The soil forming processes result in the development of distinct layers, or soil horizons. These horizons can be viewed in a vertical cut of the soil, called a soil profile. The profile extends from the surface down into material that is little affected by soil forming processes. These processes include accumulation of organic matter, leaching of water soluble salts and mineral elements, relocation of clays, reduction and relocation of iron, and formation of dense subsoil layers called fragipans (Simonson, 1959).

Most profiles contain three major types of horizons: A (topsoil), B (subsoil), and C (substratum) horizons (see figures in the Map Unit Description section). The Glossary, the Soil Survey Manual (Soil Survey Staff, 1993), Soil Taxonomy (Soil Survey Staff, 1996), and The Nature and Properties of Soils (Brady and Weil, 1996) give more information about different types of horizons and their formation.

The accumulation of organic matter takes place as plant residue decomposes. This process darkens the surface layer and helps to form an A horizon. Wetter soils such as Rippowam and Wallkill have thicker and darker A horizons than drier soils (Fig. 12). Organic acids dissolved in percolating water increases leaching and mineral breakdown (weathering). Weathering is a continual process that changes rocks and minerals into elements that go into solution in the soil water. Leaching of dissolved elements, lime, and other salts takes place as the soil water moves down and out of the soil. Sandier soils such as Penwood and Manchester, and soils with permeable subsoils, such as Cheshire and Maplecrest have the highest leaching rates.

The reduction and relocation of iron compounds occur mainly in wetter, more poorly drained soils. Grayish color in the subsoil indicates that the reduction of iron has taken place; yellowish brown and reddish brown mottles indicates the relocation and accumulation of iron (Fig. 12).

Clay particles are transported downward in suspension with soil water from the A horizon and redeposited in the B horizons as films and linings in pores and root channels. An E horizon forms in some soils after considerable clay and iron has been leached from the layer above the B horizon. The processes that lead to development of a dense subsoil layer (fragipan) are not yet understood, but may involve the movement of clay and aluminum into the dense layer. Ludlow and Wilbraham soils have a dense subsoil above a dense glacial till substratum.

Soils are natural, three-dimensional bodies at the earth's surface that formed through the interaction of parent material, relief, climate, and plant and animal life over a period of time (Jenny, 1941). The influence of each factor differs from soil to soil, and each factor modifies the effect of the others.

Parent material is the unconsolidated earthy material and rocks in which soils form; it determines the mineral and chemical makeup of the soils and exerts a strong influence on the rate that the soil forming processes take place. The nature of the parent material is the most important factor influencing the properties of the soils in the survey area. The Geology section contains more details about the relation between soil and parent material type.

The relief factor is partly the slope, the shape of the land surface, and the position of the land in relation to the to the water table. Soils that formed in convex, sloping areas where runoff is medium or rapid, generally are well drained and have brighter red subsoils than soils in lower parts of the landscape. In more gently sloping areas, the soils are usually wetter for brief periods and have mottles in the subsoil. In lower areas where the water table is at or near the surface for long periods, the soils are not leached or highly developed and have thick, dark-colored surfaces with grayish subsoils (Fig. 12). Table 1 gives the relation between parent material, relief (landscape position), and drainage class of the soils.

Climate determines the nature and rate of weathering processes that occur, influences the kind and amount of vegetation that grows on the soil, and determines how much water is available for leaching processes. All soils in the survey area have been under similar climatic influences.

All living organisms, including plants, animals, bacteria, fungi, and humans, affect soil formation. Earthworms and burrowing animals keep the soil open and loose. Vegetation affects the kind and amount of organic matter that enters the soil, and bacteria and fungi growth determine how much and how fast the organic matter is decomposed. Grass vegetation in the marshes that was not decomposed completely led to the buildup of dark organic surface horizons. Humans have changed soil properties by adding lime and fertilizers, moving soil around with large machines, depositing large amounts of garbage and rubble, and causing severe erosion.

Many decades of time are generally needed for significant changes to take place in the parent material; the darkening of topsoil by organic matter and development of soil structure near the surface are exceptions and may take place in shorter periods of time. Most soils in the survey area have been forming since the end of the glacial period, and have developed distinct soil horizons. The human-transported soils have been forming for a very short period of time, and show little subsoil development. The floodplain and marsh soils are being continuously deposited and have thick darkened surface horizons but have not been in place long enough for the soil forming processes to make distinct differences in the subsoil layers.