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15 Cards in this Set
- Front
- Back
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Weathering
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processes that decompose rocks into sediments
Mechanical (physical) weathering – physical disintegration without chemical change |
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2 types of weathering
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Mechanical (physical) weathering – physical disintegration without chemical change
Chemical weathering – reaction with air/water creates a product different physically and chemically |
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Mechanical Weathering
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Pressure release fracturing – formerly buried rocks expand when uncovered
Frost wedging – water in cracks expands when frozen Abrasion – rock particles moving in contact wear each other away Organic activity – roots Thermal expansion / contraction |
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Chemical Weathering
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Dissolution – many minerals dissolve to some degree
Hydrolysis – reaction with water, new mineral forms Oxidation – reaction with oxygen, new mineral forms Chemical & mechanical weathering together Salt cracking – salts dissolve out of minerals, recrystallizes in rocks when water evaporates, creates pressure Exfoliation – granite sheets peel off rock due to hydrolysis expansion (clays form and swell up) |
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Soil: Regolith
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Regolith – surface layer of loose rock, sand, clay
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Components of Soil
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Components of soil – mineral grains (clay, silt, sand, rock fragments), organic matter, water, gas
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Litter
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– organic debris on the ground’s surface
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Humus
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Humus – decomposed litter, increases water-holding capacity
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Horizons
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Horizons – soils develop a layered structure, the layers are called horizons; (from top)
O horizon – mostly litter and humus A horizon – mixture of humus, sand, silt, clay O + A = topsoil B horizon – subsoil, low organics C horizon – partially weathered rock Water moves through soil and leaches ions Water, ions, clay from “A” end up in “B |
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Soil forming factors
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Soil forming factors
Parent rock – texture and composition Climate – rainfall and temperature Capillary action Pedocal – salt-encrusted soil particles Caliche – calcite that forms soil cement Salinization – dissolved ions left behind after evaporation (problem in irrigated lands) Pedalfer – clay-rich subsoil |
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Erosion
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Weathering decomposes – erosion moves things
Sliding downhill Moving water Wind |
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Landslides
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Mass wasting – downslope movement of Earth material under influence of gravity
Landslide – general term for the process and landforms created Gravity + unstable slope material |
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Why do landslides occur?
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Steepness of slope
Type of rock & orientation of rock layers Nature of unconsolidated material Water and vegetation Earthquakes and volcanoes |
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types of landslides
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Flows – particles move independent of each other
Creep – slow movement, often of unconsolidated sediment (soil creep) Debris flow – more than ½ the particles larger than sand sized, speed varies Earth/mud flow – movement of fine-grained particles and water Slide – material moves as a coherent mass Slump – downward slipping of Earth materials, usually involves a rotation on concave surface Rockslide – generally rapid movement of detached bedrock Fall – material free falls Very steep slopes, cliffs |
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Predicting and avoiding landslides
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Commonly occur in same area
Thus a slide on one slope could mean other, nearby slopes could fail Pattern of human settlement often didn’t / doesn’t take hazard evaluation into account Building codes & practices |
