Hidden Horizons
Below the line at which the land appears to meet the sky, there are other horizons. These “hidden” horizons are the descending layers within a soil. Horizons are the visible evidence of soil-forming factors at work—climate, organisms, relief (topography), parent materials, and time.
In some soils, the boundaries between layers may be sharp; in others, the composition of the layers gradually changes. Not all soils have horizons, but by “reading” soil layers, along with observing moisture content and temperatures, scientists can classify or describe soils.