Weathering. Miss Johnstone’s Expectations Arriving and leaving the classroom Presentation ...
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Transcript of Weathering. Miss Johnstone’s Expectations Arriving and leaving the classroom Presentation ...
Weathering
Miss Johnstone’s Expectations
Arriving and leaving the classroom
Presentation
Underline your titles
Always put the date
Draw in pencil
Draw a line under previous lessons work and carry on
Learning Objectives
To be able to define weathering.
To be able to identify the three different
types of weathering.
To be able to explain the three types of
weathering.
What is Weathering?
Weathering is the breakdown of rocks by
three different processes – biological,
chemical and physical. Weathering takes
place where the rock is – no movement
is involved.
Weathering
Chemical
Limestone, Chalk or Marble
Biological
Plants and Animals
Physical
Onion Skin(Exfoliation)
Freeze-Thaw
Chemical Weathering(Order the statements)
Limestone, chalk or marble is dissolved or weakened.
The rocks are worn away or broken up.
Carbon dioxide mixes with rainwater to create a weak acid.
The weak acidic rain attacks the rocks.
Chemical Weathering(Order the statements)
3. Limestone, chalk or marble is dissolved or weakened.
4. The rocks are worn away or broken up.
1. Carbon dioxide mixes with rainwater to create a weak acid.
2. The weak acidic rain attacks the rocks.
Biological Weathering - Animals
Biological Weathering(Order the Statements)
Animals dig under the rocks.
Rocks collapse or fall apart.
Rocks are undercut and cracks are widened.
Plants grow into cracks in the rocks.
Rocks loosened and broken up.
Biological Weathering(Order the Statements)
2. Animals dig under the rocks.
5. Rocks collapse or fall apart.
3. Rocks are undercut and cracks are widened.
1. Plants grow into cracks in the rocks.
4. Rocks loosened and broken up.
Onion Skin Weathering (Exfoliation)
• Onion-skin weathering is
also known as exfoliation.
• During the day the
temperature rises
• The outer layers of the rock
heat up and expand
• This cycle continues to
widen the cracks in the
outer layer.
• Eventually, the outer layers
‘peel’ off like an onion.
• The pealed layers remain
where they fall.
• During the night the
temperatures fall.
• The expanded layers of the
rock cool down and
contract.
• Cracks form in the outer
layers of the rock.
Freeze-Thaw Weathering
• Cracks in the rocks get wet and filled with water.
• At night the temperature drops below 0oC.
• The water in the cracks freezes.
• As the water freezes, it expands.
• The cracks become wider.
• The temperature rises above 0oC.
• The ice thaws and contracts.
• This cycle continues widening and enlarging the cracks.
• This continuous process causes rocks to be broken up
For both chemical and physical weathering
(You can leave biological)
1. At what temperature and rainfall levels does the strongest chemical or
physical weathering occur?
2. Suggest a country where this might be, i.e. the Sahara
Desert will have very strong onion skin weathering.
Due: Tuesday 3rd February