Soil Survey of McHenry County, Illinois Part I - Soil Data Mart

Formation and Classification of the Soils
This section relates the soils in the survey area to
the major factors of soil formation and describes the
system of soil classification.
Factors of Soil Formation
Soil forms through processes that act on deposited
geologic material. The factors of soil formation are the
physical and mineralogical composition of the parent
material; the climate in which the soil formed; the plant
and animal life on and in the soil; relief; and the length
of time during which the processes of soil formation
have acted on the parent material (Jenny, 1941).
Climate and plant and animal life are the dominant
active factors of soil formation. They act directly on the
parent material, either in place or after it has been
moved from place to place by water, wind, or glaciers,
and slowly change it into a natural body that has
genetically related horizons. Relief modifies soil
formation and can inhibit soil formation on the steeper,
eroded slopes and in wet, depressional or nearly level
areas by controlling the moisture status of soils.
Finally, time is needed for changing the parent
material into a soil that has differentiated horizons.
The factors of soil formation are so closely
interrelated and conditioned by each other that few
generalizations can be made regarding the effects of
any one factor unless the effects of the other factors
are understood.
Parent Material
Parent material is the geologic material in which a
soil forms. Most of the soils in McHenry County were
derived from parent materials that are a direct or
indirect result of glaciers. The parent materials in this
survey area are glacial till; glacial outwash; loess, or
silty material; organic deposits; alluvium; lacustrine
deposits; and bedrock.
Glacial till is nonstratified drift transported and
deposited directly by glacial ice. The majority of till
deposits in McHenry County occur as a series of
morainal ridges and till plains that were formed as the
retreating glaciers moved eastward. There were three
different glacier formations across the county, and five
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different till members have been identified. The oldest
of these till members is the Belvidere Member of the
Glasford Formation, which is of Illinoian age (Berg and
others, 1985). It occurs in the western and
southwestern parts of the county. Danabrook soils
formed in this material. The next oldest till member,
which is late Illinoian, is the Capron Member. It is part
of the Winnebago Formation and occurs in the
northwestern part of the county. Piscasaw and Torox
soils formed in this material. The other three till
members are Wisconsinan and are part of the Wedron
Formation. The oldest of these is Tiskilwa till, which
makes up the Marengo Ridge. Kidami soils formed in
this material. The next till member, Yorkville till,
generally contains the most clay of all the till
members. The clay mineralogy is dominantly illitic.
This till member is south of Woodstock and extends in
a southerly and southeasterly direction to the county
line. Elliott and Ozaukee soils formed in Yorkville till.
The youngest till member in McHenry County is the
Haeger Member. It is sandy loam and generally
contains more gravel than the other till members. It
makes up the West Chicago Moraine, lying directly
east of the Marengo Ridge in the northern half of the
county and extending through Woodstock in a
southeasterly direction to Algonquin. Kidder and
Ringwood soils formed in the Haeger till.
Glacial outwash was deposited by running water
from melting glaciers. The size of particles varies,
depending on the speed of the stream that carried the
material. When the water slowed down, the coarser
particles were deposited. The finer particles were
carried a greater distance by slower water. Outwash
deposits in McHenry County range from loamy
sediments to sand and gravel. Landscapes include
outwash plains, stream terraces, kames, and eskers.
Fox soils, for example, formed in loamy deposits over
sand and gravel.
Sometime after the glaciers retreated, conditions
became drier and the winds increased. A thin,
discontinuous layer of silty material, or loess, was
deposited over the county directly by the winds. The
primary sources of the loess were the flood plains
along major rivers. Some of the silty material in the
county may be of local origin since it contains more