Knappton soils are on mountainous uplands and have slopes of 1 to 90 percent. Knappton medial silt loam, forested. The depth to fractured basalt is 40 to more than 60 inches. The particle-size control section has field estimated 20 to 40 percent clay, and 15 to 35 percent gravel.
Reaction is very strongly acid to moderately acid.
The umbric epipedon is 10 to 15 inches thick, when present, some pedons have an ochric epipedon with moist value and chroma of 4. Acid oxalate iron is 1.5 to 3.0 percent. The A horizon has hue of 5YR, 7.5YR, or 10YR, value of 4 or 5 dry, and chroma of 2 or 3 moist or dry. This horizon has granular or subangular blocky structure. It has 10 to 15 percent organic matter.