1.1.5- Processes of coastal weathering, mass movement, erosion and characteristics and formation of associated landforms and landscapes Flashcards
What is weathering?
`Weathering is the in-situ breakdown of
rocks by chemical, mechanical or
biological agents. It does not involve any
movement
what is sub ariel process ?
The coast is the narrow zone
between the land and the sea.
the landscape will be influenced by
processes on the land as well as
the sea.
Sub-aerial processes include weathering and mass movement.including landslides, slumps and rainfall - rain
These processes operate on the cliff face to weaken it and provide material for coastal erosion.
what is mechanical weathering and give some examples ?
Mechanical weathering breaks down rocks due to the exertion of a physical force, it does not involve a chemical change
Freeze-thaw - Water expands by 9% in volume when freezing, exerting a force within cracks and fissures; repeated cycles force cracks open and loosen cracks
Salt crystallisation - The growth of salt crystals in cracks and pore spaces can exert a breaking force, although less than for freeze-thaw
What is chemical weathering?
What are the three types of chemical weathering?
Chemical weathering involves a chemical reaction and the generation of new chemical compounds
Carbonation - The slow dissolution of limestone due to rainfall of pH level 5.6
Oxidation - The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume contributing to mechanical breakdown
Solution - The dissolving of rock minerals, such as rock salt
What is biological weathering?
What are the two types of biological weathering?
Biological weathering often speeds up mechanical or
chemical weathering through the action of plants, bacteria or animals
Plant roots - Trees and plant roots growing in cracks and fissures forcing rocks apart
Rock boring - Many species of clams bore into rock and may also secrete chemicals that dissolve rocks
Define what mass movement means
Mass movement is the down slope movement of earth materials under the influence of gravity
Mass movement can be classified into 4 main
types – flow, slide, fall and creep. Each
process represents a flow or transfer of
material and can be considered to be an
output from one store (land) and an input to
another store (beach/sea). The type of
movement at any one place depends upon a
range of factors – angle of the slope or cliff,;
rock type and structure; vegetation cover; how
wet the ground is
what happened in 1993 in north yorkshire ?
In 1993, 60m of cliff slumped
onto the beach near Scarborough in North
Yorkshire, taking with it part of Holbeck
Hall Hotel. The hotel had to be demolished.
What are the 6 types of mass movements?
Rockfall: fragments of rock break away from
the cliff face, often due to freeze-thaw weathering
Mudflow: Saturated soil and weak rock flows down a slope
Landslide: Blocks of rock slide downhill
Rotational slip: Slump of saturated soil and weak rock along a curved surface
Soil creep: The extremely slow downslope movement of the loose material such as soil above the bedrock
Which is the nature of movement for each of the
mass movements?
How fast is the movement for each of the mass
movements?
Soil creep Imperceptible
Solifluction Creep/flow (extremely slow) Wet
Mudflow Flow quite rapid Wet
Landslide
Rotation Slip Slide Usually rapid Wet/Dry
Rockfall Fall rapid Dry
What is rock toppling?
Blocks or even columns of rock, weakened by
weathering, fall seawards.
where has rock toppling occured ?
This has occurred in the columnar basalt of the Giants Causeway in Northern Ireland
what is hydraulic, abrasion, attrition and corrosion action ?
hydraulic action is the erosion caused by the force of water
abrasion - is the erosion caused by water carrying the rocks and throws them on the cliff
atrrition - erosion caused by small rocks on rock smashing against each other making themselves smaller
corrosion - erosion caused the chemical processes which allows the rock to dissolve
what are the 6 factors that affect coastal erosion ?
- WAVES
- ROCK TYPE (LITHOLOGY)
- PRESENCE OR ABSENCE OF BEACH
- SUBAERIAL PROCESSES
- COASTAL MANAGEMENT
How do cliffs retreat backwards?
Waves break against the
base of a cliff
The base of the cliff is
undercutted
The overhang eventually
collapses due to no support
A steep sided cliff is left
behind
The process repeats itself
resulting in the retreat of the
cliff
What factors help a cliff to retreat backwards?
Weathering and mass movement
Rocks prone to weathering and mass movement will be subject to severe erosion
Rock type
Weak rocks result in rapid retreat
e.g. till at the Holderness coast 1-10m/year
e.g. granite in Cornwall 1mm/year
Wave energy
High energy waves, driven by strong
prevailing winds and a long fetch will
increase the rate of retreat
