Big Idea The Earth is a complex system of interacting rock,
water, air, and life!
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Weathering, Soils & Economic Geology II
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Aldo Leopold Destruction of the soil is the most fundamental
kind of economic loss which the human race can suffer. With enough
time and money, a neglected farm can be put back on its feetif the
soil is there. By expensive replanting and with a generation or two
of waiting, a ruined forest can again be made productive if the
soil is thereBut if the soil is gone, the loss is absolute and
irrevocable. Aldo Leopold
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Important distinction Weathering Erosion
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Mechanical weathering
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Frost action Web adventure: Frost at work
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An example
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Thermal expansion Solar radiation Forest fires
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Secondary crystal growth Salt growth
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Gravity
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Unloading The removal mass (A release of pressure)
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Chemical weathering Water The products of chemical weathering
are a. Dissolved minerals b. Clay c. Formation of altered or new
minerals
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Major Types of Chemical Weathering Solution Oxidation and
Hydration Hydrolysis
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Solution Weathering
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Dissolution
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Oxidation and Hydration
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Hydrolysis The most important chemical weathering reaction
(soil) 2KAlSi 3 O 8 + 2H 2 CO 3 + 9H 2 O Al 2 Si 2 O 5 (OH 4 ) + 4H
4 SiO 4 + 2K +2HCO 3 Orthoclase + carbonic acid + water Kaolinite +
silicic acid + potassium + bicarbonate
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Orthoclase to Kaolinite (Clay)
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Biologic weathering Plants Animals Humans
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Root activity
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Weathering Rates GOLDICH WEATHERING SERIES
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Olivine Quartz
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A Soil is; a natural occurring body weathered horizons of
minerals organic matter components; variable in thickness Differ
from the parent material (source)
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An important concept Soil is NOT a geologic deposit
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Soil
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Horizons Master horizons: O, A, E, B, C, and R
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O
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Soil forming factors Hans Jenny (1941) Cl, o, r, p, t cl,
climate o, biology r, topography p, parent material t, time
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Structure As a soil develops, soil peds begin to form shapes or
a structure
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Granular A-horizon
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Blocky B-horizon
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Platy
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Prismatic
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Columnar
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Texture Size of the individual peds Sand, Silt, Clay
Soil Erosion The role of vegetation!!! Stream development
Wind
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"While the farmer holds the title to the land, actually, it
belongs to all the people because civilization itself rests upon
the soil." - Pope John Paul II quoted in the Des Moines Register
July 8, 1979
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Consequences of soil erosion via stream development 1. Destroys
soil fertility 2. Degrades the health of the ecosystem 3.
Devastating for the economy a. Decrease agricultural productivity
b. Hunting c. Silts in water ways
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The Great Plains, 1920 to 1939 Poor agricultural practices and
years of drought lead to; Massive dust storms The Dust Bowl Loss of
life (human and animals) Rendered the landscape useless for at
least a decade
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Urbanization The ever growing Concrete Jungle
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Consequences of urban sprawl Agriculturally unproductive Water,
filtration, and erosion fact Residential growth drawing protests
from rural neighbors Development plans have created conflicts
across Eastern Iowa
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Annie Dillard We could, you know. We can live anyway we want.
People take vows of poverty, chastity, and obedience even silence
by choice. The thing is to stalk your calling in a certain skilled
and supple way, to locate the most tender spot and plug into that
pulse.
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Summer Workshop Check-in Sunday July 13, 11am End Tuesday July
15, 5pm