Deep Layers: The Soil Horizons Quiz

If a layer sits at the very top of the profile, then it receives falling plant litter; if it consists of mostly undecayed organic material, then it is designated as the O Horizon.

If plants and insects live near the surface, then they interact mostly with the upper mineral layer; if this layer is rich in organic matter (humus), then it is the A Horizon or topsoil.

If water moves downward through the soil, then it carries small particles and minerals with it; if these materials are washed out of a layer, then the process is called eluviation.

If minerals are leached from the A and E horizons, then they must settle in the layer below; if the B Horizon receives these materials, then it is the zone of accumulation.

If the C Horizon is deep in the profile, then it is far from surface biology; if it sits directly on parent rock, then it consists of broken rock pieces, making all listed traits true.

If the bottom-most layer of a soil profile is a solid, unweathered mass, then it is the parent material; if it is solid stone, then "R" stands for Rock or Bedrock.

If the E Horizon is the "Exiting" layer, then minerals and organic matter have been leached out; if these coloring agents are gone, then the layer is light-colored, not dark.

If you look at a cross-section of the earth to see the layering, then you are viewing a summary of its development; if this summary is a vertical slice, then it is a soil profile.

If organic matter decays at the surface, then it turns into dark humus; if the A Horizon contains this concentrated humus, then it will appear darker than the mineral-heavy B Horizon.

If climate affects weathering and slope affects erosion, then they change layer depth; if time allows layers to grow, then all these factors collectively control horizon thickness.

If leaching requires water to carry minerals downward, then it needs significant rainfall; if deserts lack rainfall, then leaching is minimal, making the statement false.

If weathering starts at the surface and moves down, then the deepest layer is the least changed; if the R Horizon is the deepest, then it remains solid, unweathered rock.

If eluviation is the "exit" of minerals from an upper layer, then there must be an "into" process for the lower layer; if they are deposited in the B layer, then it is illuviation.

If erosion removes the topmost layers of soil, then the organic-rich surface is washed away first; if the A Horizon is the surface mineral layer, then it is the most likely to be missing.

If clay particles are very small, then they are easily moved by water; if water carries them down from the A and E horizons, then they accumulate in the B Horizon.

If plants and animals die and decompose, then they leave behind a stable, dark substance; if this substance provides nutrients to the soil, then it is called humus.

If dark colors mean humus and red colors mean iron, then color indicates composition; if gray colors mean poor drainage, then color provides all the listed information.

If needles from evergreens make the soil acidic, then minerals dissolve and wash away faster; if this intense leaching occurs, then a distinct, light-colored E Horizon forms.

If the "Solum" refers to the "true soil" where biological and soil-forming processes are most active, then it includes the top and subsoil layers but excludes the parent rock.

If soil formation depends on climate and time, then different environments produce different layers; if a soil is young or in a desert, then it may lack an O or E horizon.