A horizon

American  

[ey huh-rahy-zuhn] / ˈeɪ həˌraɪ zən /

noun

Geology.

1. the topsoil in a soil profile.

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A horizon British  

noun

1. the top layer of a soil profile, usually dark-coloured and containing humus and from which soluble salts may have been leached See B horizon C horizon

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A horizon Scientific  

1. 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.

2. Also called zone of leaching

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Etymology

Origin of A horizon

First recorded in 1935–40

Example Sentences

A horizon of deep purple marked the afterglow of sunset and preceded a desert night of stars.

From A Man Four-Square by Raine, William MacLeod

A horizon without a few hartebeests on it would seem to be lacking in completeness.

From In Africa Hunting Adventures in the Big Game Country by McCutcheon, John T.

A horizon you could ride to in five minutes.

From The First Day of Spring by Wolf, Mari

A horizon of realisable whims opened out before Emma.

From Madame Bovary by Aveling, Eleanor Marx