Student Exploration: Erosion Rates

Student Exploration: Erosion Rates [Note to teachers and students: This lesson was designed as a follow-up to the Weathering and River Erosion lessons. We recommend doing those activities before trying this one.] Vocabulary: climate, erosion, precipitation, sandstone, shale, vegetation, valley, weathering Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Erosion is the removal and movement of soil, rocks, and other materials from one place to another on Earth’s surface. What are some forces that might cause erosion to occur? Water, wind, gravity 2. How quickly erosion occurs depends on many factors. In each box of the table below, circle the choice you think would cause erosion to occur more quickly. Hard rocks Soft rocks Lots of rain Little rain Hot weather Cold weather Many plants Few plants Gizmo Warm-up In the River Erosion Gizmo, you learned about the ways that rivers erode soil and change landscapes over time. The Erosion Rates Gizmo models erosion in a simulated 3D landscape. Using the Gizmo, you will see how quickly erosion happens and observe the long-term effects of erosion on a landscape. 1. Click Play ( ). Wait for about 20,000 simulated years, then click Pause ( ). If you want, you can drag the landscape to rotate the view. How much does the landscape change? Very little 2. Click Play, and wait for another 80,000 years or so. Based on what you see, does erosion tend to occur quickly or slowly? Slowly Explain. Erosion occurs pretty slow due to multiple factors including precipitation, temperature, and vegetation cover all not being controllable. 2018 Activity A: Effects of climate on erosion rates Get the Gizmo ready:  Click Reset ( ). Check that Landscape 1 is shown. (If not, restart the Gizmo.)  Select the Pause every 100,000 years checkbox. Introduction: Climate describes the average weather in an area over time. Climate takes into account factors such as temperature and amounts of precipitation, or how much it rains and snows. Climate also determines what types of vegetation, or plants, live in a region. In this activity, you will see how climate also affects erosion. Question: How do climate and vegetation affect rates of erosion? 1. Observe: The Gizmo shows a simplified model of erosion in a hilly area. Check that the Precipitation is 100 cm/yr (39 in/yr), the Average temperature is 20 °C (68 °F), and the Vegetation cover is 50%. Click Play, wait for 100,000 simulated years, and click Pause. The amount of eroded rock is measured in cubic kilometers (km3). A cubic kilometer is a cube that measures 1 km on each side. How many km3 of rock were eroded? 1.34 km3 2. Predict: How do you think precipitation, temperature, and vegetation will affect how quickly rocks are eroded? Fill in each blank with “increase” or “decrease.” As precipitation increases, the rate of erosion will increase. As temperature increases, the rate of erosion will decrease. As the amount of vegetation increases, the rate of erosion will increase. 3. Experiment: Click Reset. Set Precipitation to 10 cm/yr. A. Click Play and wait 100,000 years. How much rock was eroded? 0.31 km3 B. Click Reset, and repeat the experiment with the Precipitation set to 200 cm/yr. How much erosion occurred this time? 2.26 km3 C. How does precipitation affect the rate of erosion? The more precipitation per year the more erosion occurs. D. Why do you think precipitation has this effect? Because water weathers away rocks and land. (Activity A continued on next page) 2018 Activity A (continued from previous page) 4. Experiment: Click Reset and Return to original settings. Use the same procedure to see how temperature and vegetation cover affect the rate of erosion. Fill in your findings below: Erosion with temperature of 5 °C: 0.64 km3 Erosion with temperature of 35 °C: 0.63 km3 Erosion with vegetation of 0%: 1.73 km3 Erosion with vegetation of 100%: 0.70 km3 5. Draw a conclusion: What can you conclude about the effects of temperature and vegetation on erosion rates? Temperature typically has the same after on erosion no matter how high or low the temperature is however vegetation tends to erode more with less vegetation while erosion occurs less with more vegetation. 6. Infer: Weathering is the breakdown of rock into soil. A. How does weathering relate to erosion? The breaking down or dissolving of rocks and minerals on the Earth's surface is known as weathering. After a rock has been broken down, the bits of rock and minerals are carried away by erosion. Weathering and erosion are caused by water, acids, salt, plants, animals, and temperature changes. B. In general, weathering tends to occur more rapidly in warm climates than in cool climates. How does this trend explain the effect of temperature on erosion rates? Because weathering leads to the development of soil, and the rate of weathering is faster in warmer regions, erosion will occur more quickly as the temperature rises and more soil is generated, as opposed to cooler regions. 7. Explain: Why do you think increasing vegetation slows the rate of erosion? Erosion can be slowed by vegetation. Plant roots cling to soil and rock particles, keeping them from being washed away by rain or wind. 8. Compare: Click Reset and Return to original settings. Using the Gizmo, create a scenario where the maximum amount of erosion happens in 100,000 years. (Note: Do not change the rock type.) Which Gizmo settings did you choose? Precipitation: 200 Temperature: 35 Vegetation: 0 How much erosion occurred in 100,000 years? 5.72 km3 Click and drag to rotate the landscape. What changes do you notice? Small pockets of water have now appeared on the surface of the landscape. 2018 Activity B: Rock type and erosion Get the Gizmo ready:  Click Reset ( ). Check that Landscape 1 is selected and Pause every 100,000 years is on. Introduction: Sandstone is a rock made from cemented grains of sand. It is very hard and is sometimes used in buildings. Shale is a softer rock made of clay and other tiny particles. In this activity, you will compare the erosion of sandstone to that of shale. Question: How does rock type affect erosion?