Processes Flashcards
Geomorphic processes
The physical and chemical interactions between the earths surface and the natural forces acting upon it to produce landforms.
Mass movement processes
- Refers to the movement of material down a slope.
- they are sub-aerial (above ground)
Dependent on:
- slope angle
-particle size
-temperature
-saturation
LANDSLIDES ~ cliffs made of softer rocks slip when lubricated by rainfall.
ROCKFALL ~ rocks undercut by the sea or slopes , affected by physical weathering processes.
MUDFLOWS ~ heavy rain causes fine material to move downhill.
ROTATIONAL SLIP / SLUMPING ~ where soft material overlies resistant material and excessive lubrication takes place.
SOIL CREEP ~ very slow movement of soil particles down slope.
Weathering
- a significant process in the formation of coastal landscapes.
Three types :
-physical/mechanical
-chemical
-biological
physical / mechanical weathering
- causes the break down of rock
-no chemical alterations occur - process increases the exposed surface area of the rock, allowing further weathering to take place.
four types:
- freeze thaw
- pressure release
- thermal expansion
- salt crystallisation
Pressure release
Occurs when rocks expand and fracture parallel to the surface as the pressure is released.
Parallel fractures ~ pseudo- bedding planes.
GRANITE ~ important in the exposure of sub-surface rock. also known as DILATION,
freeze thaw
Occurs when water seeps into cracks in rocks , freezes and expands (by 9-10%) , breaking the rocks apart.
Thermal expansion
- rocks expand when heated
- rocks contract when cooled
- frequent cycles of temperature change can lead to the outer layer of rock cracking or flaking off.
Salt crystallisation
Crystals are formed in pore spaces in porous rocks creating stress which causes rocks to disintegrate.
This is caused by:
- solutions of salt seeping into pore spaces in porous rocks
- salt precipitate, forming crystals
Examples:
- sodium sulphate
- sodium carbonate
These expand by 300% in changing temperature around 26-28 degrees Celsius.
Chemical weathering
- causes the decay of rock
- involves chemical reactions between moisture and minerals within the rock
- can reduce the rocks chemical constituents or alter its chemical and mineral composition.
5 types:
-oxidation
- carbonation
- solution
- hydrolysis
- hydration
oxidation
the reaction with OXYGEN either in the air or in water.
IRON:
- susceptible to this process
-becomes soluble under acidic conditions and the original structure is destroyed
Carbonation
- Rainwater combines with dissolved carbon dioxide int he atmosphere to produce CARBONIC ACID.
- CALCIUM CARBONATE ~ reacts with carbonic acid to produce calcium bicarbonate, which is soluble.
- this process is REVERSIBLE.
Solution
- any process by which a mineral dissolves in water.
-some salts are soluble in water
- other minerals such as iron are only soluble in very acidic conditions (PH 3).
Hydrolysis
A chemical reaction between rock minerals and water.
Examples:
SILICATES ~ combine with water , producing secondary minerals such as clays.
FELDSPAR ~ reacts with hydrogen in water , producing KAOLIN (China clay)
Biological weathering
The result of pant and animal activity.
Two types:
- tree roots
- organic acids
Hydration
Water molecules are added to rock minerals creating new mineral of a larger volume .
- causes surface flaking a some minerals expand by 0.5% as they absorb water.
