Soil Profiles


Think about this. . . Let's say that you have a dog named Digger, Look to the left. Digger was given his name for a reason. Digger really likes to dig. All day long when you are at school he digs. It is probably a good thing this dog is imaginary. Because the virtual dog that we have provided for you would make one big mess in the your real-world backyard. As Digger goes about doing his daily thing, what will he find? (Besides the bones he buried the last time you had pork chops for dinner)?


Of course the answer to that question depends on your backyard. But unless your backyard is covered in maintainence-free concrete, Digger will probably find different types of soil. If he digs deep enough Digger might eventually hit solid rock. Do you know what it is called? (Hint: Think Flintstone town) The answer, of course, is bedrock. But before Digger reaches the bedrock, he will have dug through three or four different layers of soil. These layers makeup the what is called a soil profile. Each of the layers of soil is called horizons.


Click on the picture above to go to

Bedrock Cities


Here is your chance to be a virtual millionaire again. The first layer of soil (the first horizon) usually darker. What do you think causes this layer to be darker?

A. The sun tanning the surface of the soil?
B. The inorganic materials in the soil?
C. Leftover volcanic debris?
D. The organic material in the soil?

Is that your final answer? Okay, smartie you were correct. It is the organic material in the soil. Hey, it's too bad that this is only the virtual version of "Who Wants to be a Millionaire."

The first horizon-or layer-is usually darker in color, often blackish because it is mostly made of organic matter. This horizon is also called the topsoil. In general, Utah and other dry, western states have less organic matter than other places in the United States that have more yearly precipitation and plant life. In these areas with more moisture and vegetation, you will find that the layer of topsoil goes much deeper than in Utah.
When Digger burrows his way past the topsoil, he will reach the subsoil. This soil horizon is usually lighter in color than the topsoil. The subsoil is often brownish and less productive than the topsoil. Minerals in the subsoil not in a form that are easy for plants to use. The subsoil is mostly made up of clay or sand and has very little organic matter in it. Between the subsoil and the bedrock is a layer of small rocks that have started to break off from the bedrock. This layer is called the parent material of the soil. This is the material that will eventually become the soil. The minerals in the parent material will determine the composition and the other characteristics of the soil. The bedrock layer is solid, uniform rock at the bottom of the profile.


By clicking on the gelatin square below, you can find out more about soil profiles. Use this site to make a "Soil Profile" poster or model. Be sure to label each horizon.

Use information from the site mentioned to make an edible model of a soil profile. Hint: Do not use the real stuff (dirt) for this project. The whole point is to enjoy devouring the project when you finish. So use your imagination here. Think in terms of your favorite food. Hey, you can even take gelatin and make a pretty good soil profile. Think about it!


Ask your teacher or parents to help you find an area where you can analyze soil to determine a soil profile. Of course you may not be able to dig down to the bedrock, but you might be able to determine the depth of the topsoil and/or other soil horizons. Be sure to be a thorough scientist and take pictures of the area. Measure each soil horizon and collect samples. Your class may want to work in different groups and share information with each other.

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Updated August 7, 2001 by: Glen Westbroek

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