Crust-related Cracks Reversible
0.1- 0.5 cm
soil structure
Irreversible
Trans-horizon Cracks Reversible
0.5 - 2 cm
Irreversible
sa
soil structure
nd
CRACKS - DEPTH - Record the Average, Apparent Depth (also called a “depth index value” in the Soil Survey Manual), measured from the surface, as determined by the wire-insertion method (≅ 2 mm diameter wire). NOTE: This method commonly gives a standard but conservative measure of the actual fracture depth. Do not record this data element for cracks that are not open to the surface. Depth (and apparent vertical length) of subsurface cracks can be inferred from the Horizon Depth column of layers exhibiting subsurface cracks. CRACKS - RELATIVE FREQUENCY - Record the Average Number of Cracks, per meter, across the surface or Lateral Frequency across a soil profile as determined with a line-intercept method. This data element cannot be assessed from cores or push tube samples.
USDA-NRCS
2-63
September 2002