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Science - 4th Grade
Standard 3 Objective 3
This activity will help students understand the components of soil.
A normal soil profile consists of three layers: topsoil, subsoil, and bedrock. Topsoil is the top layer. It is generally looser than the lower layers. It is made up of the smallest grains of rocks and minerals. The topsoil layer is usually darker in color because it contains the most dead and decayed organisms. These provide nutrients that plants need for growth. This is where plants can absorb water, nutrients and air. Subsoil is the layer below the topsoil. It is usually lighter in color because it has less living and once-living organisms. It is denser and grittier than the topsoil. It sometimes has larger rocks or pebbles mixed with small particles. Minerals in this layer are not easy for plants to use. Plants grow poorly in subsoil. Bedrock is the lowest layer or the solid rock that lies underneath the soil. It is the parent material from which much of the soil originally formed. Bedrock can be within a few inches of the surface or many feet below the surface.
4. Communicate Effectively Using Science Language and Reasoning
Invitation to Learn
Show the students a picture of a road cut or construction site. Ask them what the first thing is that construction workers do when they build houses or buildings. (Dig holes) Ask them if they have ever looked down in a deep hole. Does the soil on the sides and down at the bottom look the same as the soil on top? Why not? Discuss with them about the information in the Background (above). Explain what a profile is. Read the literacy about soil in the Student Reading.
Homework & Family Connection