Characteristics of the Environment - Field Sampling: Principles and Practices in Environmental Analysis - page 32

FIGURE 2.4 Designations applied to the layers of loose material over rock. On
the right are typical peds found in soil.
All soil-forming—factors, time, topography, climate, biota, and parent material—are
interrelated. The amount of rainfall and the average temperature affect the types and
abundance of plants growing and animals living in a locality. The amount of water
infiltrating the soil and leaching salts out depends both on the rainfall's intensity and
amount and on topography, which influences the likelihood of rain infiltrating or running
off the surface. All of these are inextricably intertwined with the length of time these
factors are at work and the parent material they are working on.
Once a soil has developed, it is characterized and named on the basis of its inherent
characteristics. An obvious characteristic is that it has horizons. As in Figure 2.4, the
major horizons are designated by a capital letter. The A horizon is the surface horizon
usually observable because it has higher organic matter than underlying layers and is thus
darker. Under the surface A horizon will occur several other master or major horizons.
The most common are the master horizons X, E, B, and C, and they occur in this order
from the surface downward. There will also be transition horizons between all the master