Let’s take a closer look at the top horizon.  You could also call this the surface horizon, or the A horizon.  It is dark in color.  Do you know why?  Because organic matter has been added to the soil.

Organic matter comes from the plant roots, leaves, and other material as it breaks down and decomposes in the soil.  Microorganisms use this organic matter for food.  Do you see below the second nail, the soil looks lighter?  Do you know why? There isn’t as much organic matter down there.

Now, looking at the very bottom soil horizon.  What do you notice now?  This horizon is called a B horizon, because it’s below the A horizon.  It has a much different color than the A horizon.

Does it remind you of rusty metal?  The B horizon of this soil profile contains a lot of iron, which makes the soil look so red.

How do soil scientists describe the many different soil colors?  By using a Munsell Color Book.  What you do is match a piece of your soil to a colored square in the book.

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