Sub aerial processes Flashcards
What are sub aerial processes?
Weathering and mass movement
What is weathering?
The breaking down of rock and it can be divided into mechanical, chemical and biological weathering
What is biological weathering caused by?
Roots of vegetation and nesting birds
What is mechanical weathering?
Physical processes like freeze thaw weathering and salt crystalisation
When does salt crystalisation occur?
It occurs between cracks in rocks and overtime the salt applies pressure on the cracks
What happens in freeze thaw weathering?
Breaks up rock as water freezes in cracks as the ice applies pressure and breaks the rock
Why does chemical weathering occur?
As a result of a weak chemical reaction between water and rock
What rocks does chemical weathering occur with?
Limestone
What does carbonic acid react with during chemical weathering?
Carbonic acid (formed by rainwater and carbon dioxide) reacts with calcium carbonate in limestone to form calcium bicarbonate
Why does limestone get weathered?
Because calcium bicarbonate is soluable in water, this leads to complex cave systems in coastal zones
What does weathering weaken?
Cliffs which speeds up the rate of erosion
What is mass movement?
The movement of material downslope under the influence of gravity
What rapid events can mass movement lead to?
Landslides and rockfalls
What is a common type of mass movement along coasts?
Rotational slumps
What do marine processes do to cliffs?
Marine processes erode and undermine the base of the cliff
What infiltrates into the slope through unconsolidated porous material?
Rainfall
What does rainfall infiltrating through unconsolidated porous material create?
A slip plane as it reaches an impermeable material such as clay
The clay and accumulating water enables…
The weighted saturated material above to slump
Whta makes the White Cliffs of Dover susceptible to mass movement?
They are made of chalk cliffs and weather allow for wetting and drying cycles. This internal stress makes the cliff weaker making sloping more likely.
What led to a large slumping event in Dorset?
The porous sandstone absorbed rainfall making the cliff heavier and making mass movement more likely
