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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.

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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

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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

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1 Water and wind erosion

Erodibility of soil

Unsheltered distance

Vegetative cover

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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.