Modeling Erosion
Moving water is the major cause of erosion on Earth. In this lab, you will investigate some factors that affect the rate of erosion by moving water.
Problem What are some of the factors that affect the rate of water erosion?
Materials
metric ruler
large sheet of cardboard
plastic wrap
newspaper
soil
blocks
pencil
paper cup
scissors
drinking straw
modeling clay
paper towels
small rocks
Skills Using Models, Inferring
Procedure
On a separate sheet of paper, make a data table with 4 columns and 4 rows. Label the columns Elevation of Cardboard, Slope of Cardboard, Rocks, and Observations.
Measure and record the length of the cardboard in centimeters. Wrap the cardboard with plastic wrap to keep it dry.
Put several sheets of newspaper on a flat surface. Place cardboard on the newspaper and spread a thin layer of soil over the cardboard.
To model a hillside, raise one end of the cardboard about 5 cm from the flat surface by placing blocks under one end.
Using a pencil, make a hole in a paper cup 1 cm from the bottom.
Cut the straw in half with the scissors and insert the end of one of the halves 2 cm into the hole in the cup.
Use modeling clay to seal the hole around the straw. Make sure that the clay forms a tight seal around the straw.
Place the cup in the middle of the raised end of the cardboard, so that the straw is pointing downhill as shown.
Place your finger over the straw's opening as another student fills the cup with water.
Remove your finger. Record your observations in your data table.
Clean the cardboard with paper towels and cover it again with soil. Put used soil in the trash.
Now use blocks to raise the end of the cardboard 15 cm above the flat surface. Repeat Steps 8 through 11.
Lower the end of the cardboard to 5 cm above the flat surface. Repeat Steps 8 through 11 again, but this time place a small rock on the cardboard directly in front of the straw. In your data table, record your observations about how water moves around the rock.
Repeat Step 13, but this time place a pile of several small rocks on the cardboard directly in front of the straw. In your data table, record your observations about how water moves around the rocks.
Analyze and Conclude
Observing Does water erosion create smooth curves or sharp angles?
Analyzing Data How did increasing the elevation of the cardboard affect the speed of the water?
Calculating The slope of a hillside is equal to its height divided by the horizontal distance it covers. Using the length of the table under the cardboard and the height it was raised, calculate and record the slope of the model hillside in each row of your data table.
Inferring What is the relationship between the slope of a hillside and the rate of erosion?
Analyzing Data Compare the movement of the water with one rock and several rocks in front of the straw. Explain any differences you observed.