Soil and erosion unit: Section 1

This two week unit will involve descriptive information on North Carolina soil types and how the presence of plants affects soil erosion. Upon completion of Section 1, you may continue to Section 2.

A lesson plan for grades 9–12 Science

By Amy Robertson

Learn more

• States of Soil Formation images of how soil develops from Encarta
• Cross Section of Soil a photo of exposed soil showing the different layers

Related pages

• Intrigue of the Past: Teach your students about North Carolina's fascinating past. This edition contains lesson plans about the fundamental concepts, processes, and issues of archaeology, as well as essays for the teacher with detailed information about four periods in North Carolina's ancient history.
• Great Dismal Swamp National Wildlife Refuge: Located in Camden County on scenic U. S. Highway 17, the original Ocean Highway, just three miles south of the VA/NC border, the Great Dismal Swamp Center sits on the banks of the Dismal Swamp Canal, part of the Atlantic Intracoastal Waterway.
• North Carolina Coastal Federation: Visit the North Carolina Coastal Federation and learn about the projects that the NCCF is doing toward restoration of coastal areas in North Carolina.

Related topics

• Learn more about environmental science and science.

Legal

Learning outcomes

Students will:

• Describe the relationship between climate and soil formation, and identify different soil types and how they influence soil characteristics.
• Think critically about the effect of vegetation removal on soil fertility.

Teacher planning

Time required for lesson

2 weeks

Materials/resources

• textbook
• computer
• vocabulary handouts

Materials needed for lab: six lab stations with four students at each

• safety goggles
• tongs
• sugar
• Bunsen burner
• methylene blue solution
• ring stand
• wax pencil
• calibrated scale
• garden soil
• wire gauze
• crucible
• graduated cylinder
• three test tubes with stoppers/rack

Pre-activities

Prior to the introduction of this unit, students should have studied the cycling of materials, which describes the water, carbon, and nitrogen cycles. Also, the students should have a basic knowledge of another important resource—minerals. They should come to a realization to the importance of minerals, and common methods of obtaining minerals. Concept mapping creation would be a good way to explain the relationships among minerals, elements, compounds, ores, metals, and non-metals. This would certainly be an excellent lead-in to the introduction of soils. Lastly, an extensive vocabulary sheet should be handed out to each student which will cover terminology that will be utilized in both section 1 and section 2 of this unit.

Activities

Introduction:

First obtain samples of the different types of soils from local areas around your school. Display these samples and ask for simple student identification. Mention that minerals compose a large part of the soil. Roundtable discussion: What other substances might be contained in soil?

Teacher demo:

Obtain a hammer and some shale and/or slate. Ask the students to make observations on the shale and/or slate. Lightly strike the shale/slate with the hammer. Observe. Continue striking.

Critical thinking:

What would happen if you struck some smaller particles with the hammer? Explain. Continue the striking of the hammer which should begin to cause much breakage of the shale/slate into smaller and smaller particles. Ask students to explain what will happen if you struck some of the smaller particles continually with the hammer. Explain to students that over time, the particles would continue to break apart into smaller and smaller particles. Explain that processes which break rock into smaller and smaller particles occur in nature. Tell students that as rocks break apart, they combine with other particles to form soil.

At this point it would be wise to reteach and review the role of decomposers in the environment. You should then challenge students to explain the role that these organisms play in the formation of soil. Pioneer organisms, such as lichens, and their role in the formation of soil should also be discussed. Reinforcement should be introduced by reviewing some of the vocabulary terms used up to this point.

Activity:

Provide a hand lens to each student. Distribute small samples of different types of soil (unlabeled clay, silt, and sand) to each student. Have the students attempt to identify the three types that they have been given.

Discussion:

You should then begin to introduce soil. Begin by explaining what soil is, that it is the home for many organisms, and the superficial covering of most of the earth’s land area.

Explain:

1. That it is an aggregation of unconsolidated mineral and organic particles produced by the combined action of wind, water, and organic decay, and that soils will vary widely from place to place.
2. The chemical composition and physical structure of the soil at any given location are determined by the kind of geologic material from which it originates, by the vegetation cover, by the length of the time that the soil has been weathered by the topography and by artificial changes caused by human activities.
3. The primary make-up of soil would be undissolved inorganic or nonliving components which are produced by the weathering and breakdown of surface rocks, soluble nutrients used by plants, various forms of organic matter, both living and dead and gases and water that are required by plants and subterranean organisms.

Make sure students are aware of the concepts of bedrock and parent rock.

Introduction of the three major types of soil:

You should then have the students observe their soil samples more intensely than before. Begin the explanation of the types of soil:

1. Sand—particles ranging in size from 2–0.05 millimeters in diameter, good drainage and good aeration, but does not store water very well. Therefore, this last characteristic makes sandy soil quite unsuitable for plant growth.
2. Clay—particles are usually smaller than 0.002 millimeters. Clay particles are invisible to the naked eye and form a gummy mass when wet. They hold water very well, but they do not drain well and do not contain much space for air and not likely to sustain many plants.
3. Silt—particles range from 0.05–0.002 millimeters. They can scarcely be seen without the aid of the microscope and feel like flour when rubbed through the fingers. By this time the students should have identified the three types and they should be allowed to feel by touch and make assumptions by discussion on the types.
4. Lastly, make inference about the fact that loam soils are a combination of roughly equal amounts of sand, clay, and silt particles and that according to the proportions of the three soil types, that they are further broadly classified into several arbitrarily defined textural groups.

Activity:

Each student should be given a clear plastic cup and additional samples of the three soil types and some rock particles. This would be a good time to show the image: “cross section of soil”

Introduction:

Presentation on a soil profile. Students should then individually create a model soil profile for a mature soil. Indicate to them to include all layers or horizons (A-topsoil, B-subsoil, C-partially weathered bedrock, and R-bedrock), and that they need to label the horizons. This would be a good time to show the image “Stages of Soil Formation”

Lead in to Section 2:

Help students recognize how planting the same types of plants in an area year after year could deplete the soil of certain nutrients.

Final activity for section 1:

Laboratory activity: “Looking for life in soil”

Time required: Day 1—forty-five minutes, Day 2—fifteen minutes

Inference: living organisms give off carbon dioxide gas.

Pre-lab:

Read entire lab layout. State a hypothesis as to what gases you (students) think will be given off by living organisms in a stopped up test tube.

Make sure your students have been prepped prior to this lab as to correct safety procedures.

1. Make a data table listing each test tube (label A, B, C), their contents, and observations on day 1 and day 2.
2. Label each test tube: A, B, C
3. Transfer one gram of the soil to the crucible, place wire gauze and crucible on the ring stand over Bunsen burner. Wear safety goggles.
4. Heat the soil in the crucible for ten minutes.
5. Use tongs to remove the crucible.
6. Transfer one gram of unheated soil to test tube A. Add one gram of sugar and ten milliliters of methylene blue solution, which is an indicator of carbon dioxide.
7. To test tube B, transfer the heated soil from the crucible, one gram of sugar, and ten milliliters of methylene blue solution.
8. To test tube C, transfer one gram of sugar and ten milliliters of methylene blue solution.
9. Observe the liquid in each test tube. In the day 1 column of your observation data table, describe the colors using the terms blue, light blue, and colorless.
10. Put a stopper in each test tube and shake well. Put back into test tube rack and leave over night.
11. Day 2: observe the test tubes again. Do not shake. Record observations in the Day 2 column using same terms as you used before (colors or colorless).

Analysis: Question and answer?

• What was the purpose of heating the soil that was placed into test tube B?
• Carbon dioxide causes methylene blue solution to change to light blue or colorless. What color changes did you observe in each test tube on Day 1? Day 2? What do these color changes indicate?
• Was your inference accurate? Support your answer with data.

Conclusion:

Does soil contain any living organisms? What evidence do you have to support your answer? Explain your conclusion.

Assessment

• Review all discussion presented. A good way I review when I present a lot of material on a subject is that I play a review game of some sort which is usually jeopardy or basketball. I also use the game of “Bluff,” which has been very successful as a review of concepts studied.
• Evaluate all laboratory materials/questions given by each lab station. I also grade on each station’s productivity in the lab, such as active participation, follow-through, behavior. I make sure that all material in done in scientific method format.
• Continue seeing progress on vocabulary work which will be finalized at the end of section 2.
• Quiz students on knowledge acquired through variable testing
• I place a big component of assessment in the interest I can visually observe in my students, in particular with their active participation in class discussions.

Supplemental information

Attachment:

• Bluff descriptions and instructions

Critical vocabulary

• water cycle
• carbon cycle
• nitrogen cycle
• mineral
• shale
• slate
• decomposers
• pioneer organism
• topography
• inorganic material
• organic material
• weathering
• solubility
• subterranean organism
• bedrock
• parent rock
• silt
• sand
• clay
• soil profile
• loam
• topsoil
• subsoil

Comments

I received pertinent information from the North Carolina Forestry Services that was of tremendous use in the introduction of this unit.

Laboratory demos/activities were incorporated from a variety of sources such as textbooks, resource books from several sources and personal college materials.