The Rock Cycle

Problem: How is the Earth’s surface constantly changing?

Objectives: After you have completed this investigation, you should be able to:

  1. Draw and label the rock cycle
  2. Describe the major processes and rock types involved
  3. Compare and contrast the origins of igneous, sedimentary, and metamorphic rocks

Materials:

4 different colored crayons NewspaperPencil Sharpener

Safety gogglesWaxed paperAluminum foil cups (Flinn evaporating

Aluminum foilTextbooksDish, disposable, aluminum AB1263)

Hot plate Tongs (clothespin)

Procedures:

Part I Sediments

  1. Cover your work area with newspaper.
  2. Using the pencil sharpener, shave 4 crayons into shavings. Pile the fragments by color on separate pieces of waxed paper.
  3. What process does this demonstrate?
  4. Wrap the fragments by color in wax paper.

Questions:

  1. Are all the weathered rock fragments in your pile the same size? Explain.
  2. Physical weathering occurs when rock is exposed to water, air, or changes in temperature which cause the rocks to break into smaller pieces. Chemical weathering occurs when the rocks react to form new substances. Which types does your crayon activity represent? Why?

Part II Sedimentary Rock

  1. On a sheet of aluminum foil, drop your rock fragments in the center.
  2. Fold the foil over the fragments into a packet.

Questions:

  1. Erosion is when weathered material is moved. Explain how you are an agent of erosion. Give examples of agents of erosion.
  2. What is deposition?

Lithification and Sedimentary Rocks

  1. Place the foil package between two textbooks, then, stand on them for about a minute.
  2. Remove the foil from between the textbooks and open the foil. Examine the sedimentary rock.
  3. Remove a small piece from the sedimentary rock.

Questions:

  1. Describe the thickness of the crayon sediments in the foil before and after you squeezed them by standing on them.
  2. What happened to the spaces between the crayon sediments?
  3. Compaction occurs when pressure squeezes out the air spaces between the sediments.

Cementation “glues” the sediments together. Does the activity done here represent compaction or cementation or both? Explain your answer.

Part III Metamorphism and Metamorphic Rocks

  1. Place the foil between two textbooks, then, stand on them.
  2. Briefly place the foil package on a hot plate at low temperature.
  3. Repeat steps 1 and 2 an additional three times. Use the clothespin to move the package.
  4. Place the package on the lab bench and allow it to cool.

Questions:

  1. Predict: How is the color-layer thickness different between the sedimentary rock and the metamorphic rock?
  2. Predict: How did the crayon fragments change? Why did this change happen?
  1. Once the package is cool, open it and examine the newly formed ‘metamorphic rock’.
  2. Place part of the metamorphic rock in an aluminum evaporating dish. Make sure to keep the remaining metamorphic rock and the previously saved sedimentary rock in a safe place.

Part IV Igneous Rocks

  1. Place the aluminum evaporating dish on the hot plate
  2. Adjust the hot plate’s temperature until the rock has melted.
  3. Turn off the hot plate and allow the rock to cool.
  4. Compare the three different types of rocks you made.

Questions:

  1. What happened to the crayon ‘rock’ fragments when they were heated on the hot plate?
  2. How does the igneous crayon rock differ from the sedimentary and metamorphic rocks?
  3. Which of the three types of rock is the easiest to break apart? Why do you think this is? (Think about how the rock was formed.)