Soil is the surface layer of the earth, consisting of mineral and organic materials in which plants grow. Soil is arranged in layers known as horizons, with the cross section of all horizons known as the soil profile. The top horizon, or topsoil, is the dark-colored surface horizon where decomposed organic matter accumulates. There are five or more soil horizons, underlaid by bedrock.

The soil classification system is called soil taxonomy. This system has six categories or levels, ranging from orders at the highest level to series at the lowest. Twelve soil orders are recognized, with increasing numbers of classes added to each category from highest to lowest, so that approximately 18,000 series are now recognized in the U.S. Seven of the 12 soil orders and about 200 series are recognized in West Virginia.

West Virginia is divided into five major land resource areas. The Eastern Panhandle is within the Northern Appalachian Ridges and Valleys, and the southeastern part of the state is within the Southern Appalachian Ridges and Valleys. Soils in the valleys have formed in limestone or shales. They are nearly level to sloping, generally well-drained, ranging from moderately deep (less than 20 inches to bedrock) on the shales to very deep (more than 60 inches to bedrock) on the limestone. Shale soils generally have medium (loamy and silty) textures, with moderate to low pH, and moderate to low fertility. Limestone soils generally have medium to fine textures (silty and clayey), moderate to high pH, and moderate to high fertility. Some of these soils are excellent for agriculture. Soils in the mountains have formed primarily from sandstone and shale. They tend to be moderately deep to deep and have loamy to sandy textures and moderate to low pH and fertility.

The Eastern Allegheny Plateau and Mountains land resource area lies just west of the Ridges and Valleys. This area has the highest elevations within the state. Most soils here formed in acid sandstone, shale, and siltstone. They are medium textured, with low pH and fertility. The geologic materials from which the soils formed have a very low nutrient content. Therefore, some of the soils at the highest elevations are the most nutrient- poor soils, in terms of calcium, magnesium, and phosphorus, found anywhere in the state. Most of the nutrients are concentrated in the vegetation and returned to the soil when vegetation dies.

In the northwestern part of the state, the Central Allegheny Plateau lies between the mountains and the Ohio River. Soils have formed on sandstone, shale, and siltstone and are moderately deep to deep, moderately well drained to well drained, with medium to fine textures. Fertility and pH of the soils vary, depending on the parent material. Some of the best agricultural soils in the state are located along the Ohio River.

The Cumberland Plateau and Mountains land resource area lies in the southern part of the state. This rugged area has a highly dissected landscape with long, steep side slopes between narrow ridgetops and narrow stream valleys. Soils are medium to fine-textured, with moderate to low fertility, and moderate to low pH.

Glaciers were never present in West Virginia, but they did affect some soils in the state. Patterned ground and other evidence of a colder climate can be found in some soils of higher elevations. Two glacial lakes were formed, one in the Teays Valley area by blockage of the ancient Teays River in present Ohio, and one in the northern part of the state formed by the blockage of the ancient Monongahela River in Pennsylvania. Remnants of terraces formed by these lakes are still present today. Soils formed from these lake sediments are moderately well-drained and normally have fine textured subsoils from the silts and clays that settled from the lake waters.

Other evidence of glacial activity may be found in the Ohio River watershed. Three unique soils occur on terraces and on west-facing hill slopes in this area. Two soils with very coarse particle sizes formed on terraces. One formed in glacial outwash. As the glaciers to the north melted, streams of water carried sediment into the Ohio Valley. The soil formed in outwash is very gravelly and sandy. Many of the gravels are granite and other types of rocks that came from the northern U.S. and Canada and are present nowhere else in the state.

The second unique soil on the terraces is a very sandy soil formed in ancient sand dunes. During the glacial period, dry times occurred. Winds from the west picked up soil materials and blew them into present West Virginia. Sands are heavier than silts and clays and are not blown as far from the source. Therefore, they tended to deposit in mounds or dunes on the eastern side of the Ohio Valley. These sandy soils can be found from the Northern Panhandle to Point Pleasant. The silty material carried by the wind moved farther east than the sands and was deposited on the western hill slopes along the valley. The soils developed in these materials have very silty textures and high pH. They are productive soils, but highly erodible.

In a mountainous area like West Virginia, erosion may have a major effect on soil development. Natural movement of soil materials is expected on steep slopes. However, when the vegetative cover is removed, accelerated erosion may decrease the thickness of the surface horizons and carry away nutrients tied up in the organic layers. Historical records recall thick organic surface layers on soils in various parts of the state that are no longer present. Logging practices around 1900 and wild fires with the ensuing erosion reduced the surface layer thickness and sometimes the fertility of soils.

It is almost impossible to find virgin soil in West Virginia because of logging, mining, fire, flooding, and construction of roads, airports, houses, and industry. By disturbing the original landscape and soil profile, humans have restarted the soil forming process. In some places these activities have produced soils of lower quality than those before the disturbance. However, in many places these soils are changing and becoming more like the original soils because of the natural soil-forming processes.

In 1997, an official state soil was designated to symbolize the crucial importance of healthy soil resources to West Virginians. This state soil is the Monongahela silt loam, a productive agricultural soil that may be found on terraces in many parts of the state and a wide surrounding region.