Sub Arial Processes - Weathering Flashcards
What is weathering (2)
The breakdown or disintegration of rock in situ at or close to the ground
Leads to the transfer/flow of material
Type of weathering (3)
Mechanical
Chemical
Biological
Mechanical weathering (2)
Freeze thaw
Wetting and dry
Freeze thaw weathering (4+)
Water enters cracks in rocks
Temp drops below 0oC = feeezes + water expands by almost 10%
Ice occupies more space and so exerts pressure on the surrounding rock
Repeats = rock break aways and collect at the base of the cliff as scree
Wetting and drying (4+)
Affect rocks rich in clay
Clay expands when wet and contracts and cracks when dry
Over time = the rocks break up
The cracks = allow water to seep into cliff = susceptible to other processes = mass movement
What is mechanical weathering
Break up of rock without chemical chnage
What is biological weathering
Break up of rock by organic activity
Biological weathering - roots (2)
Plants grow on cliff tops and roots grow into s all cracks
These cracks widen as roots grow = break up the rock
Biological weathering - birds and animals (2+)
Cliff nesting birds dig burrows into the cliff
Puffins + rabbits + piddock
What is chemical weathering (2)
Breakdown of rocks by changing the composition
Involves dissolving due to chemical reaction
Types of chemical weathering (2)
Oxidation
Carbonation
What is carbonation (2++)
Rain absorbs CO2 from atmosphere = slightly acidic carbonic acid
Reacts with calcium carbonate in rocks such as chalk or limestone = calcium bicarbonate
Rocks dissolve overtime
What is oxidation (3+)
Occurs when oxygen react with iron in rocks
Forms iron oxide = red powder
Iron oxide is weak = rocks more vulnerable to weathering
Positive feedback - weathering (4)
Weathering occurs
Rate of debris removal exceeds rate of weathering
Cliff faced exposed
Weathering increases
Negative feedback - weathering (4+)
Weathering occurs
Rate of debris removal slower than rate of weathering
Build up of debris reduces Cliff exposure
Weathering rate decreases
