[The Cooperative Soil Survey] Soils Tutorial: Glossary

Glossary

Definitions from the Soil Science Society of America (SSSA)

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Head slope The concave surface at the head of a drainageway where the flow of water converges downward toward the center and contour lines from concave curves.

Hemic soil material (mucky peat) Organic soil material intermediate in degree of decomposition between the less decomposed fibric material and the more decomposed sapric material.

Highwall The unexcavated face of exposed overburden and bedrock in a surface mine or the face or bank on the uphill side of a contour strip mining excavation.

Hillslope The steeper part of a hill between its summit and drainage line at the base of the hill. In descending order, a simple hillslope may include shoulder, back slope, foot slope, and toe slope.

Horizon soil A layer of soil, approximately parallel to the surface, having distinct characteristics produced by soil-forming processes. In the identification of soil horizons, an uppercase letter represents the major horizons Numbers or lowercase letters that follow represent subdivisions of the major horizons. The major horizons are as follows:O,A,E,B,C,Cr,R.

Humus The well decomposed,more or less stable part of the organic matter in mineral soils.

Hydrologic soil groups Refers to soils grouped according to their runoff-producing characteristics. The chief consideration is the inherent capacity of soil bare of vegetation to permit infiltration. The slope and the kind of plant cover are not considered but are separate factors in predicting runoff. Soils are assigned to four groups. In group A are soils having a high infiltration rate when thoroughly wet and having a low runoff potential. They are mainly deep, well drained, and sandy or gravelly. In group D, at the other extreme, are soils having a very slow infiltration rate and thus a high runoff potential. They have a claypan or clay layer at or near the surface, have a permanent high water table, or are shallow over nearly impervious bedrock or other material. A soil is assigned to two hydrologic groups if part of the acreage is artificially drained and part is undrained.

Head slope	The concave surface at the head of a drainageway where the flow of water converges downward toward the center and contour lines from concave curves.
Hemic soil material (mucky peat)	Organic soil material intermediate in degree of decomposition between the less decomposed fibric material and the more decomposed sapric material.
Highwall	The unexcavated face of exposed overburden and bedrock in a surface mine or the face or bank on the uphill side of a contour strip mining excavation.
Hillslope	The steeper part of a hill between its summit and drainage line at the base of the hill. In descending order, a simple hillslope may include shoulder, back slope, foot slope, and toe slope.
Horizon soil	A layer of soil, approximately parallel to the surface, having distinct characteristics produced by soil-forming processes. In the identification of soil horizons, an uppercase letter represents the major horizons Numbers or lowercase letters that follow represent subdivisions of the major horizons. The major horizons are as follows:O,A,E,B,C,Cr,R.
Humus	The well decomposed,more or less stable part of the organic matter in mineral soils.
Hydrologic soil groups	Refers to soils grouped according to their runoff-producing characteristics. The chief consideration is the inherent capacity of soil bare of vegetation to permit infiltration. The slope and the kind of plant cover are not considered but are separate factors in predicting runoff. Soils are assigned to four groups. In group A are soils having a high infiltration rate when thoroughly wet and having a low runoff potential. They are mainly deep, well drained, and sandy or gravelly. In group D, at the other extreme, are soils having a very slow infiltration rate and thus a high runoff potential. They have a claypan or clay layer at or near the surface, have a permanent high water table, or are shallow over nearly impervious bedrock or other material. A soil is assigned to two hydrologic groups if part of the acreage is artificially drained and part is undrained.