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Weathering, Soil, Mass Movements, Erosion

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Weathering, Soil, Mass Movements, Erosion

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    1. Weathering, Soil, Mass Movements, & Erosion

    2. Weathering

    9. Hydrolysis: Chemical weathering by reaction of water with other substances Minerals (such as feldspar, hornblende, augite) dissolve into ions and react with water to form clay minerals Water’s chemical effects is increased by the presence of acids dissolved in water Water and Chemical Weathering

    11. Pollution Gases: from volcanoes, cars (nitrogen oxides), or power plants (sulfur dioxides) can make rainwater even more acidic (ACID RAIN)

    12. Caves are carved out of limestone as water flows through them

    14. Organic Lichens: fungi + algae that make acids which can dissolve rock

    15. Oxygen and Chemical Weathering

    17. Surface Exposure & Weathering Rate Breaking rocks into smaller pieces exposes more surface area and causes them to weather faster.

    18. Composition of Rock Different types of rocks weather at different rates. Determined by: the rock’s mineral composition type of weathering More resistant (quartz-based) rocks weather slower than less resistant (feldspar, hornblende, biotite mica, augite, calcite, gypsum-based) rocks

    20. Weathering, Soil, Mass Movements & Erosion

    21. What is soil and how does it form? Soil is: the mixture of weathered rock and organic material that covers bedrock and in which plants with roots can grow. typically composed of 3 layers or horizons.

    22. Types of Soils Parent material- the material that soil comes from Residual Soil- parent material is local bedrock (beneath the soil) Transported Soil- formed from parent material in different areas and is brought into an area by wind or water (rivers or glaciers) Most soils in New England are transported soils

    24. Soil Profile A horizon (topsoil) top layer rich in organic remains (humus) gray-black color B horizon (subsoil) middle layer rich in minerals Washed down from A horizon iron, clay, calcium, magnesium red-brown color C horizon lowest layer slightly weathered parent material color depends on parent material

    25. Soil Composition Soil is classified by composition (make up). 1000s of different types Strong link between composition & climate

    26. Weathering, Soil, Mass Movements & Erosion

    27. Mass movements and erosion carry away weathered materials.

    29. Mass Movements Mass movements- Movement of material down slope under the influence of gravity Talus- rock fragments that have been weathered from a cliff and pulled down by gravity Landslide- general name for the movement of a mass of bedrock or loose soil and rock down the slope of a hill, mountain, or cliff Most likely on steep slopes Tend to occur after heavy rains or during the spring when large amounts of snow are melting

    30. Specific types of mass movements Fast moving Flows Earthflows Mudflows Landslides Avalanches Rockslides Slow moving Creep Slump

    31. Creep Very low velocity (slow), gradual, steady movement of surface soil Movement is imperceptible, but effects can be seen Fence posts, poles, & trees to lean downhill

    32. Slump Blocks of land tilt and move downhill along a surface that curves into the slope. Tends to occur because a slope has become too steep for the bottom of the slope to support the soil at the top.

    33. Flows Earthflows: soil saturated with water, flows downhill Slower and less fluid than mudflow Affected by amount of water present, composition of soil, and steepness of the slope Mudflows: rapid movement of water that contains large amounts of suspended clay and silt Can move rocks, boulders, and trees Tend to occur in drier regions that experience infrequent but heavy rains

    34. Landslides/Avalanches & Rockslides High velocity event, material is loose & dry.

    35. Erosion and Landforms Rivers, streams, glaciers, wind, and ocean waves and currents are all agents of erosion. Climate and composition of the rock also play an important role Erosion helps in shaping the landscape Topography depends on the “balance” between uplifting forces and erosion

    36. Soil as a Resource Soil fertility- ability of soil to grow plants Proportion of minerals, water & organic matter determines fertility Threats to fertility: Soil depletion- when nutrients are lacking or taken out of soil to the point where it can no longer grow a usable crop Reduce depletion by allowing field to lay fallow or by rotating crops Often add fertilizers instead Runoff affects ecological balance (ex. water quality) Salinization- water from irrigation leaves behind minerals as it evaporates Eventually, soil cannot support crop growth

    37. Erosion and Soil Conservation

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