The Dirtmeister is your personal guide to hands-on science exploration in the classroom. By participating in Dirtmeister's Science Labs, kids have the opportunity to experience science firsthand. The steps in completing the challenge follow the same methodology used by scientists in solving problems. After reading the question, students are encouraged to formulate hypotheses. With science expert Steve Tomecek (the "Dirtmeister") serving as facilitator, students complete the hands-on investigation and check their results against their predictions.
Teachers who participate in the challenge also have the opportunity to gain valuable experience in teaching inquiry-based science because each new challenge helps to reinforce basic science concepts. For personal advice and support from Steve, join the Hands-On Science discussion in the Teacher Center.
In this experiment we explore the changing surface of the Earth and discover the effects of erosion. By setting up a simple model of a stream, students see how slope, soil texture, and cover affect the amount of erosion that occurs on soil. In addition, by comparing the clean "rain" with the water that runs off the soil, students begin to get an understanding of why erosion causes additional problems of downstream sedimentation in ponds and lakes.
Erosion is a natural process. Any time water flows over the land surface, it works to remove soil particles from the upstream end and deposits them in low-lying areas, generally causing the surface to level out. In fact, if it weren't for tectonic processes deep in the Earth that cause periodic uplift of the land, the surface of our Earth would be flat as a pancake! Three key factors help to control how much erosion will occur. First and foremost is the slope of the land:
- Slope: The steeper the slope, the more kinetic energy a stream will have and the better equipped it will be to remove loose particles. All the energy to do the work is supplied by gravity. In many cases, fast flowing streams not only pick up soil grains, but they can transport larger rocks by rolling them along the bottom.
- Soil Texture: The second controlling factor is the actual grain size of the soil particles themselves. Most soils contain a large variety of particle sizes ranging from coarse sand (about 2 mm in diameter) to microscopic clay particles. Generally speaking, the finer the particle size, the more easily the soil will be eroded. If you've ever waded in a mountain stream, you may have noticed that the center channel is often lined with coarse gravel. This is because in the "high energy zone" most of the finer material has already been swept away. You can also see the effects of soil texture in the muddy appearance of rivers after a storm. They often look like chocolate milk for several days because the fine-grained clay particles easily go into suspension. These particles stay afloat until the stream enters a lake or pond where the energy level is minimal.
- Cover: The final factor that helps to control the amount of soil erosion is cover. Any farmer can tell you that the worst erosion occurs on a field that has just been plowed. Without the roots of trees and grass to hold the particles together, soil will become rapidly eroded, leaving a bulk of the soil somewhere downstream. Plants also help to reduce the energy of running water by literally serving as obstructions to the flow. Finally, leaves of plants help to dissipate the energy from rain drops hitting the ground. As a result, streams don't get the "head start" they need to really get erosion going.
Learning Outcomes/National Standards Correlations
The Dirtmeister's Science Lab on levers helps students meet the following science content standards as set forth by the National Research Council of the National Academy of Sciences:
- Soils have different physical properties. (Content Standard D).
- Soils have properties of color and texture and have different capacities to retain water. (Content Standard D)
- The surface of the Earth changes. Some changes are due to slow processes such as erosion and weathering. (Content Standard D)
- Landforms are the result of a combination of constructive and destructive forces. Destructive forms include erosion and weathering. (Content Standard D)
- Soil consists of weathered rocks and decomposed organic material. (Content Standard D)
Managing Time and Students
Classroom management is always a critical factor for any successful lesson, and the Dirtmeister's Science Lab is no exception. The following strategies will help to maximize the use of the activity in various classroom situations:
The activity can be used as a class demonstration integrated into a larger unit on erosion. In this case, all students can make predictions while one or two volunteers can carry out the activity in front of the room. For a more hands-on discovery approach, it is recommended that students work in groups of 3-4, sharing their predictions and observations. With the entire class working in teams, the hands-on portion of the challenge will take approximately 30 minutes to complete. While younger students (grades 1 and 2) should have no problem making observations, they may have problems controlling the flow of water from the watering can. It may be possible to get some older "student buddies" from another class to assist with the experiment or you as the teacher can go from station to station.
Here are some suggestions to enhance the experience of Dirtmeister's Science Lab for your students:
Extensions on Erosion
- Have the class observe an actual field area before and after a rainstorm to see if any erosion has taken place. They should look for places where the water has cut little channels in the soil, or where small piles of sand has been deposited.
- After a storm, water in a pond can stay turbid for several days due to suspended clay particles. Scientists measure turbidity using a device called a "Secci Disc," but students can make their own "mud meter" by taking a white piece of plastic and painting black stripes on it. Tie a fishing weight to the bottom of the disk and slowly lower it into the water until it disappears. Measure the length of the string below the water surface and record the depth. Come back a few days later and repeat the experiment. If the water has cleared up, they should see the disk in the water to a deeper depth.
- Soil texture (the relative combination of sand, silt, and clay present in the soil) differs from one area to another. To see how different soils "stack up," take a one-quart glass jar with a lid (a mayonnaise or pickle jar works great) and fill it about 3/4 full of water. Add 1 cup of soil and shake for 10 seconds. Allow the soil to settle for a few minutes and you will see different layers appear. The coarse material (about the size of sand) will settle to the bottom first, followed by the silt and then the clay. By looking at the relative thickness of each layer, they can get a sense of what their soil is made of. Try a bunch of different soils to see how each "stack up."
- Where does the sand on a beach come from? Why are rocks in a stream usually round? Most people don't realize it, but soil starts out as rocks. These rocks have been broken down by a process called weathering. If you want to see weathering in action, take 3 or 4 small rock specimens and put them in a large plastic container filled half way with water. Place a lid tightly on the container and have the students take turns shaking it as hard as they can. Do this for a total of 10 minutes. Open the lid and look inside. Where did the dirty water come from? Did any of the rocks change shape? They'll quickly discover how rocks can roll and in the process make sand!
- Have the class use the computer to search the web for supplementary articles on soil erosion and its protection. A good place to check is the USDA Soil Conservation Service.
- Provide space on a classroom bulletin board for the Dirtmeister's Science Lab. Assign different teams of students the task of designing the board and changing the postings to reflect the different Science Lab topics throughout the year.
- Using computer software such as ClarisWorks(TM) or Microsoft Works(TM), have students create and maintain electronic science journals. Encourage students to illustrate their work by using drawing or painting features of the software. This is an excellent way of keeping notes and storing the labs for future use.
- Have each student write an article about their favorite science experiment. Compile the articles into a science newsletter. If your class already publishes a monthly newsletter, feature a science topic in each issue, rotating the responsibility of writing the articles throughout the class.
The following Scholastic supplemental materials can be used in conjunction with Dirtmeister's Science Lab.
Big Books: Science (Grades K-4). This book series covers a variety of topics, from bugs to wind. They are brightly illustrated and great for the classroom library.
Environmental Atlas of the United States, by Mark Mattson (Grade Levels 4 and up). The only environmental atlas for young readers that emphasizes U.S. ecological information.
Be a Scientist skills books (Grades 3-6). This series includes featured scientists, hands-on activities, and an emphasis on practical process skills. The series consists of three sets of three books each for grades 3-4, 4-5, and 5-6.
Super Science (Grades 3-6). High-interest articles and hands-on activities teach basic science and technology concepts. Each theme-based issue presents timely news and stimulates students' interest through fun activities. Exercises develop critical-thinking skills and help you meet the Natural Science Education Standards.
Quick and Easy Learning Centers:Science, by Lynne Kepler (Grades 1-3). This Professional Resource book focuses on the use of everyday materials to promote independent, hands-on learning. Information on how-tos, management, experiments, and reproducibles are included in this helpful book.
Call Scholastic directly at 1-800-724-6527 to order and for more information.