Collect & Identify Soils
handout exercise activity exercisesuggested grade levels: 9-12
view Idaho achievement standards for this lesson

To learn more about the earth's surface, try collecting different kinds of soils in your own community. Soil is the name given to the material found above the solid rock of the earth. It consists of particles worn from rock mixed with decaying animal and vegetable matter. There are some easily recognizable common types of soil, clay, gravel, and sand, which differ in texture. Some are made up of finer particles than others and in some the particles are more closely packed than in others. For these reasons, different types of soil differ in the way they look, feel, hold water, etc. The following activity will make students more familiar with the different types of soil.

1. Students will use the Digital Atlas of Idaho.
2. Students will learn how to collect and identify soils.
3. Students will do an outdoor activity.

Use the Soil sections of the Digital Atlas. To get there: Click on Atlas Home, Geology, Basics, then on FAQ. Be sure to click on the What is Soil link and read these pages for some background information on soil. To get there: Click on Idaho Overview, then on Soils. These pages contain detailed information on different types of soil. Be sure to click on the Soil Taxonomy Key to observe characteristics of different types of soil.

Various kinds of soils Pen
Containers Trowel

These are links to access the handouts and printable materials.
geo25ho.pdf | geo25AK.pdf | FAQ | Soils

This activity can be printed out as a handout.

1. Fill clear plastic containers or glass jars with samples of sand, silt, clay, and loam (see below for definitions). It would be interesting to add to your collection samples of soil from various parts of the country, gathered during a vacation trip. Make labels for the containers, noting all the classification and location information about each sample as discussed below.

2. Soils are made up of three kinds of particle groups or 'separates', as they are called. These separates are sand, silt, and clay. But no soil found in nature consists completely of one of these separates. It is always a combination of separates. These combinations are called classes. You will want to try to identify the soil class to which each of your samples belongs. In a laboratory, a scientist would add a large amount of water to the sample, the grains would separate out and the proportions of sand, silt, and clay could be recorded. You will have to depend on cruder classification methods. The best way to do it is by texture. To determine texture, you must moisten the sample and rub it between your fingers. You can identify the sample by comparing the way it feels with the list of classes below:

Silt-A fine grained, unconsolidated sediment with particles intermediate in size of sand and clay
Sand-A mixture but largely sand; coarse and gritty to the touch; separate particles are easily seen; doesn't hold together when moist but falls apart in your hands as separate grains. Made up of large grains
Loamy sand-Holds together a little when slightly moist.
Sandy loam-Holds together when moist but hardly makes any smear on your fingers.
Loam-Makes a rough smear and feels sandy. A rich soil composed of sand, clay, and organic material.
Silt loam-Makes some smear when moist but doesn't rub out thin like clay before becoming rough and broken.
Clay loam, Silty clay loam and Silty clay-Makes smears midway between silt loam and clay when moist; are easily crushed fine between fingers when dry; particles are difficult to distinguish.
Clay-A mixture but largely clay; sticky and plastic when wet, and hard and difficult to crush when dry; when moist and rubbed between fingers, makes a smooth, thin, continuous smear; very small separate particles can be seen only under microscope.

3. You will also notice differences in the colors of your samples. They may range from black through brown, red, yellow and light gray to white. Colors do not necessarily have any connection with soil classes but you certainly should add color to the class name so that samples are described as "red sandy loam" or "white clay," etc. For more information on colors of soil, click on the Soils link above.

4. Finally, add the name of the town or city near which the soil was found. Scientists use these place names to describe soils, so you might read about "Miami sandy loam" or "Des Moines black clay loam."

Related Lesson Topics:
Geology: Geology Topics

Lesson plan by Dr. Helen Challand and Elizabeth Brandt with permission from Science Activities from A to Z.
Idaho Achievement Standards (as of 7/2001) met by completing this activity: