What are sub-aerial processes?
Use this Power Point to make notes
about the different types of weathering
& mass movement
What are sub-aerial processes?
The coast is the narrow zone
between the land and the
sea.
It is worth remembering that
the landscape will be
influenced by processes on
the land as well as the sea.
Sub-aerial processes
include weathering and mass
movement. These processes
operate on the cliff face to
weaken it and provide
material for coastal erosion.
What is weathering?
Biological weathering
What has caused the cracks to appear?
Chemical weathering
How do you think these rocks have become weathered?
Can you explain…
Colin forgot to chill the wine so he put
it in the freezer to quickly make it cold
– but then forgot it was there!
Next time he went to the freezer he
found it totally shattered.
Explain what has happened.
The water expanded as it
froze, creating huge forces.
These shattered the glass
bottle.
What are the different types of
weathering?
Mechanical weathering
Frost shattering
• Daily
temperatures
fluctuate around
0oC
• Ice occupies 9%
more volume
• Freeze-thaw
process widens
joints
Mechanical weathering
Exfoliation
• Outer layers of
rock warm faster
and cool more
rapidly
• Outer layers peel
like an onion
(onion skin
weathering)
Mechanical weathering
Pressure release
• Rocks developed under great pressure.
• Later exposure releases pressure and
exposure to atmosphere.
• Cracks develop and sheeting occurs
Mechanical weathering
Salt crystallisation
• Slightly saline water
enters pore spaces
• Evaporation leaves
salt crystals which
exert stresses on the
rock
• This leads to granular
disintegration
Biological Weathering
Biological
weathering
• Plant / tree roots
expand along
joints and
bedding planes
• Blocks of rock
become
detached
Chemical weathering
Oxidation
• Rocks exposed to
oxygen causes rocks
to crumble
• E.g. Iron in a ferrous
state is changed by
oxygen in to a ferric
state.
• Rocks change colour
from a blue grey to a
reddish brown
Chemical weathering
•
•
•
•
Hydration
Rocks capable of absorbing
water
E.g. water added to anhydrite,
gypsum results
Active following periods of wet
and dry weather
Also classed as a
physiochemical process – that
is, they swell and exert
pressure as well as change
chemical structure
Chemical weathering
Hydrolysis
• Hydrogen in water reacts with minerals
• E.g. Breakdown of feldspar (mineral in
igneous rock) to granite
Chemical weathering
Carbonation
• Rainwater contains
carbon dioxide, which
produces carbonic
acid.
• Dissolves limestone in
to solution (calcium
bicarbonate (soluble)).
Chemical weathering
Solution
• Minerals which
are soluble
dissolve, with
increasing acidity
in the water
Chemical weathering
Acid rain
• Human activity increasing carbon dioxide,
sulphur dioxide and nitrogen oxide
• Increases rate of carbonation of limestone
What is mass movement?
What are the different types of
mass movement?
Click for clip