2.a. Coastal landforms are inter-related and together make up characteristic landscapes. Flashcards
What are geomorphic processes?
Processes that shape coastal landforms.
What are the 5 geomorphic processes? Which shape erosion/ depositional landforms?
Weathering. (Shape erosion landforms).
Mass Movement. (Shape erosion landforms).
Wave Processes. (Shape erosion landforms).
Aeolian Processes. (Shape deposition landforms).
Fluvial Processes. (Shape deposition landforms).
What is weathering?
(Weathering)
A process which uses energy (mostly thermal) to produce physically, chemically or biologically altered materials from surface or near surface rock.
What are the types of weathering?
Physical/ mechanical, biological, and chemical.
Physical weathering is the largest contributor to what?
(Physical/ Mechanical Weathering)
Rock breakdown.
How does physical weathering erode rock?
(Physical/ Mechanical Weathering)
By increasing the surface area exposed.
This allows other weathering processes to occur.
What can render physical weathering less effective?
(Physical/ Mechanical Weathering)
Low air temperatures.
When water enters a rock crack and freezes, how much does it expand by?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
Nearly 10%.
What is freeze thaw weathering?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
The process by which the expansion of water in a rock (confined spaces) exerts pressure, causing it to split and break off.
Does freeze-thaw weathering work only on weak rocks?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
No, the process even works on resistant rocks.
Outline the process of salt crystallisation.
(Salt crystallisation)
(Physical/ Mechanical Weathering)
Solutions of salt seep into porous rock.
The salts then precipitate forming crystals.
This eventually dissolves the rock from stress.
Give an example of a salt solution. By how much does this expand by when in temperatures of around 26-28°C?
(Salt crystallisation)
(Physical/ Mechanical Weathering)
Sodium sulphate, sodium carbonate.
Roughly 300%.
What is chemical weathering?
(Chemical weathering)
The decay of rock which involves chemical reactions between moisture and some minerals within the rock.
It can: reduce stability, reduce the rock to chemical constituents and later chemical composition.
What can chemical weathering do to a rock?
(Chemical weathering)
Reduce stability.
Reduce the rock to chemical constituents and later, chemical composition.
Outline the process of carbonation.
(Carbonation)
(Chemical weathering)
Rainwater combines with dissolved CO2 from the atmosphere to produce a weak carbonic acid.
This reacts with calcium carbonate in rocks, e.g. limestone, to produce calcium bicarbonate (soluble).
Is carbonation reversible?
(Carbonation)
(Chemical weathering)
Yes.
The precipitation of calcite happens during what? What does this form?
(Carbonation)
(Chemical weathering)
Evaporation of calcium rich water in caves.
This forms stalagmites and stalactites.
What is oxidation?
(Oxidation)
(Chemical weathering)
The process that causes minerals in rocks to react with oxygen, either in the air or water.
What element is especially susceptible to oxidation? Why?
(Oxidation)
(Chemical weathering)
Iron.
This is because it becomes very soluble under extreme acidic conditions, in turn destroying its original structures.
Oxidation often attacks what combination of rock.
(Oxidation)
(Chemical weathering)
Iron-rich cements that bind sand grit together in limestone.
What happens to some salts when in water?
(Solution)
(Chemical weathering)
They become soluble.
Some salts become soluble in water. Give an example of a salt that does not do this. How does it affected instead?
(Solution)
(Chemical weathering)
Iron.
It is only affected by very acidic waters (around pH 3).
What is solution?
(Solution)
(Chemical weathering)
Any process by which a material dissolves in water.
(However, mineral specific processes such as carbonation can be separately identified).
State Van’t Hoff’s law.
(Chemical weathering)
A 10°C change leads to a x2.5 increased rate of chemical reactions, (up to 600°C).
How do tree roots cause stress in rocks?
(Tree roots)
(Biological weathering)
Grow into cracks and joints exerting pressure outwards.
How does the falling of trees weather rocks?
(Tree roots)
(Biological weathering)
Their roots can exert leverage on rock and soil.
This exposes them on the surface to furthering weathering processes.
Other than falling trees exposing rocks and soils, what else can do this?
(Tree roots)
(Biological weathering)
Burrowing animals.
Tree roots can have a significant effect when they are where?
(Tree roots)
(Biological weathering)
On cliff tops and cliff faces.
When are organic acids produced?
(Organic acids)
(Biological weathering)
During the decomposition of plant and animal litter.
Organic acids are created from the decomposition of litter, but how does this contribute to weathering?
(Organic acids)
(Biological weathering)
Causes soil water to become more acidic.
This then reacts with some minerals (chelation).
What is chelation?
(Organic acids)
(Biological weathering)
Where organisms produce organic substances that have the ability to decompose minerals and rocks by the removal of metallic cations.
How can blue-green algae produce a weathering effect?
(Organic acids)
(Biological weathering)
By producing a shiny film or iron and manganese oxides onto rocks.
Outline how biological weathering may occur on onshore platforms.
(Organic acids)
(Biological weathering)
Through molluscs.
These may secrete acids which produce small surface hollows in the rock.
What is mass movement?
(Mass movement)
The process by which forces act on a slope where gravity exceeds friction.
Where is mass movement most significant?
(Mass movement)
Cliffs.
When mass movement occurs on cliffs, what happens to sediment?
(Mass movement)
Rock and regolith fall and are added to the sediment budget.
Rock-falls occur on a cliff of what angle?
(Rock-falls)
(Mass movement)
40° or more.
Rock-falls are primarily influenced by what weathering type? How?
(Rock-falls)
(Mass movement)
Physical weathering.
This is done through the exploiting of joints and exposed bedding planes.
How do wave process contribute to the mass movement process?
(Rock-falls)
(Mass movement)
They erode the moved material, e.g. fallen from cliffs.
When do slides often occur?
(Slides)
(Mass movement)
Often common when waves undercut the cliff base.
Slides often move in what way? What do they move along?
(Slides)
(Mass movement)
In a linear motion.
They move along a fault or bedding plane.
Rotational slides are also called what?
(Slides)
(Mass movement)
Slumps.
When do slumps occur?
(Slides)
(Mass movement)
When there is movement along a curved slip plane.
Slumps are common in what rock type?
(Slides)
(Mass movement)
Weak rock types, e.g. clay.
Why do slumps occur in weak rock types?
(Slides)
(Mass movement)
This is because the rock becomes heavier as it gets increasingly more wet (gravity influence is stronger).
When sand is above a concealed weak rock type, why is it more likely to become wet?
(Slides)
(Mass movement)
Due to the open structure of the sand particles.
What is wave erosion?
(Erosion)
(Wave processes)
When breaking waves are able to erode the coastline.
