The Layers of Soil
Lesson 3 of 8
Objective: SWBAT describe the layers of soil and how they form.
In this lesson, students learn that there are layers of soil below the surface and they make a detailed model of the layers. This aligns to Essential Standard 1.E.2.1, "Summarize the physical properties of Earth materials, including rocks, minerals, soils, and water that make them useful in different ways". Understanding the layers of soils will help students to later understand that different types of plants have to be planted at different depths to survive, and that certain other materials, like water and minerals, are drilled out from other depths. This lesson also adds to their overall knowledge of the properties of soil. My essential question for today is: "What are the 5 layers of soil? What does each layer look like?" Listen to my Explanation of Essential Standards and Essential Question.
*Dark brown, light brown, grey, and green construction paper
*Crayons of different colors
*Scissors and glue
This lesson includes lots of vocabulary, so I start with a poster with the pre-started or printed diagram of the layers of soil on a chart clearly labeled and I introduce them to the class. I say,
"Today, we are going to learn about the layers of soil. The top layer is called topsoil - because it is at the....top! Then, there is subsoil. The prefix 'sub' means 'beneath', like a submarine that is beneath the ocean, so subsoil in beneath or below the topsoil. Then, under all of that -- way far below --is bedrock. We are going to sing a quick song to practice those words!"
We sing this song together and I teach the students hand motions for topsoil, subsoil, and bedrock as we go along so they get a visual representation of the layers to match the poster diagram and the vocabulary words. Although the song does not have pictures to go with it on the screen, I use the pre-made poster to illustrate what the song is saying.
Then, I say,
"Now we are going to watch a quick video which will tell us two additional layers and give us a bit more detail - listen carefully and see if you can figure out what the other two layers are".
Although the video is a cartoon and I would have preferred it to be real images, the video has great, clear information and uses vocabulary and language that is perfect for first graders, so I still like it! After the video, I make sure the students can tell me the additional two layers and I add them in to my poster.
Then I show this computer model of how bedrock breaks up because of temperature, organic matter, the original minerals, and water causing weathering.
I like to use media to engage students in the beginning of science lessons because it gets them excited and it really gets their attention. It also supports Science and Engineering Practice 8, obtaining scientific information through media to determine information about the natural world.
For the activity, I say to my students,
"Today, we are going to make a paper model of the 5 main layers of the layers of soil. We learned what they were - turn to your neighbor and see if you can tell them all 5!"
After I give students a minute to try to recall all 5, I say,
"Okay, so why do scientists use models? That's right! To help them remember things like the 5 layers of soil - and which order they go in! So, this is how we are going to make this model".
Then, I show them the dark brown construction paper that will be their background and will not get cut at all. We start at the bottom, by cutting some bedrock out of grey construction paper and gluing it to the bottom of our dark brown paper. Then we add weathered rock fragments. As we go through each part, I talk a little bit more and refer back to this diagram of the Soil profile on the Smart Board to show how the bedrock breaks apart more and more as we get towards the subsoil and the topsoil. We add subsoil by changing the color of the background by coloring with a crayon and adding some sparkling minerals (glittery crayons!). This also allows us a very brief review of minerals because we just finished learning about those, too! Then we finish our model with topsoil, using white crayons to make roots and green paper to make grass and flowers on top. We may even add a worm and an insect or two!
Making scientific models supports Science and Engineering Practice 2 to represent a system - in this case, the layers of soil.
After we have finished our models, I say,
"Now that we have made great models, do you think that any other scientist would know exactly what it was? Well, maybe! What is one last thing we can do to make sure that what we learned can be shared information? That's right - we can label the layers. We are going to use the sticky labels again. I will give you five labels. Copy the words clearly and correctly, and use the poster or the diagram on the board to make sure you get them in the right place! Scientists have to make sure their work is accurate!"
Throughout this model making activity, I check to make sure that the student's work is accurate and that they understand that this is a sequential process and not really a creative artistic one!
To wrap up this lesson, I review the poster with my students and go over the vocabulary again, reiterating that the reason for the layering in the soil is because of the different organic materials in the humus breaking down at the top causing rich soil and the bedrock at the bottom cracking apart like the computer model showed moving due to shifting soil and movement towards the surface. Then, I revisit the questions that my students during the first soil lesson we did and see if we have found out any of the answers, and see which ones we are still looking out for! Asking questions to find out about the natural world supports Science and Engineering Practice 1 and communicating information and ideas using models, like we did throughout this lesson, supports Practice 8.