3.2.5.2 causes of soil and soil degradation

what is wind erosion?

dry soil or low clay content soil is loose

Due to little cohesion between particles

If it's windy + unprotected it blows
away

what problems can wind erosion cause?

soil deposited over crops /urban areas

Name an event caused wind erosion

1937 dust bowl catastrophe in the
USA.

What is rain splash erosion?

· raindrop splash dislodges soil particles

· soil particles dispersed everywhere

those going downhill travel further

causes downhill movements of
large amounts of soil

surface runoff erosion

infiltration capacity exceeds causes surface run off

occurs during heavy rain or when soil is impermeable

slumping and landslides

increased mass + lubrication from water

causes downward movement of large amounts of soil

occurs when soil on steep slope is less
stable due to deforestation
↳ roots decompose + soil particles
loosen

What is all water erosion increased by?

Steeper gradient

What are the types of erosion?

Wind
Water (surface runoff, rain splash, slumping)

How does vegetation reduce soil erosion?

• natural windbreak by reducing velocity & kE to carry particles

• leaf litter reduces impact of raindrop splash so particles dislodged less

• DOM (colloidal material humus) bind particles

• plant roots hold soil together

• increase infiltration & reduces surface runoff & therefore reduces erosion

What are human activities that increase the rate of soil erosion?

Overgrazing
Ploughing of vulnerable soils
Reduced soil biota
Soil compaction
Cultivating steep slopes

how does soil compaction increase soil erosion?

· use of heavy machinary, high livestock density + lack of detrivores cause compaction

small interstitial spaces reduce infiltration + drainage rates

↑ surface runoff so increases erosion

how does overgrazing increase erosion?

vegetation eaten faster than it can grow

increases soil exposure & erosion

damage by hooves

cultivation of steep slopes

surface runoff flows more rapidly
So more kE to pickup + carry particles

· increases ploughing risk as it disturbs soil

how does reduced biota increase soil erosion?

ploughing, less organic matter, + agrochemicals reduce number of living organisms in the soil.

Less dead organic matter is broken down.

So less humus is formed and doesn't hold soil particles together.

how does ploughing vulnerable soils increase SE?

breaks up soil structure, exposing
soil particles to erosion by water
or wind

how does removing vegetation increase soil erosion

removing vegetation removes protection from erosion

increased atmospheric particulates

wind erosion causes atmospheric particulates

Causes health problems

How is desertification an impact of erosion?

makes it more difficult for vegetation to grow
· further soil erosion and less rainfall
1/3 agricultural soils lost in the past 40 yrs