1. Challenge – Do all kinds of earth materials erode in the same way? Activity 31 – Resistance to Erosion

2. Getting Started Work with a partner to brainstorm a list of factors that could influence how much of a given earth material (e.g., rock, soil) will be eroded? o The amount of time the earth material is eroded. o The force with which the eroding agent hits the earth material. o The volume (i.e., size) of the eroding agent. o The volume (i.e., size) of the earth material. o The mass (i.e., size) of the earth material. o The composition of the earth material.

3. Introduction Read the introduction on page 35. Copy the following sentences in your journal... Some materials are more resistant to erosion than other materials. If exposed to the same agent of erosion (e.g., a river), the more resistant materials will erode less than other materials.

4. Important Terms Variable – a factor that could have any number of possible values depending on the situation. Controlled Variable – a variable that is either held constant (i.e., did not change) or whose impact is removed in order to analyze the relationship between other variables without interference Tested Variable – a variable that is changed in a systematic way in order to determine its effect Uncontrolled Variable – a variable that is neither controlled nor tested

5. Important Terms: Examples Controlled variables... o force of water o amount of water delivered o landform shape o volume of the earth material Tested variable = type of earth material Uncontrolled variables... o temperature o mass of the earth material

6. Record in Journal Basin Observations Erosion Ranking Water Run-off Ranking 1 2 3 Observation of Erosion Resistance Data Table:

7. Procedure Read steps #1-10 on pages 36-37. Make sure ALL group members understand what to do at each step. HINT: If you are having trouble initiating “rain” from the rainmaker, gently tap the side of the rainmaker or run your fingernail along the bottom of the rainmaker. IMPORTANT: The earth material must remain in the basins when you finish. You will CAREFULLY dispose of the water in the sink without dumping any of the earth material. FOCUS on the effect the water has on the different earth materials, including the material washed into the basin.

8. Analysis Questions Answer questions #1-4 on page 38. All answers should be written in your journal.

9. Analysis Answers (#1) 1A. The models used were like a real landform because the models were hill-like in shape and the water was delivered in a manner similar to rain drops. 1B. The models were not like a real landform because the earth materials did not reflect the variety of materials found in rock and soil; the earth materials were less compact than they would be in nature; and, the it “rained” for a shorted duration and with less force than in nature.

10. Analysis Answers (#2) 2A. The controlled variables were... o force of water o amount of water delivered o landform shape o volume of the earth material o overflow space 2B. The tested variable was the composition of the earth material. 2C. Uncontrolled variables included... o temperature o mass of the earth material

11. Analysis Answers (#3) 3. The material in Basin A eroded less than the other two earth materials. This may be because there was less water running off the material. The material absorbed spring water instead of letting it flow over the hill. Less water flowing down the hill means less material is carried away.

12. Analysis Answers (#4) 4A. Loose soil describes earth material B because it is looser and softer than the other earth materials. 4B. Sticky soil describes earth material A because it is more compact and clumps together more than earth material B. Earth material A also eroded less than earth material B. 4C. Loose soil with vegetation describes earth material C because it eroded more than A, but less than B. There was little run-off because the soil was held in place by components that absorbed water (i.e., vegetation).