Soil Formation and Mass Movements
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Transcript of Soil Formation and Mass Movements
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Soil Formation and
Mass Movements
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Bellwork:Pg. 143-145
How does water cause mass movements?
How do earthquakes cause mass movements?
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Soil Formation:
Climate determines
soil formation
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Soil Formations1.Tropical Climate2.Dry Climate3.Temperate Climate
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Tropical• Tropical (wet and
warm) Climates make Laterite soils that are thick and infertile
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1. TropicalRain washes away the A Horizon, but rotting vegetation covers the B Horizon
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Laterite
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2. Desert•Desert (Dry) climates make soils from mechanical weathering•Soil is thin and mostly of parent rock (regolith)
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3. Temperate• Temperate (cool to warm) climates make 2 soils that depend on rainfall.• Rain fall is not excessive
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a. Pedalfer Soils – more than 65 cm of rain per year ex: clay, quartz, iron
b. Pedocal Soils –less than 65 cm of rain per year
ex: calcium carbonate
3. Temperate
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Pedalfer
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Pedocal
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Mass Movements Definition• The transportation of
rock and soil down slope due to gravity
•Talus: a pile of rock fragments that accumulates at the base of the slope
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•Together, weathering and mass movements
produce most landforms
•Streams and valleys are the most
common landforms on earth
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• Why?
• Most mass movements end up in a stream or valley
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1.Water – heavy rain and snow saturate the ground
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2. Oversteepened Slopes – angles 25 to 40 degrees will hold loose particles. If a slope is steeper than 40 degrees, slips become more likely.
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3. Removal of Vegetation – plant roots attempt to stabilize
4. Earthquakes
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Mass movements are based on 3 things:
1.Type of material that moves
2.How it moves3.Speed of movement
Classification of Mass Movements
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Types of Mass Movements…
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1. Rockfall: rocks or fragments fall freely through the air =fast movement•Common on steep slopes & can trigger other mass movements
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2. Slide: material moves suddenly along flat, inclined surface
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Rockslide: slides including segments of bedrock
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Slumgullion landslide
Hinsdale County, Colorado700 years old and still moving
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3. Slump: downward movement of material along a curved surface•Leaves a crescent-shaped cliff
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A slump is a type of slope failure which involves the rotational movement of soil or rock
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4. Flows: materials containing large amounts of water
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Earthflow – moves slowly
Mudflow – moves quickly
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5. Creep: slowest type of mass movement. (freezing & thawing)
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