Lesson 4: Plate Tectonics


Strands:

Earth Sciences, Physical Characteristics of Places and Regions

Standard Statements:

3.5.4 A; 3.5.4 B; 7.2.6A; 7.2.6 B

Content Objectives:

For this activity, students will:

1. Demonstrate plate tectonics through a “hands on” experiment.

2. Create a model of sedimentary rock layers of Pennsylvania.

3. Demonstrate the effects of erosion.

4. Describe the correlation between their model and the map of Surficial Materials of Pennsylvania.

5 .Describe the correlation between their model and ridges as shown on the DSR map.

6. Demonstrate the effect of the collisions of tectonic plates on layers of rock.

Assessment Strategies:

Students should answer these two questions during small group or whole class discussions:

“What are the most important things you learned today?”

“Where did our Pennsylvania ridges come from?”

Suggested Level:

Grades 4-6

Standards Category:

  • Science and Technology
  • Geography
     

Materials:

Each student will need:

  • ¼ lb. plasticene for each student (5 different colors needed) and a sheet of waxed paper for each group
  • Quart size Ziploc freezer bags for each student (a few extras may be helpful)
     

Each group will need:

  • Digital Shaded-Relief Map of Pennsylvania (DSR map)
  • Land Cover Map of Pennsylvania (LC map)
  • Map 64 - Surficial Materials of Pennsylvania (available from PaGS)
  • Overlays created in last lesson
  • Marking pens
  • Large paper clip
  • Overheads showing the earth at different stages throughout time (available on the at http://www.scotese.com/earth.htm.
     

Instructional Strategies:

  • Whole class – (may need 2 class periods to complete this lesson.)
  • Cooperative groups
     

Procedure:

This activity will provide the students with a “hands-on” model of the topography of Pennsylvania.  The students will construct layers of earth out of various colors of plasticene to model layering of rock types.  They will distort these layers to model the collision between the continents.  Students will cut away the centers to model erosion of the ridges and observe the different colored layers representing the different layers of rocks.  Students will match this model to the ridges shown on the map of “Surficial Materials of Pennsylvania” and finally to the “Digital Shaded-Relief Map of Pennsylvania.”  (For more information on tectonic plates, see background information.)

1. Distribute the clay so that each group member has a DIFFERENT color of clay. It is best to have a minimum of five colors per group.  Place the clay inside a 1-quart freezer bag.  Take time for the students to flatten the clay so it is as thin as possible.  This will take 15-20 minutes to complete.  Do not remove the clay from the bag until instructed to do so.

2. The teacher should introduce the lesson by reviewing how mountains were made.  Explain that the earth is made of a hot core with solid rock floating on top.  Earthquake zones and volcanoes should be shown on maps.  (NOTE: Two possible websites for background information and illustrations can be found at: http://pubs.usgs.gov/publications/text/zones.html and http://livescience.com/forcesofnature/.

3. Pennsylvania has these zones also. Class discussion should center on how the earth’s plates move and change creating earthquakes or volcanoes. Using overheads showing the earth at different stages throughout time, follow the movement of the continents as we know them.  Pay close attention to the time involved with the movement!  The students must realize this happened over tens of millions of years. As the North American plate moves across the equator, discuss how the climate will change.  As Pennsylvania crosses the equator, this area became a tropical rainforest.  This tropical rainforest became the layer of carbon that was compressed into coal. If the North American plate had not moved across the equator, we would never have had the climatic conditions that eventually produced the coal we now find in Pennsylvania. (For more information about coal formation, see background information.)

4. As you go through the ages illustrated by the overheads, lay down one color of clay at a time building a single “continent” of rock layers.  (This “continent” should be built on top of waxed paper to make the folding of the continent easier.)  Once all the layers of clay have been applied, each group should model the North American continent colliding with the African continent to compress the clay into mountain ridges. Try to create two good ridges in your mountain range.  The students should note that just like the earth, the layers of clay may break.

5. Using a large paper clip (which has been unbent), scoop out the mountain top along one fold to show erosion. This usually happens at fracture points that run perpendicular to the direction of the mountain ridges. It should be deep but as narrow as possible to allow the students to view the different layers of “rock.”  One mountain ridge should be scooped to the lowest color.  The other mountain ridge should not be as deep for comparison.   The students should note that the layers stretch at the top of the ridges and compress at the bottom distorting the layer of rock. As most students think of rock as “unbendable,” they will be surprised to see the effects of pressure.

6. Introduce the students to the “Surficial Features Map” (PaGS Map 64) and discuss how their model is the same as this map.  Discuss the varying colors and their arrangements. How were the layers created?

The student groups should SAVE their model mountains in labeled plastic bags or by wrapping them in wax paper.  They will need them again in activity 6.

CLOSING:  Summarize that our Pennsylvania mountains were created many millions of years ago when our North American Plate collided with the African Plate.  Evidence to support this theory includes the presence of the same rock formations on both continental coasts.  Geologists also know that folded rock layers forming our mountains were originally deposited as sediments on the ocean floor. To further support this theory, we find marine fossils in our folded mountains.