Soils A Behavior of Rocks and Soils 1

Soils A. Behavior of Rocks and Soils 1. Review of terms

Soils A. Behavior of Rocks and Soils 1. Review of terms a. Stress (pressure) s = F/a Units?

Soils A. Behavior of Rocks and Soils 1. Review of terms a. Stress (pressure) s = F/a Units? Pascals N/m 2 or kg/ms 2

Soils A. Behavior of Rocks and Soils 1. Review of terms a. Stress (pressure) s = F/a Units? Pascals N/m 2 or kg/ms 2 Types of Stress 1. 2. 3. Compression Tension Shear

Soils A. Behavior of Rocks and Soils 1. Review of terms a. Stress (pressure) s = F/a Units? Pascals N/m 2 or kg/ms 2 Types of Stress 1. 2. 3. Compression Tension Shear Rocks bend before they break!

Soils A. Behavior of Rocks and Soils 1. Review of terms a. Stress (pressure) s = F/a Units? Pascals N/m 2 or kg/ms 2 Types of Stress 1. 2. 3. Compression Tension Shear Rocks bend before they break! Most geologic materials are VERY strong under compression and VERY weak under tension

Think about how the stress field changes by putting a home on this slope Soil Rock Is there stress on the soil?

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope How does the building of the house affect s?

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope How does the building of the house affect s? 1. Greatly increase local slope

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope How does the building of the house affect s? 1. Greatly increase local slope 2. Notch removes support, tension in soil above as it spreads

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope How does the building of the house affect s? 1. Greatly increase local slope 2. Notch removes support, tension in soil above as it spreads 3. Water can get into tensional cracks, reduce strength and add weight, which makes more cracks

Think about how the stress field changes by putting a home on this slope Soil Rock s Is there stress on the soil? Yes, gravity pulling it down slope How does the building of the house affect s? 1. Greatly increase local slope 2. Notch removes support, tension in soil above as it spreads 3. Water can get into tensional cracks, reduce strength and add weight, which makes more cracks 4. Water and house add more mass and therefore more stress. Water can also reduce Yield strength of soil. What if stress from house and water exceeds YS of soil?

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1)

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression Units? Widen 0. 1 cm when compressed by 1 cm

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression Units? Widen 0. 1 cm when compressed by 1 cm Dimensionless

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression Units? Widen 0. 1 cm when compressed by 1 cm Dimensionless Most geologic materials have 0. 1 -0. 4

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression Units? Widen 0. 1 cm when compressed by 1 cm Dimensionless Most geologic materials have 0. 1 -0. 4 Rare = -0. 1

Soils A. Behavior of Rocks and Soils 1. Review of terms b. Strain e = d. L/L dimensionless c. Strain rate e. = e/time (s-1) d. Poisson’s ratio – ratio of thickening to thinning under compression Units? Widen 0. 1 cm when compressed by 1 cm Dimensionless Most geologic materials have 0. 1 -0. 4 Rare = -0. 1 Sandstones, change the packing of sand grains May result in tension cracks around new structures

Soils I. Importance for Environmental Science A. Affects plant cover

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content II. Definition – varies by discipline

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content II. Definition – varies by discipline A. Any loose surface material

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content II. Definition – varies by discipline A. Any loose surface material B. Something tillable

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content II. Definition – varies by discipline A. Any loose surface material B. Something tillable C. Any loose surface material from rock weathering and/or organic matter

Soils I. Importance for Environmental Science A. Affects plant cover B. Directly affect runoff, groundwater storage, infiltration rates B. Strength/stability of soils is affected by water content II. Definition – varies by discipline A. Any loose surface material B. Something tillable C. Any loose surface material from rock weathering and/or organic matter D. 3 components – Solids (weathered rock and organics), vapor (atmosphere, gas released from geosphere, gas from the soil itself including water vapor, decomposition and living organisms) and liquids (water, organics, human origin)

Soils III. Soil Horizons A. Layering within a soil unit

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material)

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material) A horizon – organics and weathered rock material

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material) A horizon – organics and weathered rock material E horizon – zone of leaching (zone where water has carried away leachable (mobile) ions and organics)

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material) A horizon – organics and weathered rock material E horizon – zone of leaching (zone where water has carried away leachable (mobile) ions and organics) B horizon – zone of accumulation Bt – argillic (clay) – clays enriched in cations from E Bk – carbonate (Ca. CO 3) enriched zone

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material) A horizon – organics and weathered rock material E horizon – zone of leaching (zone where water has carried away leachable (mobile) ions and organics) B horizon – zone of accumulation Bt – argillic (clay) – clays enriched in cations from E Bk – carbonate (Ca. CO 3) enriched zone C horizon – partially weathered bedrock

Soils III. Soil Horizons A. Layering within a soil unit O horizon – organic zone (decomposing plant material) A horizon – organics and weathered rock material E horizon – zone of leaching (zone where water has carried away leachable (mobile) ions and organics) B horizon – zone of accumulation Bt – argillic (clay) – clays enriched in cations from E Bk – carbonate (Ca. CO 3) enriched zone C horizon – partially weathered bedrock R horizon - bedrock

Soils B. What determines the thicknesses and development of soils horizons?

Soils B. What determines the thicknesses and development of soils horizons? 1. Climate – determines plants growth, leaching rates, weathering rates

Soils B. What determines the thicknesses and development of soils horizons? 1. Climate – determines plants growth, leaching rates, weathering rates 2. Type of rock – determines ions present, ease of weathering

Soils B. What determines the thicknesses and development of soils horizons? 1. Climate – determines plants growth, leaching rates, weathering rates 2. Type of rock – determines ions present, ease of weathering 3. Slope – affects infiltration and stability of organics and rock particles

Soils B. What determines the thicknesses and development of soils horizons? 1. Climate – determines plants growth, leaching rates, weathering rates 2. Type of rock – determines ions present, ease of weathering 3. Slope – affects infiltration and stability of organics and rock particles 4. Others?

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US)

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US) Some organics (not as much as tropics) – good O and A horizons

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US) Some organics (not as much as tropics) – good O and A horizons Some leaching – E horizon develops – Al content is high in this layer because it is not mobile

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US) Some organics (not as much as tropics) – good O and A horizons Some leaching – E horizon develops – Al content is high in this layer because it is not mobile Clay development (weathering of silicate and carbonate rocks (most common rock types) in the

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US) Some organics (not as much as tropics) – good O and A horizons Some leaching – E horizon develops – Al content is high in this layer because it is not mobile Clay development (weathering of silicate and carbonate rocks (most common rock types) in the presence of water creates clays) – B horizon C and R also present

Soils C. Affect of climate 1. Cool/Wet Climates (eastern US) Some organics (not as much as tropics) – good O and A horizons Some leaching – E horizon develops – Al content is high in this layer because it is not mobile Clay development (weathering of silicate and carbonate rocks (most common rock types) in the presence of water creates clays) – B horizon C and R also present Pedalfer soils – Ped = soil, Al = aluminum

Soils 2. Warm/Wet Climates (tropics)

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon Red (iron oxide) and orange (aluminum oxide) rich

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon Red (iron oxide) and orange (aluminum oxide) rich Plants don’t waste energy putting roots into such nutrient poor horizons – shallow, wide root systems

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon Red (iron oxide) and orange (aluminum oxide) rich Plants don’t waste energy putting roots into such nutrient poor horizons – shallow, wide root systems Extensive clay development– B horizon

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon Red (iron oxide) and orange (aluminum oxide) rich Plants don’t waste energy putting roots into such nutrient poor horizons – shallow, wide root systems Extensive clay development– B horizon C and R also present

Soils 2. Warm/Wet Climates (tropics) Much organics – Thick O and A horizons Much leaching – Massive E horizons – very depleted in nutrients High temps speed up oxidation reactions – aluminum- and iron-oxides prevalent in E horizon Red (iron oxide) and orange (aluminum oxide) rich Plants don’t waste energy putting roots into such nutrient poor horizons – shallow, wide root systems Extensive clay development– B horizon C and R also present Laterite soils