A horizon
–noun Geology. | the topsoil in a soil profile. |
Origin: 1935–40
A horizon
n. In ABC soil, the uppermost zone of soil, containing humus; topsoil. Also called zone of leaching. |
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Science Dictionary
A horizon
In ABC soil, the uppermost, darkest zone that is rich in organic matter. The upper section of the A horizon usually contains humus along with plant and animal matter in varying stages of decay. The middle section usually contains a high concentration of quartz or other minerals that remain following the leaching away of clay, iron, and aluminum. The lower section is typically transitional in nature between the A horizon and the B horizon. Also called zone of leaching.
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The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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