Name ends in id . Spodosol - spod from the Latin spodos, or wood ash. These soils have a spodic, or ash-colored horizon. They usually form under conifer forests, which help leach OM, and Fe and Al oxides to form the spodic horizon. Spodosols are common in NE US, Canada, N. Europe, Siberia.
Name ends in od .
PT classification determined visually. Atterberg further defined limits, based on moisture content, to differentiate between the 4 states. Atterberg limits are determined procedurally using standardized tests.