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Weathering
Tropical areas have more vegetation growth and so more weathering.

Weathering

One topic looked at in GCSE Geography is weathering. This is the natural process which causes the breakdown of rocks and minerals by chemical, biological or physical agents and is not to be confused with erosion. Erosion is the process in which material is moved whereas weathering occurs in situ.

Weathering is the breakdown of rocks, soil and naturally occurring minerals, as well as all the artificial minerals that have been made by human activity, such as bricks and concrete. Weathering is the process that eventually turns mountains into grains of sand on a beach.

Various factors influence the rate of weathering, including:

1 .
Weathering is normally studied as the first stage in a two stage process - weathering and erosion. What is the key difference between weathering and erosion?
Weathering is in situ (in one place), whilst erosion involves moving material away
Weathering is destructive, whilst erosion forms structures
Erosion is the removal of material, whilst weathering is the placing of material
Weathering is only caused by climate (e.g. rain and ice), whilst erosion is caused by all other destructive forces
When rock has been weakened and broken up by weathering, erosion can then occur. Erosion happens when material is moved to another place by water, gravity, ice or wind
2 .
What are the three types of weathering?
Mechanical, physical, stress
Biological, stress, macro
Chemical, biological, physical
Macro, micro, massive
The three types of weathering are broadly grouped into chemical, biological (also called organic) and physical (also called mechanical)
3 .
In temperate regions freeze-thaw weathering, also known as frost shattering, is a major source of weathering. What are the conditions required for freeze-thaw weathering to occur?
Temperatures below freezing allowing ice to form
Day time temperatures hot enough to crack rocks and night time temperatures cold enough to shrink rocks and so widen these cracks
Large amounts of water that can seep into rocks and be available to freeze
High diurnal (daily) temperate range, with night time temperatures below freezing point, and day time temperatures consistently above freezing. Water available to freeze in cracks in the rocks
This is a great question if you get it in the exam. The clue is in the name - freezing and thawing needs temperatures low enough to freeze and high enough to thaw the ice back to water
4 .
How does freeze-thaw weathering occur?
Ice forms and builds up night after night. As the ice builds up on the face of the ice block it forces the rocks apart
Cracks in rock fill with water. When the temperature falls ice forms and expands, widening the crack. When the temperature rises the ice melts and water seeps deeper into cracks to repeat the cycle
The rocks themselves freeze during the night and thaw during the day. This eventually cracks the rocks
Freezing rivers push back on their banks and expand the width of the river
Think of the things freeze-thaw weathering requires: diurnal temperature range, available water and cracks in the rocks. This is so the water can fill the cracks and, as ice forms, expand
5 .
Areas such as Scotland have large amounts of freeze-thaw weathering but why doesn’t freeze-thaw weathering occur in very cold locations such as the Polar regions?
The temperature range rarely comes above freezing meaning that there is no water available to seep deeper into the rocks to further expand the crack
There is no night and day cycle so there isn’t a temperature range
The water is salt water which can’t freeze
The rock types are too tough to be weathered by this method
The polar regions are also known as the polar deserts. They are so cold that all the fresh water and a huge amount of the salt water is tied up as ice and never thaws. This means that there is no liquid water to allow freeze-thaw weathering
6 .
Which of the following is not an example of physical weathering?
Hydration
Freeze-thaw weathering
Exfoliation
Salt crystal growth
Hydration is a chemical process where certain rocks absorb water into their structure. It is a type of chemical weathering
7 .
Which of the following types of weathering has the correct label attached?
The sun heating rocks and causing them to expand and crack - chemical weathering
Tree roots forcing their way into cracks in rocks and forcing them wider - biological weathering
Acid rain dissolving limestone rocks - physical weathering
Waves breaking down cobbles into sand - biological weathering
Biological weathering is sometimes classified as a type of physical weathering, but anything done by living things can be classified as biological weathering
8 .
Rocks containing iron often show a red colouration. This is a type of chemical weathering. What is occurring to make the rocks turn red?
Iron compounds within the rock structure are oxidising in the same way ferrous metals rust
The red colouration was naturally there and the weathering exposes the colour
The rock is taking up the red colour from the soil and these are exposed by chemical weathering
Copper compounds in the rocks are oxidised to form this red colour
Iron is one of the major elements found in many types of rock
9 .
Which of the following is not a reason for tropical areas having higher rates of weathering than temperate zones?
A large amount of rainfall leads to increased weathering
Large amounts of vegetation lead to increased biological weathering
Great forces of wave action on the coastal zone lead to increased weathering
Being closer to the equator there are higher temperatures leading to higher rates of chemical weathering
In tropical areas, higher levels of rainfall, warmer conditions and better light all lead to a higher rate of vegetation growth which in turn leads to increased weathering. The rainfall and heat also cause weathering themselves
10 .
When rocks are heated and expand, and then cool and contract, thin slivers of rock tend to flake off at the surface. What is the name given to this weathering process?
Freeze-thaw weathering
Erosion
Pavementing
Exfoliation
Exfoliation is the process in which the top layer of rocks is gradually removed via expansion and contraction caused by temperature differences
Author:  Ruth M

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