Download Plate Tectonics: What Happens when Plates Collide

Kathleen Moburg
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Author: Kathleen Moburg
Title of Lesson: Plate Tectonics: What Happens when Plates Collide?
Subject Area(s) 10th grade General Science; Earth Science Unit
Description of lesson (one or two sentences) Students will investigate the
movement of plates and their resulting land forms by using Graham crackers.
Length of lesson(s) one 50-minute period. Students have already seen a video on
plate tectonics, have studied the mechanism of convection, conduction; learned the
names and locations of major plates, mountain ridges.
Student Objectives: To visualize how various land features (mountains, faults,
ridges) form as a result of plate movement through modeling four types of plate
boundaries
Materials (per group of four) 1 Graham cracker per person (entire “block”);
One Paper towel/person (keep cracker off the table);
1 wide-mouth cup with water (to be used to dip the edges of crackers in);
canned frosting (one can will be adequate for class of 24) - approximately one
tablespoon per student.
World Map showing the plates (one per person)
Worksheet describing the types of movement “Plate Tectonic Movements and
Landforms”
Procedure/Steps of Lesson
1. Students review the worksheet “Plate Tectonic Movement and Landforms”.
They will write the names of each plate in the appropriate spot. Also, students will draw
arrows showing the direction of plate movement.
2. Using a textbook/map students draw and label the mountain ranges, subduction
zones and mid-ocean ridges on the map.
3. To demonstrate how fault lines occur do the following with the graham
crackers
4. Break the large rectangle of Graham cracker
along the perforated line into two equal –sized pieces.
5. Place the two pieces together again along
the broken edges
6. Slide the two pieces in opposite directionsone upward, the other downward.
Question A. What observations can you make about sliding these past one another?
Hint: do they slide easily?
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B) Do you notice “crumbs”? What do the crumbs represent in real fault lines?
C) What kind of boundary does this motion represent? (look at the diagram below)
D) On the world map, where would this type of movement occur? Show this place on
the map by drawing in yellow triangles.
7. Try another movement: place both crackers
on the paper towel. Put the edge of one cracker
on top of the edge of the other. It should look
like this.
8. Slide one over the other.
E. What do you observe when
two “collide”?
F. Look at the diagram on the right.
Which type of boundary does this
represent?
G. Where on the world map would this type of fault occur? On the map use GREEN
CIRCLES to indicate where this event occurs.
H. What type of landform develops at this type of boundary?
Try another plate boundary.
9. Dip one edge (about ¼ inch) of both crackers into the water so that they are slightly
damp. Do not get them soggy!
10. Place the two wet edges together and
slowly push them towards each other.
I.
What do you observe when the two wet
edges get pushed together?
Kathleen Moburg
J. What type of boundary does this represent?
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K. What kind of landform occurs at this boundary?
L. Draw RED SQUARES on the world map to show where this occurs.
Try another boundary.
11. Put a tablespoon-sized glob of frosting on ONE
of the two crackers
12. Using the other cracker, break it in half
13. Place the two newly- broken pieces on top
of the bottom cracker with frosting. It should
look like a sandwich. Make sure that the top
pieces are touching
14. Push down on both top pieces at the same time
that you pull them apart.
M. What do you observe (with the frosting) when you pushed and pulled the top
crackers apart?
N. What type of plate boundary does this represent?
O. What type of landform occurs at this type of boundary?
P. On the world map, use a BLUE LINE to show where this occurs
Scientific Explanation(s) to clarify Lesson
]
Kathleen Moburg
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Explanation.
As the 12 major plates of the earth’s crust move due to the convection of heated
magma in the mantle, this causes many events.
Where two plates slide past one another laterally enormous amounts of
built up pressure is released in the form of earthquakes. This is illustrated
by the TRANSFORM fault above. The side-to-side movement causes a
great deal of friction.
The diagram above labeled “Extensional” is more often called “divergent”
boundaries. This occurs when two plates are pulling away from each
other. The plates are thought to pull apart because of the upwelling of
the heat from the convection current in the mantle below the two plates.
As the upwelling magma rises, it strikes the bottom of the plates, and
pulls the two plates apart. In the void left by the two plates parting, magma wells up in
its place. This is best illustrated in the Mid-Atlantic ridge. This is also called Sea-Floor
Spreading.
A third type of plate movement is compressional or convergent boundaries. As the
name suggests, the plates are pushing together. This movement is like a slow-motion
car crash. When two plates collide (at a convergent plate boundary), some crust is
destroyed in the impact. Depending on what types of plates are involved different
results occur.
Oceanic Plate and Continental Plate - When a thin oceanic plate collides with a thick
continental plate, the denser oceanic plate is forced under the continental plate. This
type of event is called subduction. This occurs along the west edge of South America
where the Pacific plate is being pushed under the S. American plate. This forces the
continent to rise, forming the Andes Mountains. The type of rock formed is andesite,
hence the name “Andes”.
Two Oceanic Plates - When two oceanic plates collide, one may be pushed under the
other and magma from the mantle rises, forming volcanoes in the vicinity.
Two Continental Plates - When two continental plates collide, mountain ranges are
created as the colliding crust is compressed and pushed upwards and rocks
metamorphose under the pressure. An example is the Himalayan Mountain range
Kathleen Moburg
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Extensions: Computer lab
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/continents/shtml