Geoscience Reference
In-Depth Information
face. Moreover, pretty women should look like a cast of a famous lady, an actress,
or a feministic VIP. But there is a principal “but.” Some men look like cowards, but
everybody knows that roughly the same percentage of real cowards is found among
brave-looking men. As far as the majority of us believe, these and other facts con-
tributed to the discovery of our many recent objective tests. Hence, today, individu-
als believe and rely completely on the results of blood-related tests to detect genetic
relations, e.g., the kinship and kinfolk. And how is it with our soils? What is impor-
tant on their faces? Which features are more important than others? How does each
of them differ from the others?
We were so deeply submerged in our own argumentation that we did not notice
that our famous soil scientist left us, probably to sign another paper. We are now left
alone, but we enthusiastically continue to explain what we consider as the face of
the soil.
First, soils have their own typical and characteristic features and sizes, i.e., they
have an assortment of features at specifi c depths. In regions of mild climate, a soil
depth may extend down to 150 cm, but for a tropical climate, a depth of several
meters is nothing extraordinary. On the other hand, because of unfavorable factors
of soil evolution, shallow soils are very common within specifi c continental regions.
An excellent example is the existence of very shallow soils in semideserts caused by
a regional semiarid climate. When we try to recognize the principal features of a
soil, we often dig a pit into the soil surface having a horizontal size about 0.6 by
1.5 m that reaches a depth of 20-30 cm below the parent rock (material). Quite
frequently, we also recognize soils on the surface of continental landscapes that
were developed from river sediments (alluvium) or from dust (loess) blown into
regions by strong winds during earlier glaciations that lasted for about hundred
thousand years during the last half million years. Neither of those materials has the
appearance of a rock, but we still use the words
parent rock
for all inorganic materi-
als transformed to soil at the interface with the atmosphere.
Even a layman will recognize at least two “layers” when he carefully examines
the vertical wall of a pit dug into the soil surface. We prefer to call them
horizons
.
The name has its roots in the real, truly horizontal arrangements of these relatively
thin “layers.” They are neither inclined nor folded as it often happens to geologic
layers. Quite opposite, they are like giant thin pancakes placed fl atly one upon the
other by Goliath and monotonously extend horizontally in all directions from our
observation pit. This horizontal arrangement is the reason to call them horizons.
This terminology has prevailed more than one and a half centuries.
Each soil horizon is characterized by an accumulation of a clearly identifi able
family of materials or by the loss of some members mainly due to the dominant
direction of fl ux of water. Another distinctive sign for a soil horizon is the charac-
teristic transformation of matter by biochemical processes. When we stand in our
freshly dug pit, it is usually the fi rst time that we come face-to-face with this soil.
We try to recognize the horizons according to the color and hue. We classify the
type of the structure. Are the aggregates rounded or do they appear more like cubes
or polyhedra? Or are they platy or like fl akes? How are they separated from another?
When we wet a small clod in the palm of our hand with water and rub this wetted
