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15 Cards in this Set

  • Front
  • Back
processes that decompose rocks into sediments
Mechanical (physical) weathering – physical disintegration without chemical change
2 types of weathering
Mechanical (physical) weathering – physical disintegration without chemical change
Chemical weathering – reaction with air/water creates a product different physically and chemically
Mechanical Weathering
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
Chemical Weathering
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)
Soil: Regolith
Regolith – surface layer of loose rock, sand, clay
Components of Soil
Components of soil – mineral grains (clay, silt, sand, rock fragments), organic matter, water, gas
– organic debris on the ground’s surface
Humus – decomposed litter, increases water-holding capacity
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
Soil forming factors
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
Weathering decomposes – erosion moves things
Sliding downhill
Moving water
Mass wasting – downslope movement of Earth material under influence of gravity
Landslide – general term for the process and landforms created
Gravity + unstable slope material
Why do landslides occur?
Steepness of slope
Type of rock & orientation of rock layers
Nature of unconsolidated material
Water and vegetation
Earthquakes and volcanoes
types of landslides
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
Predicting and avoiding landslides
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