Topic 8: Soil Erosion Flashcards
(48 cards)
What is soil erosion?
A natural process where soil particles are removed by wind or water
What is the rate of soil erosion like in sois that haven’t been affected by human activity?
The same as the rate of soil formation
When is soil erosion an issue?
When the rate is faster than that of soil formation
Name the 2 types of soil erosion
Wind erosion
Water erosion
When is soil most vulnerable to wind erosion?
When it is a dry soil or has a low clay content
This is because they are likely to be loose and there is little cohesion between the particles that would hold the soil together
So the soil blows away
Where is wind erosion a problem?
In the area where the soil has been removed
In the area where the soil is deposited- it may cover crops or land in urban areas
Name the types of water erosion
Rain splash erosion
Surface runoff erosion
Slumping and landslides
What increases all forms of water erosion?
Steeper gradients
Rain splash erosion
When soil particles are dislodged by a rain droplet
Soil particles are dispersed in different directions
Those going downhill are more likely to go further
Surface runoff erosion
Caused when the infiltration capacity of the soil has been exceeded
Can occur in heavy or prolonged rainfall or if soil is impermeable
Leads water to flow over the ground surface
Slumping and landslides
When soil on slopes becomes wet, increased mass and lubrication of water makes it more likely that large amounts of soil will move downwards
Often occurs when deep soil on slopes becomes less stable because of deforestation
Why are landslides more common because of deforestation?
The roots of trees that held the soil together decompose
The soil isnt held together as strong
Landslides are more likely after heavy rain
What areas are susceptible to both types of soil erosion?
Areas with seasonal rainfall, like Sub-Saharan Africa
Why may areas like sub-Saharan Africa suffer from both types of soil erosion?
Wind erosion in the dry season
Rainfall erosion in the wet season
How does vegetation reduce the rate of soil erosion?
-it acts as a natural windbreak, reduces wind velocity/kinetic energy that could carry away soil particles
-that and leaf litter reduce the impact of raindrops-soil particles are less likely to be dislodged
-soil organic matter helps to bind soil particles together
-plant roots hold the soil together
-plants held infiltration of water into soil high reduces the rate of runoff, reducing water erosion
What human activities increase the rate of soil erosion?
Vegetation removal
Ploughing vulnerable soils
Overgrazing
Reducing soil biota
Soil compaction
Cultivating steep slopes
How can vegetation removal increase soil erosion?
Removes protection from erosion
How can ploughing vulnerable soils increase soil erosion?
It breaks up soil structure
Soil particle are exposed to erosion as a result of
how can overgrazing increase soil erosion?
Vegetation eaten faster than it can grow
Soil is exposed to erosion
Disturbance & root damage by hooves can increase erosion risk
How can reducing soil biota increase soil erosion?
Less dead organic matter is broken down
How does soil compaction increase soil erosion?
Use of heavy machinery
Reduction in soil detrivores
Makes smaller interstitial spaces which reduces the infiltration rate
How does cultivating steep slopes increase soil erosion?
Surface runoff water flows more rapidly down steeper slopes
More kinetic energy to pick up more soil particles
Ploughing e.g. adds to erosion risk
What are the affects of accelerated soil erosion?
Reduced productivity
Sedimentation in rivers & reservoirs
Increased atmospheric particulates
Desertification
How is productivity reduced because of accelerated soil erosion?
Fertile top soil is usually what is eroded
Remaining soil will be less fertile
Plant growth is reduced
Smaller harvests
Shallower soil may also make root penetration difficult
