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Soils and change
The causes of soil erosion
+Soil erosion
The washing away or blowing away of top soil such that the fertility of the remaining soil is greatly reduced. Soil erosion is most rapid in those areas where there is the misuse of land by people.
+Definitions in this power point
Just so you know:
All of the definitions for this power point were taken from:
‘A-Z Handbook: Geography’ 4th edition. M.Skinner, D.Redfern, G.Farmer.
It is a very useful book, one well worth buying.
+
The causes of soil erosion
Erosion by wind and water
Physical degradation
Chemical degradation
Biological degradation
Climate and land use change
Impact of artificial
fetiliisers and pesticides
Erosion – the removal of weathered material by the action of gravity, water, wind or ice.
Weathering – the disintegration and decomposition of rocks in situ by the combined actions of the weather, plants and animals.
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1 Water and wind erosion
Rainfall intensity and runoff. The impact of raindrops on the soil surface.
Gully and rill erosion
Fine material
Easily moved by rain
splash and runoff water
Greater raindrop energy
required to move…
…larger material – sand and
gravel
+
1 Water and wind erosion
Reduced infiltration (eg from
soil compactio
n, or freezing)
Excess water on a
slope
Increased surface run
off
Agricultural land
Run off greatest in
spring
No vegetation cover and there is
saturated ground
+1 Water and wind erosion
Slope gradient and length
The steeper the slope the greater the loss of soil by erosion
Vegetation
Protects the soil from rain drop splash
Slows down the movement of surface water
+
1 Water and wind erosion
Erodibility of soil
Unsheltered distance
Vegetative cover
+
Physical degradation
Soil compaction caused by
heavy machinery
and animals
Increases surface run
off
Decreases infiltration
Prevent seeding
emergence
+Chemical degradation
Loss of nutrients in the soil can cause acidification – changes the chemical composition of the soil
Acid rain – increased acidity of soil by acids in rain from fossil fuels
Salinisation – occurs in dry (arid) areas. Capillary action draws slats to the surface of the soil. High rates of evaporation removes moisture leaving a slat layer on the surface.
+Biological degradation
Organic matter = plants remains and POO POO.
Loss of organic matter
Reduces stability of the soil
Can lead to the
formation of soil crusts
Reduces infiltratio
n
+Climate and land use change
If the climate change (remember the difference between weather and climate?) – we will have to rethink the way we use our land.
We will have to adapt to new the new conditions whether they are wetter, dryer, colder or warmer.
+The impact of artificial fertilisers and pesticides
If this graph was in a paper one exam. What question would go with it?
It might be something like:
STEMStudy fig.6, it is a graph showing the world consumption of fertiliser 1961-2001. QUESTIONDescribe the pattern of change in fertisier consumption 1961-2001
Of course, you’d remember the rules:
1. Read the stem2. Study whatever it is – labels, key etc.3. Read the question, identify the command word4. Relook at at whatever it is5. Answer the question
6. Describe the main patters7. Use data in your answer8. Any anomalies?
+Additional reading – all on the weebly and all really good!
‘Soil degradation in the UK’ J. Butler, Geography Review, Vol 25, No.3, Feb 2012, p22-25
‘Managing soil erosion: a case study from Ireland’ D.Mullan & D. Favis-Mortlock, Geography Review, Vol 24, No 4, April 2011
‘Soil erosion’ Wide World, Vol 23, No 3, p6-7
Just so you know:
1 – Geography Review is a brilliant magazine. It is aimed at geography students aged 16-18
2 – Wide World is made by the same people but is aimed at students aged 14-16, so their articles are easier but less detailed.