ENV 101 Ch10 lecture ppt_a
- 1. 10-1 Environmental Geology James Reichard Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
- 2. 10-2 Chapter 10 Soil Resources © Glow Images
- 3. 10-3 Soil loss (1) If left unchecked, soil loss will ultimately lead to a reduction in worldwide food production. Tim McCabe, USDA Natural Resources Conservation Service Jump to long description
- 4. 10-4 Formation of Soils (1) • Bedrock • Regolith • Sediment Howard Woodward, Plant Science Department, South Dakota State University Jump to long description
- 5. 10-5 Formation of Soils (2) Weathering • Physical • Chemical • Quartz resistant to chemical weathering A. Stone Mountain, Georgia B. Grand Canyon, Arizona (a-b): © Jim Reichard Jump to long description
- 6. 10-6 Soil Horizons Jump to long description
- 7. 10-7 Soil Color (a-b): Jim Fortner, USDA-NRCS Jump to long description
- 8. 10-8 Soil Texture Jump to long description
- 9. 10-9 Soil peds (1) Jump to long description
- 10. 10-10 Soil peds (2) Soil forming factors: Clorpt… •Climate •Organisms •Relief (topography) •Parent material •Time •…other factors (e.g., dust)
- 11. 10-11 Sources of Parent Material Jump to long description
- 12. 10-12 Influence of the Parent material Jump to long description
- 13. 10-13 Influence of Organisms Jump to long description
- 14. 10-14 Influence of Topography (relief) Jump to long description
- 15. 10-15 Paleosol b: © Jukka Käyhkö, University of Turku Jump to long description
- 16. 10-16 Soil Components Jump to long description
- 17. 10-17 Soil orders in North America Soil taxonomy is based on the characteristics of the horizons found in a particular soil as well as the soil's temperature and moisture regime. Jump to long description
- 18. 10-18 Scientists and engineers classify soils in different ways. • To scientists, soil is considered to be the narrow zone of fragmental material near the surface where physical and chemical processes have created soil horizons. • Engineers simply view soil as any type of fragmental earth material (i.e., nonbedrock), which is what geologists refer to as sediment (transported) or regolith (untransported). • Soils are classified based primarily on the proportion of gravel, sand, silt, and clay- sized particles.
- 19. 10-19 Soil Properties • Porosity • Soil moisture & drought resistance • Permeability • Strength & sensitivity • Plasticity • Compressibility • Shrink-swell • Ion exchange capacity
- 20. 10-20 Cohesive force Jump to long description
- 21. 10-21 Soil compaction c: © Goodshoot/Fotosearch Jump to long description
- 22. 10-22 Expanding clay © Paul McDaniel, University of Idaho a (top): Colorado Geological Survey/Photo by David Noe; (bottom): P. Camp, USDA-NRCS Jump to long description
- 23. 10-23 Soil Ions Jump to long description
- 24. 10-24 Soil as a Resource Agricultural food production • Soil fertility • Essential nutrients Minerals and energy • Aluminum • Kaolinite clay • Peat b: Lynn Betts, USDA Natural Resources Conservation Service Jump to long description
- 25. 10-25 Bauxite Jump to long description
- 26. 10-26 Peat Cynthia Stiles, USDA-NRCS Jump to long description
- 27. 10-27 Soil Loss (2) Soil erosion • Natural • Man-made Consequences USDA Jump to long description
- 28. 10-28 Construction and soil loss (1) At a site in the eastern United States Jump to long description
- 29. 10-29 Construction and soil loss (2) USDA Jump to long description
- 30. 10-30 Soil Loss (3) Mitigation • Contour plowing • Crop stripping • No till farming • Grassed waterways • Terracing • Stream buffers • Silt fences • Retention basins • Slope vegetation cover © Doug Sherman/Geofile Jump to long description
- 31. 10-31 Construction and soil loss (3) A. Southwest Iowa B. Iowa-Minnesota border (a-b): Tim McCabe, USDA Natural Resources Conservation Service A. Ionia Country, Michigan B. Missouri (a-b): Fred Gasper, USDA Natural Resources Conservation Service Jump to long description
- 32. 10-32 Construction and soil loss (4) © PhotoLink/Getty Images Story Country, lowa Lynn Betts, USDA Natural Resources Conservation Service Jump to long description
- 33. 10-33 Silt fences and retention basins A. George L. Smith State Park, Georgia © Jim Reichard Jump to long description
- 34. 10-34 Dust Bowl b: USDA Natural Resources Conservation Service Jump to long description
- 35. 10-35 Salinization of Soils Ron Nichols, USDA Natural Resources Conservation Service Jump to long description
- 36. 10-36 Hardpans Parent Material Jump to long description
- 37. 10-37 Thawing Permafrost Joe Moore USDA-NRCS Jump to long description
- 38. Appendix of Image Long Descriptions
- 39. Soil loss (1) Long Description Photo showing water carrying valuable topsoil off a farm field in Tennessee after a heavy rain. Agricultural activity commonly leads to increased erosion and a net loss of soil because row crops offer far less protection against falling raindrops and flowing water compared to natural vegetation. If left unchecked, soil loss will ultimately lead to a reduction in worldwide food production. Jump back to slide containing original image
- 40. Formation of Soils (1) Long Description Photo showing a soil that developed from the breakdown of the underlying rock into individual particle grains. Notice how the soil covers the landscape as a thin blanket of loose weathered material, which geologists refer to as regolith. Jump back to slide containing original image
- 41. Formation of Soils (2) Long Description Photo (A) showing a bowl-shaped depression in solid granite that has been filled with soil formed from the weathering of the rock itself. The roots of the tree in (B) have grown into fractures within the rock, extracting moisture and nutrients from soil within the cracks. Jump back to slide containing original image
- 42. Soil Horizons Long Description A time sequence illustrating the order in which soil horizons will develop when granite bedrock becomes exposed to weathering processes on Earth’s surface. Notice how clay minerals, dissolved iron, and other elements are carried downward with infiltrating water and then accumulate in the B horizon. Jump back to slide containing original image
- 43. Soil Color Long Description Soil horizons commonly have distinct colors due to the presence or absence of pigments. The organic content of the A horizon in (A) gives it a black color, which is in marked contrast to the C horizon that is light colored because it lacks pigments. The older, more developed profile in (B) shows a much thicker A horizon that overlays a B horizon that is reddish in color due to the presence of iron-oxide minerals. Jump back to slide containing original image
- 44. Soil Texture Long Description Scientists break soils down into 12 textural classes based on the percentages of sand, silt, and clay-sized particles. Texture is important because it helps determine the drainage and fertility characteristics of a soil. Note that soil scientists define the size range for sand, silt, and clay differently than do geologists. Jump back to slide containing original image
- 45. Soil peds (1) Long Description Illustration showing various shapes of soil peds (aggregates). The size and shape of peds determine a soil’s structure and influence root development and infiltration of water. Jump back to slide containing original image
- 46. Sources of Parent MaterialLong Description Illustration showing how some soils form on parent material that is derived from weathering of the underlying bedrock, whereas other soils form on transported sediment that bears no relationship to the bedrock. Soils that form on river-transported material are commonly quite fertile due to the abundance of organic matter that grows under the moist conditions and is also deposited during periodic floods. Jump back to slide containing original image
- 47. Influence of the Parent material Long Description Because rocks contain assemblages of minerals, the weathering of different rock types can produce parent material with varying proportions of quartz and clay minerals. This variation causes residual soils to differ in their drainage and water storage properties, ultimately leading to the preferential growth of different plant communities. Jump back to slide containing original image
- 48. Influence of Organisms Long Description Soil can be thought of as a living system, supporting life both on the surface and in the subsurface. Organisms aid in soil development by adding organic matter, overturning the soil, and providing passageways for air and water. Jump back to slide containing original image
- 49. Influence of Topography (relief) Long Description Soils on topographically high areas generally contain less organic matter because of better drainage and higher rates of decomposition. Soils in low areas commonly have more organic material due to more lush vegetation and poorer drainage, which tends to preserve organic matter. On steeper portions of a slope, soils are thinner due to the higher rates of erosion. Jump back to slide containing original image
- 50. Paleosol Long Description Illustration (A) showing how a paleosol forms when new sediment is deposited over an existing soil sequence, creating an important time marker that can be dated by carbon-14 radiometric dating. Photo (B) shows a paleosol in Finland that formed when wind-blown sand was deposited over the existing landscape. Jump back to slide containing original image
- 51. Soil Components Long Description Soils consist of about 45% mineral matter and 5% organics, with the remaining 50% being void space that is filled with air and water. Within the pores, dipolar water molecules are strongly attracted to the extremely small clay-mineral particles, whose crystal structure results in negative charges on their outer surfaces. Jump back to slide containing original image
- 52. Soil orders in North America Long Description Map showing the distribution of soil orders in North America. Many of the patterns shown here are related to variations in climate and geologic history, both of which strongly influence soil formation. Jump back to slide containing original image
- 53. Cohesive force Long Description Illustration showing how a water droplet is composed of individual water molecules that are attracted to one another by cohesive forces. The droplet is attached to the ceiling by adhesive forces that exist between the solid surface and the water molecules. Additional water molecules will cause the droplet to grow in size until gravity overcomes the cohesive forces, at which point the droplet will fall. These same forces operate in soils and control the ability of water to flow through the pore spaces. Jump back to slide containing original image
- 54. Soil compaction Long Description When a heavy load is applied to a soil, the individual grains will attempt to rearrange into a more tightly packed configuration. Sandy soils (A) have low compressibility because the reduction in volume that can occur when rounded grains are rearranged is relatively small. Clay-rich soils (B) are highly compressible because the random orientation of small clay particles allows for a significant reduction in volume. The uneven settling of the Leaning Tower of Pisa (C) was caused by differences in compaction that were related to variations in the clay content of the soils. Jump back to slide containing original image
- 55. Expanding clay Long Description a) The number of water molecules that can be held within the sheetlike structure of clay minerals varies among different types of clays. Expanding clays have a great capacity to take on water, causing soils called vertisols to increase in volume. When vertisols are allowed to dry, they shrink considerably, creating cracks, like those in the dried-out lake bed shown in this photo—note the yellow camera for scale. b) Soils known as vertisols contain significant amounts of expanding clays, which can cause serious structural damage should the soil go through repeated drying and wetting cycles. Photos (A) illustrate the types of damage that can occur when the underlying soil expands and contracts. Map (B) showing areas in the United States where soils have a high swelling potential. Jump back to slide containing original image
- 56. Soil Ions Long Description a) Positively charged ions naturally attach themselves in a layer (A) around the negatively charged surfaces of particles of clay minerals and organic matter within a soil. Notice how negative ions surround the positive ions. As percolating water (B) carries ions through the soil, they selectively exchange with the ions already attached to the soil particles. The actual exchanges that occur depend on the attraction and concentration of ions in the percolating water. b) Young soils commonly have an abundance of rock and mineral fragments, which weather and produce dissolved ions that are essential for plant growth. These nutrients attach themselves to clay minerals and eventually exchange with hydrogen ions in rainwater, making it less acidic. In older soils few fragments remain to be weathered, and thus fewer nutrients are produced. Percolating rainwater then remains acidic since the ion exchange sites are occupied by nonessential elements and hydrogen ions, rendering the soil infertile and acidic. Jump back to slide containing original image
- 57. Soil as a Resource Long Description Generalized map (A) showing the different amount of organic matter (metric tons per hectare) in soils in the United States. Regional differences are strongly related to climate, vegetation types, and amount of weathering. Photo (B) showing the high organic content of an exceptionally fertile topsoil in Iowa. Jump back to slide containing original image
- 58. Bauxite Long Description Economical deposits of bauxite form when feldspar-rich igneous rocks undergo long periods of intense chemical weathering. As the aluminum-rich feldspar minerals are transformed into clay minerals, the percentage by weight of aluminum in the minerals increases. Over time this process creates a bauxite deposit containing minerals that are highly enriched in aluminum. Jump back to slide containing original image
- 59. Peat Long Description Organic-rich soil, known as peat, forms in bogs where it can be extracted and dried, then used as a fuel for heating and cooking. Peat is also used as gardening mulch and in potting soils. The photo is from a bog in Scotland. Jump back to slide containing original image
- 60. Soil Loss (2) Long Description The impact of raindrops on an unprotected soil creates an explosive effect that preferentially ejects clay and organic particles onto the surface. Soil erosion occurs when the loose particles are transported by wind or water moving downslope as overland flow. Over time this process reduces soil fertility. Jump back to slide containing original image
- 61. Construction and soil loss (1) Long Description Graph showing how sediment loss changed over time in response to different land uses at a site in the eastern United States. Note the significant increases in soil loss that accompanied changes to agriculture and a construction boom. Jump back to slide containing original image
- 62. Construction and soil loss (2) Long Description Map showing the estimated average rate of soil loss per acre on agricultural land in the United States. Variation in soil loss is largely due to the level of agricultural activity and the steepness of the terrain. Jump back to slide containing original image
- 63. Soil Loss (3) Long Description Rather than plowing the remains of the previous crop into the soil, in no-till farming the residue is left in place to help shield the soil from the direct impact of raindrops. Jump back to slide containing original image
- 64. Construction and soil loss (3) Long Description Contour plowing (A) involves planting rows parallel to the slope of the land, reducing overland flow and soil erosion. In strip cropping (B) different crops are planted in alternate strips to trap sediment moving downslope—note in the photo how strip cropping is combined with contour plowing. Overland flow naturally collects in the low areas or swales of a field and leads to the formation of gullies (A) in the exposed soil, creating obstacles for farm machinery and reducing crop production. Planting grass in the swales rather than crops (B) prevents the formation of gullies. Jump back to slide containing original image
- 65. Construction and soil loss (4) Long Description Terracing allows agriculture to take place on steep hillsides that would otherwise be impossible to cultivate due to severe soil erosion. Note how the rice fields shown here follow the contours of the land surface. Stream buffers reduce sediment pollution by trapping sediment moving off adjacent fields before it can enter the drainage system. Most stream buffers consist of a combination of grass strips and uncut forest along stream channels. Jump back to slide containing original image
- 66. Silt fences and retention basins Long Description Properly installed silt fences (A) help prevent sediment pollution by keeping sediment at construction sites from entering a drainage network. Retention basins (B) are used to collect or trap sediment before it can enter a stream channel. Farmers also use retention basins to collect valuable topsoil coming off their fields. Jump back to slide containing original image
- 67. Dust Bowl Long Description Map showing the area known as the Dust Bowl that was affected by severe wind erosion and soil loss during the 1930s (B). The result was a collapse of local farm economies Jump back to slide containing original image
- 68. Salinization of Soils Long Description Irrigating poorly drained desert soils that naturally contain mineral salts often leads to salinization. Poor drainage allows the irrigated water to accumulate and dissolve the salt minerals. The resulting saline water then moves up into the root zone, reducing crop production. Jump back to slide containing original image
- 69. Hardpans Long Description A hardpan is a soil layer rich in clay or one cemented together by minerals, making it difficult for roots or water to penetrate the soil. Plants are then forced to have shallow root systems, making them more susceptible to wilting during droughts, and drowning during wet periods. When planting trees or shrubs, it is best to dig through the hardpan to provide better drainage and more room for root growth. Jump back to slide containing original image
- 70. Thawing Permafrost Long Description Construction of this highway in Alaska caused a portion of the underlying permafrost to thaw, creating a subsurface void that then collapsed into a sinkhole. Damage caused by human-induced melting of permafrost is common in polar regions. Jump back to slide containing original image