Geography Reference
In-Depth Information
worsens the situation. In some countries around 10 per cent of
their arable land is affected by salinisation.
The above human impacts on soils have led to concerted efforts,
legislation and policy to protect and restore soils as an important
underpinning resource for human life. However, much more effort
is needed particularly as the world's population continues to grow,
placing more demand on our soil resource.
SUMMARY
• TheEarthis4.6billionyearsold.
• TheEarth'scrustisformedofmovingplates;attheedgesof
plates earthquakes and volcanic activity are common.
• Ascontinentscollidemountainsform.
• Inthecentreofoceansnewcrustisformed;attheedgeofoceans
the crust sinks back into the mantle. Ocean crust is relatively
young being less than 200 million years old whereas continental
rocks can be billions of years old.
• Weatheringbyphysicalandchemicalprocesseswearsdown
rock. Climate and rock type are important controls of weather-
ing process rates.
• Erosiontransportsweatheredmaterialbywater,wind,andslow
and fast mass movement.
• Soilismadeupofmineralsfromweatheredrock,organicmatter
,
water and air.
• Soilformationisaffectedbyclimate,theparentmaterial,topo-
graphy and organisms.
• Thetextureofsoilparticles,structureandchemistryofasoilare
crucial in determining its water and nutrient exchange capacity
and hence its use for plant growth.
• Movementofmaterialsverticallyandlaterallythroughthesoil
dissolved in water is an important process for transferring nutri-
ents for plants and impacting stream water quality.
• Carefulsoilmanagementisrequiredashumanshavedegraded
large areas of soil across the Earth through poor agricultural
practice and pollution.
