Comparing the recent basaltic
soils of parts of NSW with
deeply weathered soils of
Western Australia
Australian soils tend to be:
• Old
• Salty
• clayey - except in the west of the continent
where they tend to be sandy
• Acidic
• nutritionally and organically impoverished
• structurally challenging
Basaltic soils of East Coast
• Pockets of recently formed
basaltic soils exist in parts
the East Coast of Australia.
• Recent volcanic activity oldest extinct volcano found
in Northern Queensland 33
mil yrs oldn Youngest in
Victoria 10 mil yrs old
(Australia moved over
hotspot)
• Eg Mt Warning Tweed
Coast is a remnant of a
volcano that spewed lava
around 20 million years
ago.
Australian plate is moving North at around 7cm per yr
Basaltic Soil
• Parent rock basalt
(mafic)
• Fine textured
• Deep red/ chocolate
colour
• High in nutrients (high
level of calcium
phosphate which acts
like fertilizer)
• Very fertile
Deeply weathered laterite
soils of Western Australia
• Parent rock generally
granite (felsic)
• Laterite (soil residue
composed of secondary iron
oxides)
• Coarse texture
• Old (long time of
weathering, leaching)
• Nutrient poor
• Colour red (due to oxidation
of iron)
• Rich in Aluminium and Iron
• Australian soils have been subject to extensive
degradation due to such practices as;
overgrazing, over cultivation, tree clearing,
and irrigation.
• A continuous cover of vegetation on the soil
results in the most stable situation. However
this is not possible for many land uses,
particularly those in the agricultural sector.
• Major forms of degradation:
wind and water erosion
reduced fertility because of nutrient loss physical
breakdown of soil structure soil
acidification
salinisation
Soil Erosion
Is the movement of particles
Of soil, surface sediments
and rocks by the action of
water, glaciers, winds, waves
and so on
Wind erosion
Sheet erosion
• Removal of uniform layer of soil over a wide area.
Usually caused by rainfall (rain drop splash)
• Removes the top soil layer (bulk of nutrients)
Rill Erosion
• Numerous small channels
Gully Erosion
Removal of soil by a concentrated flow
Of water with a sufficient velocity to cut
Large channels