Weathering Processes
This PPS will explain:
• Secondary landforms – created by
• Erosion – Transportation and Deposition
• 3 types of WEATHERING:
• Mechanical (Physical) processes
• Chemical processes
• Organic processes
Your task
• As you watch this PPS you need to
record information in your books or
on a word document.
• Later on you will be given a task
that requires you to find your own
examples of these processes.
What do the following photos have in common?
The photos all show weathering
processes
• Secondary landscapes are formed through
weathering processes.
• These processes act continually upon the
landscape.
• They slowly change the shape and
appearance of the landscape.
• The three processes are weathering,
erosion and mass movement.
Weathering
• Is the breakdown of
rock in the place it
was found, by the
action of weather
chemicals, gravity
(glaciers), plants and
animals.
Erosion
Rivers, waves, ice and wind
transport rocks, rock fragments
and soil away and deposit them
somewhere else.
Mass Movement
When rocks,
loosened by
weathering move
downhill under
the influence of
gravity.
Transportation
Is the movement of
materials by
weathering
processes:
Wind, rain, running
water, wave action
and gravity.
Deposition/
aggradation Is the deposition of
material, which can
lower relief in
differences of high
and low points in a
landscape.
Streams, glaciers,
wind, and waves
also deposit
materials.
Mechanical
Weathering
Frost action is a type
of weathering where
water actually seeps
into cracks in the
rock. The water
freezes as the
temperature drops.
As water freezes it
expands.
Geography4kids website
This expansion creates
a wedge inside the rock,
encouraging is to crack
and split apart. This
picture shows one of
those fractures.
Mechanical
Weathering
Salt wedging. As water
enters the holes and
cracks in the surface of
rocks, it often carries salt
with it. As the water later
evaporates, the salt is
left behind. After a while,
salt crystals grow and
create wedges that force
the rock apart.
Mechanical
Weathering
Glaciers are extremely effective weathering
and erosional agents. A glacier is capable of
carving deep valleys into bedrock as well as
scraping all loose material (soil and weathered
bedrock) off from a landscape.
Click on the link below to view a Youtube clip of Mass movement and
gravity in action.
https://youtube.googleapis.com/v/zt8qoggxWVg
Erosion – Mass
Movement
Talus Cone, Lake Louise,
Canada.
Talus cones are rock
falls, which are driven
by gravity, it is one of
the main ways by
which cliffs erode.
As fractures in the bedrock grow, large blocks of
rock can break off and accumulate below. If rock
fall is concentrated anywhere, then a coneshaped deposit will form.
Chemical Erosion
Chemical solutions act to break down rock,
such as when calcium carbonate is subjected
to humid conditions and dissolves to form
limestone. Chillagoe caves
Click on the link below to view a Youtube clip of chemical and mechanical
weathering processes
https://youtube.googleapis.com/v/P8oWj3PVK9E?start=155&end=339&autoplay=
1&loop=1
Karst
Is an example of a
landscape formed
mainly by a chemical
process - rock being
dissolved by surface
or groundwater.
2 key ingredients:
Rock (typically
limestone) + Water
LIMESTONE QUARRY
Which process is shown in this
photo?
Weathering – rain and wind
Which process is shown in this photo?
Weathering – wave, salt wedging, mass
movement
Erosion - transportation
Which process is shown in this photo?
Weathering – Gravity, Mass movement, Talus
cones
Which type of weathering is most likely to…
• Occur in a tropical climate?
•
Chemical, mechanical weathering and
erosion
• Happen in Cairns more in the summer than
winter?
Mechanical weathering and erosion
• Happen fastest in a tropical rainforest?
– Chemical (moss and lichen) and
mechanical weathering (tree roots cracking
rocks)