EARTHSC 2B03 Lecture Notes - Lecture 3: Pedogenesis, Soil Horizon, Humus
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Formation of Parent Material
Air moves fine materials
Water can move heavier objects
Ice moves largest objects
Transportation and Deposition of Parent Material
Fast moving water can pick up heavier objects, as the water slows the heavier objects are deposited.
These materials accumulate and create floodplains along the water table level.
Glacial deposits create different soil formations and landscapes. This can be seen through the different
types of vegetation or elevations. Also by taking a look at the soil profiles.
Topography and Soil Properties
On the top of a hill, there is a very simple soil profile. The soil is dryer up on top of elevations. At the
bottom of the hill, the water that has travelled down and creates a much wetter soil, and also creates a
more complex soil profile because of all the nutrients the water brings with it. Also on the hill, there is a
lot of erosion from water, so the soil is very thin.
Soil formation is a complex process that takes place over decades or centuries. The soil pedon is an
open, dynamic system that allows additions, removals, transfers and transformations of energy and
Horizons develop as a result of numerous processes in the soil. These processes can be classified into
the following categories:
Organic and mineral master horizons are further divided into distinct horizons by adding a suffix to
master horizons. Soil pedons have distinct horizons and combinations.
Soil Master Horizons
A Horizon A mineral horizon formed at or near the surface in the zone of removal of materials in
solution and suspension, or maximum in situ accumulation of organic carbon, or both. Net-loss horizon
B Horizon A mineral horizon characterized by one or more of the following:
1. An enrichment in silicate clay, iron, aluminum, or humus
2. A prismatic or columnar structure that exhibits pronounced coatings or stsaining associated with
significant amounts of exchangeable sodium
3. An alteration by hydrolysis, reduction, or oxidation to give a change in colous or structure from
the horizons above or below, or both.
C Horizon A mineral horizon comparatively unaffected by the Pedogenic process operative in A
and B, except gleying, and the accumulation of carbonates and soluble salts.