the earth's model.  Hot plate - core, 
water (in an aluminum pan) - mantle, balsa wood chips - crustal plates.  Heat 
the water to boiling.  Put chips in the center of the pan.  Students should 
identify the boiling water as a convection current that causes the balsa wood 
chips (crustal plates) to move. 

Activity V
Each group of four students will get a 750 ml beaker filled with cold water.  
They will fill a pill bottle with hot water, 3 drops of food color and two 
pennies to keep it from floating.  They will cut 2 pieces of glass tubing 8 cm 
long (straws can be substituted for the glass tubing).  Insert a tube into each 
hole of a two hole rubber stopper and position the tubes so that one sticks out 
of the stopper more than the other.  Insert the rubber stopper into the pill 
bottle.  Wipe any colored water off of the bottle.  Hold it by the rim and lower 
the pill bottle into the center of the beaker of cold water until it sits on the 
bottom of the beaker.  Keep the pill bottle upright.  Students should discover 
that this is a convection current and the colored water looks like lava coming 
from a volcano. 

Activity VI
Students will observe a model of diverging plates.  The teacher will push two 
display tables together leaving a small space between them.  She will tell the 
students that the tables represent two Atlantic Ocean plates and the opening 
represents the Mid-Atlantic Ridge.  The teacher will cut off butcher paper two 
meters long and slide it through the opening (Mid-Atlantic Ridge) so that 5cm of 
paper is showing on the surface of each table on each side of the ridge.  Have 
two students each label their paper lava/new crust and mark it with a ruler and 
pen.  Have the student helpers pull out 5cm more of butcher paper and mark it 
lava/new crust.  Have them also tape a silhouette of South America on the left 
crust and Africa on the right crust.  Have helpers pull out 5cm more of butcher 
paper and mark it as before.  Continue the previous steps until the students are 
able to discover that the seafloor is spreading because new crust is being 
added.  The Atlantic Ocean is getting larger.  The continents are moving apart. 
Volcanoes are forming volcanic mountains and islands along the Mid-Atlantic 
Ridge.  The Atlantic crustal plates are moving apart. (Divergence)  

Activity VII 
Students should discover that while the Atlantic plates are diverging, the 
Pacific plates are converging.  Ten students will be Pacific crust.  They will 
hold hands to form a circle to define the size of the earth.  Drop hands.  Ten 
more students will represent the new Atlantic crust.   They will join the 
earth's circle two at a time at the same place.  They will diverge and push the 
Pacific plates closer together (converge).  As more and more new Atlantic crust 
join the line, some of the Pacific plates will move in front of the other 
Pacific crustal plates to make room. (This represents subduction).  Students 
should discover that as the new Atlantic crust diverged the Pacific crust 
converged.  They should discover that the Pacific crust made room for the new 
crust by moving out of the way through subduction. 

Activity VIII
Teacher will explain terms subduction, Asthenosphere, and rock cycle.

Activity IX
Students should be told that continental crust does not subduct into the 
Asthenosphere.   Students will use two damp wash cloths to represent continental 
crust.  They will diverge them and discover that volcanoes could develop between 
the plates.  They will converge (push together) the continental crust.  They 
should discover that the rolls and the folds look like mountains.  Use popsicle 
sticks to form anticlines and synclines.  Students should discover that pressure 
which forms mountains and valleys also causes breaks called faults and sudden 
movements called earthquakes.  Use clay to form various mountain forms.     

Activity X
Use a Fault Box to observe a model of an earthquake.  Cut the bottom of a shoe 
box with scissors.  Cut a small garbage bag so that it will hang down through 
the bottom of the shoe box by about l0 cm.   Attach the bag to the side of the 
shoe box.  Cover the area with newspaper.  Place two boards (30cm X 30cm X 5cm) 
on the newspaper side by side.  Place the shoe box on the crack between the 
board so that half of the box is on each side.  Pull up the garbage bag so that 
it forms the bottom of the shoe box.  Fill the box with wet sand.  Pack it down 
and smooth it out.  Have a helper hold the box steady.  Have students come up in 
groups of four or five.  Let them observe what happens when one of the boards 
slides out from under the fault box.  Return the board and smooth the sand. 
Slide both boards apart until they are separated 15cm.  Do not pull boards all 
the way out.  Return the boards and smooth the sand.  Slide both boards apart 
and push back together.  Return the boards and smooth the sand.  Slide both 
boards alternately up and down, back and forth so that the sides rub against 
each other.  Observe results after each trial.    
  
Bibliography:

Fariel, Robert, Earth Science (teacher's edition) Menlo Park, California, Addison 
Wesley Publishing Co. l984 p 502 (Simulating seafloor spreading)    

Tillery, Bill W. Earth Science Teacher's Resource Binder Lexington, Mass. D.C. 
Heath and Co. l987 (Convection currents-Chapter l5 Lab A p. 56) (Fault box Chap. 
l6 Lab. B p.62) 

Wynn, Douglas E. Focus on Earth Science Teacher Resource Book, Columbus, Ohio, 
Charles E. Merrill Publishing, l988 (Crustal Plates - Teaching Master l6-l) 
(Types of Plate boundaries - Teaching Master l6-2)