Paper 1) Coastal Environments Flashcards
The coast as a system
The coast is a natural system which means that it is a physical cycle where stores and flows of material and energy are linked together.
Erosion definition
The wearing away of rocks to the sea
How coastal erosions impact the UK
-28% of the UK coastline is eroding at varying speeds
-east - more erosion as rocks are softer
-highest rates up to 3.5 meters a year
Types of erosion processes
-hydraulic action
-corrasion/ abrasien
-solution
-attrition
Hydraulic process
-water is forced into cracks into rock
-air compresses
-wave retreats, compressed air blasts out
-damages rock
Corrasion/ abrasien
-rocks are thrown at the cliff
-when waves are destructive they have enough power to throw materials carried to cliff face
-acts like sandpaper, waves cliff away
Solution (erosion process)
-the sea contains salt. Material broken from cliff are dissolved by salt water in waves
-waves crash at cliff, salt and acids cause the rocks to erode
Attrition
-pieces of rock and pebbles from cliff are thrown around, hit each other
-becomes smooth, round
Swash vs backwash
-Waves towards coast
-waves moving away from coast
Constructive wave characteristics
-low energy
-strong swash
-weak backwash
-low wave height
-wide and flat beach shape
-low frequency (6-8 waves per minute)
Destructive wave characteristics
-high energy
-weak swash
-strong backwash
-high wave height
-steep and narrow beach shape
-high frequency (10-14 waves per minute)
Factors affecting coastal erosion
-rock type
-rock structure
-type of coastline
-type of wave
Factors affecting coastal erosion - rock type
Easily eroded (clay and shale):
-wide beaches
Resistant (limestone and chalk):
-steep cliffs, headlands
Factors affecting coastal erosion - rock structure
-rocks parallel to coastline - concordant
-rocks outcrop at right angles to the coast - discordant
Factors affecting coastal erosion - shape of coastline
-headlands are exposed to full force of the sea
-headlands can protect surrounding bays which can be sheltered from erosion
Factors affecting coastal erosion - type of wave
-Destructive wave
-Constructive wave
Types of transportation processes
-traction
-saltation
-suspension
-solution
Traction
Pebbles, large materials roll along the sea bed
Saltation
Small pieces (shingle, large sand grains) bounced along the sea bed
Suspension
Small particles (silts, clays) suspended in the flow of the water
Solution - transportation process
Minerals in rock (chalk, limestone) dissolved in sea water, not visible
Longshore drift
- The prevailing wind pushes waves up the beach at an 45 angle, picking up beach material in the swash
- As the wave retreats, the backwash drags this material back down the beach at a right angle
- Another wave picks up the material and moves it up the beach again, in the swash
- The backwash moves the material back down the beach
- The process continues and the material is moved along the coastline in a zig-zag motion until it meets a barrier (such as a headland or a groyne) and is deposited
Sediment cell
Sediment moved along the coast by longshore drift appears to form part of a circular cell which leads to it eventually returning updrift.
Dredging of offshore shingle banks can therefore contribute to beach depletion.
Coastal deposition
When material being transported dropped by constructive waves as waves have less energy