soil formations and horizons

O Horizon

Mostly organic matter

A Horizon

Topsoil, where most of the organic matter and biological activity are in the soil

E Horizon

Layer of eluviation, leached of organic matter and clay

B Horizon

Subsoil, layer of maximum illuviation, accumulation of clay or organic matter

C Horizon

Parent material, little weathering

R Horizon

Bedrock

a horizon (lowercase)

highly decomposed material

c horizon (lowercase)

cementation

f horizon (lowercase)

frozen

g horizon (lowercase)

gleying (grey color)

h horizon (lowercase)

organic matter accumulation

p horizon (lowercase)

plow

t horizon (lowercase)

clay accumulation

w horizon (lowercase)

weak

Matching Genetic & Subordinate Horizon: Bt

Accumulation of clays in the subsurface

Matching Genetic & Subordinate Horizon: Bh

Accumulation of organic matter in the subsurface

Matching Genetic & Subordinate Horizon: Ap

Disturbed surface horizon by plow

Mollic

Thick, dark colored, high base saturation (greater than 50%), good structure

Umbric

Same as Mollic, but lower base saturation (below 50%)

Melanic

Dark color, from volcanic ash, low density

Ochric

Pale, lower organic matter, thin

Histic

High organic matter, thick, wet, dark

Folistic

High organic matter (Thinner, dryer, found in cooler environments than histic)

Argillic

illuvial accumulation of high activity clay

Natric

Illuvial accumulation of sodium, greater than 15% exchangeable sodium in subsoil

Kandic

Accumulation of low activity clay

Spodic

Illuvial organic matter accumulation (Al or Fe)

Oxic

Highly weathered, kaolinite, Fe and Al oxides

Albic

light-colored, eluviation

Calcic

Illuvial accumulation of carbonates

Cambric

Some illuvial accumulation of clay