Differentiate between natural soil erosion and soil erosion
caused by humans List the main causes of accelerated erosion List
and define the major types of soil erosion
Slide 3
Natural process that occurs all the time Part of the soil
formation process Much slower than soil formation
Slide 4
A speed up of the normal rate of erosion Begins when lands
natural plant cover is removed Caused by two basic forces-moving
water and wind
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Slide 6
Occurs when raindrops strike the earth Raindrops hit at about
20 MPH If raindrops strike plants their force is broken and they
become harmless If raindrops strike bare soil the force is absorbed
by soil particles and they are torn apart When this happens the
soil particles are either suspended and carried away or filter into
soil pore spaces making the soil less permeable.
Slide 7
Most destructive action of water on soil The faster the water
flows the more destructive it becomes Three-fold damage Existing
soil structure is damaged Soil surface is reshaped making it less
workable Soil is carried away and may eventually be redeposited
elsewhere Silt deposits can sometimes be good Nile Valley,
Mississippi Delta Most are harmful causing clogged waterways, fish
kills, filled lakes, muddy streams and mud flats
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Slide 10
2 basic actions-drying and dislodging, movement A serious
problem in dry areas where the land is relatively flat with few
trees
Slide 11
Dries the soil surface Moves soil particles leaving behind
larger sand particles making soil surfaces become very sandy or
covered by a layer of clay
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Slide 13
Gradual and fairly uniform removal of the surface soil Occurs
slowly so producer may not even be aware it is taking place Caused
by splash erosion coupled with a slow runoff of soil-laden
water
Slide 14
Gradual reduction of the topsoil thickness This leads to a
decrease in soil productivity and eventually totally unproductive
soil Also notice color changes in the soil in plowed fields because
as they are plowed subsoil is brought to the top Discoloration is a
indication that sheet erosion is well advanced and damage has
already been done
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Slide 16
More rapid and visible Rills are small streams cut into the
soil surface by running water Damage has occurred when rills appear
May be very small or large and noticeable When rills become too
large they become a gully
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Slide 18
Obvious Severe problem More obvious than rill or sheet
erosion
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Slide 20
2 forms of damage Soil removal Sand deposits or drifts
Slide 21
Much like sheet erosion Wind simply picks up the soil particles
and blows them away As soil blows away The field becomes less
productive It retains less rainwater It produces less vegetation
Damage may be severe before it becomes obvious
Slide 22
Slide 23
More obvious Result when the wind is forced to change
directions abruptly Fencerows, windbreaks, sides of buildings When
the wind changes direction it redeposit's the soil particles Larger
and more flat bare fields are the more likely they will be affected
by wind erosion
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Watch Modern Marvels: Black Blizzard and complete
questions