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Smith, Robert (ed.) / The Wisconsin engineer
Vol. 70, No. 4 (January 1966)

Jost, Larry
Earthquakes!: their causes and characteristics,   pp. 14-18


Page 18


       The Role
                 of
CLIMATE
                 in
SOIL GENISIS
                           by
              Edward E. Bellin, meag4
SCOIL, like faith, is the substance
of things hoped for, the evi-
   dence of things not seen. It is
the starting point for all the living
things which inhibit the earth. The
flowers that grow in the garden,
the trees that tower in the woods
and forests, and the grains and
grasses that flourish in the fields,
as well as the animals that con-
sume them-all owe their existence
to the soil. Man himself, by way of
all the food he eats, is a product
of the soil.
  Soil is what is left of the rocks
that originally covered the face of
the earth after such weathering
forces as rain, sunshine, frost, and
wind have broken them to pieces.
Soil also contains the remains of
many generations of plants and
animals that have lived on the
earth.
  Soil must be considered in rela-
tion to its environment. Soil, cli-
mate, and vegetation are all so
closely related that if one knows
the facts about any two of these,
he can deduce the facts about the
third.
            CLIMATE
  Soil-forming processes are di-
rectly affected by climate. Climate
determines the kind of vegetation
predominating in any region. It af-
fects the percolation rate in the
soil by the amount of precipitation,
the relative humidity, the tempera-
ture, and the length of the frost-
free period.
  Some of the direct effects of cli-
mate on soil formation include:
  1. A shallow accumulation of
    lime in areas of low rainfall.
  2. Acid soils in humid areas due
    to intense leaching.
  3. Thin soils on steep hillsides
    because of the quantity and
    intensity of rain producing
    erosion.
  4. Deposition of soil material
     downstream.
  5. More intense erosion in warm
    regions where the soil does
    not freeze.
  Soils come from rocks. The rocks
will weather to form the parent
material of the soil. The parent
material will weather to form the
JANUARY, 1966
soil itself. Some of the weathering
forces are: rain, sunshine, frost,
and wind. Water, wind, gravity,
and ice will transport the soil. The
parent material of the corn-belt
was deposited by the wind. The
parent material in the northern
part of the United States and the
marine sediments along the Gulf
and Atlantic coasts were deposited
by glaciers. Therefore, weathering
is another way to express the cli-
matic effects on the soil. There are
essentially two types of weather-
ing; namely, physical or mechan-
ical weathering, and chemical
weathering.
       Physical Weathering
  Temperature. The most uni-
versal type of physical weathering
is that which is produced by
changes in temperature. Expansion
and contraction in the superficial
layer of the rocks, when of suf-
ficient magnitude and suddenness,
can result in strains leading to
shattering. This type of weathfer-
ing occurs mostly in dry climates
where great changes in tempera-
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