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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

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27% Clay

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Figure 4.16

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Moldboard Plow

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Figure 4.19

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Figure 4.22

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Soil classification (Naming) Pedologists Why Classify anything?

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Soil Taxonomy Order 12 Suborder 63 Great Group 319 Sub Group 2, 484 Family 8, 000 Series 19, 000

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The official Iowa state soil The Tama series Fine-silty, mixed, superactive, mesic Typic Argiudolls hyperlinked

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Order: Mollisol Temperate Grasslands Thick A-horizon

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Soil Problems & Consequences

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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