Objectives: at the End of the Lesson the Students Will Be Able to

Lab: Modeling Plate Boundaries

MATERIALS: For each student group:

 1½ large graham  Wax paper crackers  Cup of water  Frosting  Plastic spoon  2 ceramic tiles (1½ x 1½ inches)

 Paper towels DIRECTIONS: Make the model a. Each group needs wax paper and a spoonful of frosting. Spread frosting into a layer about a cm thick using a spoon on one side of the wax paper. Make sure the other half of the wax paper has no frosting on it. This space will be used later. b. The frosting in this model represents the asthenosphere, the plastic layer on which Earth’s plates ride. The plates in this model are represented by the graham crackers (continental crust) and the tiles (oceanic crust).

1. Model of Diverging Crust a. Place the two tiles (oceanic crust) onto the frosting right next to each other. b. Press down slowly on the tiles (because they are dense and will sink a bit into the asthenosphere) as you slowly push them apart about half a centimeter. c. Notice how the frosting is exposed and pushed up where the plates are separated? This is analogous to how magma comes to the surface where real plates are moving apart at divergent plate boundaries. Most divergent plate boundaries are located within oceanic crust. When plates begin to pull apart at continents, rift valleys are made, like the Great Rift Valley in Africa, which can become the bottom of the sea floor if the plates continue to pull apart. Draw and label a picture of your model. Color the tiles brown and the frosting orange.

Models of Convergent plate boundaries a. Continent - oceanic collision 1. Remove one of the tiles from the frosting. 2. Place one of the graham cracker halves lightly onto the frosting asthenosphere next to the remaining tile. The graham cracker represents continental crust, which is thicker and less dense than oceanic crust (tile). It floats high on the asthenosphere so don't push it down. 3. Gently push the continent (graham cracker) towards the ocean plate (tile) until the two overlap and the graham cracker is on top. The oceanic plate is subducted below the continental one. Draw and label a picture of your model. Tile is brown, graham crackers are green, frosting is orange. b. Continent-continent collision 1. Carefully break a cracker into two pieces. Take the two pieces of graham cracker and dip one end of both crackers into the glass of water for just a few seconds. 2. Place the crackers with wet ends together onto the side of the wax paper without the frosting. 3. Slowly push the graham crackers towards each other. Notice how the wet ends crumple? This is how mountains are made at convergent plate boundaries! When continents move towards each other there is nowhere for the rock to go but up. Draw and label a picture of your model. Color on graham cracker light green and one graham cracker dark green.

3. Transform plate boundaries a. Carefully break a cracker into two pieces. Fit two of the pieces back together side to side. Put one hand on each cracker piece and apply steady and slight pressure as you push them together sliding one away from you while sliding the other one towards you. Describe what happens. Draw and label a picture of your model. Color on graham cracker light green and one graham cracker dark green. 4. Clean up your work area. Wash the tiles with soap and water. 5. Answer the questions in the hand out. Lab: Modeling Plate Boundaries 4. Draw and label a diagram that represents your model of Observations: transform plate boundaries.

1. Draw and label a diagram that represents your model of diverging crust.

Questions:

1. What do the graham crackers represent? 2. Draw and label a diagram that represents your model of converging crust that shows a continent – oceanic collision.

2. What do the ceramic tiles represent?

3. What did the frosting represent? What does the real thing do that the frosting isn’t modeling?

3. Draw and label a diagram that represents your model of converging crust that shows a continent – continent collision. 4. In the first model that you made (step 1), what kind of plate boundary were you demonstrating? What land feature did it form? Where does this kind of plate boundary activity take place? 5. Describe the second model that you have made (step 2). How the pressure is released. Explain how this is similar to the does this relate to the real Earth and where does this happen? situation along the San Andreas Fault. What actually happens to crust material that is subducted? (pushed below crustal material). What could crust material become if it is forced up over the other crust?

6. In what way are the wet crackers more like real crustal plates than the dry crackers? Explain what happened in model 2b (wet crackers) and how it related to what happens on Earth when continental plates meet. Where on earth can we see an example of this kind of plate boundary?

7. In the fourth model (step 3), nothing happens at the beginning, and then as pressure increases, the crackers finally break and