Rock Abrasion

Association of American State Geologists

Activity Source: 

Association of American State Geologists. Adapted with permission.

Rocks break down into smaller pieces through weathering. Rocks and sediment grinding against each other wear away surfaces. This type of weathering is called abrasion, and it happens as wind and water rush over rocks. The rocks become smoother as rough and jagged edges break off. In this activity, you will model how abrasion works.

Materials

For each person:

  • 2-3 sugar cubes
  • 2-3 pieces of gravel, about the same size as the sugar cubes
  • Small plastic container with a lid
  • Magnifying glass
  • Notebook and pen
  • Paper (e.g., newsprint) to cover work surface
    1. Cover your work surface with paper. Look at the sugar cubes with your magnifying glass. Record your observations in your notebook by drawing or writing about the sugar cubes.
    2. Place your sugar cubes in the small plastic container and close the container tightly with the lid. Predict how the sugar cubes will change after they have been shaken inside the container for one minute. Record your predictions.
    3. Shake the container with the sugar cubes inside for one minute. Open your container and pour the contents onto the table. Look again at the sugar cubes. What do you observe?
    4. Now, put the sugar cubes back into the container along with the gravel. Close the containers tightly. Predict how the sugar cubes will change after they have been shaken inside the container with the gravel for one minute. Record your prediction.
    5. Shake the container a second time for 1 minute. Use your magnifying glass to re-examine the sugar cubes. What happened this time, and why?
    6. How long do you think this type of weathering takes? Why? In nature, rock abrasion takes a long time. Your model simulated rock abrasion, but much more quickly!