Physical Rock Erosion by Plants

Rock Erosion by Plants

Erosion is the wearing away of soil and rock, and the down-slope movement of soil and rock. Some factors that influence erosion include gravity, glaciers, water, wind, ice, and waves.

In this investigation, your students will determine if rocks are eroded by plants.

Rock Erosion and Plants

When plants grow in soil-filled cracks of rocks, their roots may push on the sides of the crack, widening it and eventually breaking the rock apart.

Materials:

• milk carton or similar disposable container

• scissors

• plaster of paris

• bean seeds

Procedure:

1. Cut the top off of a milk carton to form a container about 2½ inches high.
2. Prepare plaster of paris according to directions and fill the container.
3. Push a bean seed that has been soaked in water just under the surface of the plaster and observe for several days.
4. Students describe what they observe.

Questions For Students:

• What would happen if the beans were in the crack of a rock?

• What if they were the seeds of a tree, rather than a bean plant?

• Can plants break apart rocks?

• What type of erosion was caused by the beans?

Science Behind this Investigation

When plants grow in cracks in rocks, their growing roots may produce enough force to break the rock.