RM4.3 Curriculum: Rocks, Minerals, and Erosion (grade 4) Overview: Students will learn what we can do to prevent unwanted wind erosion. They will be able to write an answer to the question: How does the wind erode the soil, and what can we do to prevent this? (Students should conclude that wind is an important element of soil erosion. It causes sand/soil to be eroded from one area and deposited in another. Students should also understand that humans play a role in erosion and can help prevent it by planting trees and grass and not clearing land, which is then bare and susceptible to wind erosion.) Materials: a piece of sandpaper, a piece of wood to sandpaper, a stone to sandpaper a small jar of sand Explore: Place a pinch of sand on each student s desk. Ask students to remove the sand from their desk without touching it with anything. (Most students will have blown it off which leads to a discussion of wind being able to pick up and move objects.) Explain to the students that the Earth's landscape is continually being shaped and modified by the forces of nature. Wind, ice, water and temperature have all had a hand in making the Earth look the way it does today. These processes are called erosion, which is the wearing away of the Earth by natural processes. Today grade four is going to study how the wind changes the earth landscape. Wind erosion happens when wind blows away the top layer of soil or sand. Some of the tiny particles of sand that are carried away by the wind act like sandpaper, wearing down larger objects as they pass. Wind erosion can create and move entire sand dunes, shape rocks and other structures, and cause dust storms. The Dust Bowl of the 1930s is a good example of the damage wind erosion can cause. Show the students the 2.33min video called Wind Erosion: The Problem. It is located on youtube at: https://www.youtube.com/watch?v=etrk0tukmja ( a copy is also attached to this lesson) The students will see an example of wind erosion during the dust bowl of the 1930s. Although they talk about the United States make sure the students know the same was happening in southern Saskatchewan.) Write down the word abrasion and explain: Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. Demonstration: Take a piece of sand paper and rub it against a piece of wood. The students can see it scratching the wood away. Also rub it against some rock and again it scratches off some. Explain that as the wind picks up sand and soil and blows against rocks so over time they erode. Show some pictures of eroded rocks. (google images- eroded rocks Canada) Wind erosion is always happening but there are areas that we want to protect against it. We especially do not want the top soil of farmers land to be blown away. This top soil has most of the nutrients that help plants
grow. What happens if a farmers land loses most of its top soil? In Northern Africa many countries are suffering from the loss of fertile land. In order to grow food they must carry water many kilometers. There is a way to lessen and even prevent some wind erosion! Can anyone think of what we might be able to do to stop the wind from picking up soil and blowing it around? Hint the faster the wind blows the more able it is to pick up things. Explain that by slowing down the wind we can prevent much top soil from being moved too far. This is why it is very important to plant windbreaks (also known as shelterbelts). A windbreak or shelterbelt is a plantation usually made up of one or more rows of trees or shrubs planted in such a manner as to provide shelter from the wind and to protect soil from erosion. They are commonly planted around the edges of fields on farms. If designed properly, windbreaks around a home can reduce the cost of heating and cooling and save energy. Windbreaks are also planted to help keep snow from drifting onto roadways and even yards. Other benefits include providing habitat for wildlife and in some regions the trees are harvested for wood products. This improves the farm landscape by reducing the visual incursion of the motorway, mitigating noise from the traffic and providing a safe barrier between farm animals and the road. For maximum wind protection, the windbreak needs to be dense and tall. The ideal windbreak has a 30-50% porosity so that the air current is effectively filtered through the trees to slow wind velocity. The windbreak will influence an area about 10 times its height, for instance, a 10m windbreak will effectively reduce soil erosion over a 100m wide field. Properly installed windbreaks improve crop yields, reduce soil loss, and protect water quality. No other single farming innovation can offer so much for such a modest investment. To emphasise the importance of the windbreaks have the grade fours write down, in point form the benefits of planting windbreaks. They are as follows: Reduce wind erosion (soil loss); Filter dust and other air pollutants; Protect water quality; Provide wildlife travel corridors and habitat; Store carbon; Reduce costs of heating and cooling homes Reduce noise; Provide food and habitat for pollinator species; Protect livestock; Reduce livestock odours; Increase crop yields and increase crop quality
Show students some pictures of good windbreaks. These are printed from google images and provided at the end of the lesson. Activity: To ensure the students remember how a windbreak (shelterbelt) will help reduce the speed of wind have the class stand up and in an open area and have the students link arms. Choose a couple of students to be soil particles and place them in front of the line of students. Choose a couple other students to act as wind. The wind will go and move the soil particles easily as they are free to reach them. Now place the soil students behind the line of students that have their arms linked and represent the windbreak. The wind students must now go through the line of students to get to the soil particles. Make sure you set some guidelines like no pushing too aggressively. Students can try and crawl through the legs and so on. The point is to show that the wind must slow down a lot to get through the windbreak. You can repeat the exercise and choose different students to ensure everyone will remember how a windbreak works. Assessment: Exit slip students must write three reasons shelterbelts are important. Conclusion: During this class students learned that wind can and does erode soil and move sand. The students were shown reasons why this can be damaging for growing food. They learned that by planting windbreaks/ shelterbelt is one way to lessen the damage caused by wind erosion. They also learned that windbreaks have other advantages too. This class showed students that planting trees and shrubs are very important for the earth. *Below are pictures that can be used to show students the damage caused by wind erosion in Africa and windbreak planting examples.