Geoscience Reference
In-Depth Information
Living plant
shoots/grass
Additions of dead plant
matter from previous year
Transformation of organic
matter into humus by decay
Translocation of dissolved
minerals by eluviation
Accumulation of eluviated
minerals by illuviation
(a)
Figure 11.7 How additions and translocations affect soil development.
(a) One way
that additions occur in soil is through the accumulation of dead plant matter, which slowly
transforms into humus by decay. The processes of eluviation and illuviation move materi-
als vertically through soil. Eluviation moves material, such as dissolved minerals, out of
the upper soil. These minerals recrystallize and accumulate in the lower part of the soil by
illuviation. (b) In this photo of actual soil, the dense-looking whitish layer toward the base of
the soil is calcium carbonate that was eluviated by water moving downward from the upper
part of the soil.
(b)
recrystallize and collect. When water moves materials,
usually in the form of minerals, clays, and organic matter,
out
of the uppermost part of the soil, the process is called
eluviation
, or leaching. When leached materials from the
upper part of the soil recrystallize
within
the lower part
of the soil, the process is called
illuviation
. Figure 11.7
shows the results of the combined processes of eluviation
and illuviation.
4.
Transformations
Transformations refer to the decom-
position of minerals and organic matter into other forms
within the soil. An excellent example of a transformation
is when organic matter, such as leaf and animal litter, de-
composes into humus. Another example is when minerals
are transformed into other minerals or are made smaller
by weathering. In addition, soil particles begin to clump
together in a recognizable structure.
VISUAL CONCEPT CHECK
11.1
Which one of the following choices describes how these
fall leaves are related to soil development?
a)
Soil losses
b)
Soil additions
c)
Soil transformations
d)
Soil depletions
Eluviation
The dissolution and downward mobilization of
minerals by water in the soil.
Illuviation
The recrystallization of minerals that occurs
directly below the zone of eluviation.
