The arrangement of soil particles into larger particles, or clumps. Platey structures are formed of thin, horizontal layers; prism-like structures are called columnar where the tops are rounded, and prismatic where the tops are level; blocky peds are bounded by flat or slightly rounded surfaces; and spheroidal structures are called crumbs if highly water absorbent, and granular if only moderately so. See Levine et al. (1996) Ecol. Model. 92, 1.