Systems And Processes In Coasal Environments Flashcards
Define erosion
The wearing away of surface by the mechanical action of glaciers, rivers, wind and waves
Define fetch
The distance of open water a wind blows uninterrupted which helps determine the size and energy of waves reaching the coast
Define mass movement
The movement of material downhill under the influence of gravity and assisted by rainfall
Define weathering
The breakdown or decay of rock that remains in situ until later moved by an erosion all process
What are the 4 main sources of energy in coasts
Wind, waves, tides and currents
When wind speeds are high and uninterrupted…
Waves are stronger
What type of wind encourages longshore drift
Prevailing wind direction
One type of wind erosion
Abrasion
3 characteristics of waves
Height, length and frequency
Constructive waves
Low wave heights
Long wavelength
Low frequency
Strong awash
Weak backwash
Destructive waves
High wave hieght
Short wavelength
High frequency
Strong backwash
Weak swash
Wave refraction
As waves approach coast the become more parallel
It drags the shallow water to th e headland
Increases wave speed and height
concentrate on headlands causing greater erosion
Longshoreman currents
Approach coast at an angle moving water along surf zone and transporting sediment
Rip currents
Strong currents moving away from shoreline - extremely hazardous
Upwelling
Movement of cold water to the surface replacing warm water creating nutrient rich cold oceans
What are tides
The period rise and fall of the level of the sea n response to the gravitational pull of the sun and the moon
How are spring tides formed
When the moon and sun are in line
The tide rising force is strongest
How are neap tides formed
When the moon and sun are perpendicular (90°)
Lowest tidal range
10-30% lower than average
What do tidal ranges determine
The upper and lower limits of erosion and deposition
The amount of time the littoral zone is exposed to sub aerial weathering
What are storm surges
When meteorological conditions give rise to strong winds producing higher water levels
What cause low pressure conditions in the North Sea
Depressions
Coastal sediment budget
The balance between the sediment being input and output of the coastal system
Low energy coast features
Wave energy is low
Deposition > erosion
Beaches and spits
High energy coasts features
Strong wave energy
Erosion > deposition
Headlands, cliffs, wave cut platforms
Sources of coastal sediment
Cliffs
Estuaries
Offshore sand banks
Sediment cells
Areas of coastline separated from others by well defined boundaries
5 marine erosion processes
Hydraulic action
Wave quarrying
Abrasion
Attrition
Solution
Explain hydraulic action
Impact on rocks from sheer force of water
Exerts pressure on rock surface
Weakens and cracks or breaks down
Explain wave quarrying
A breaking wave traps air into cliff face and is compressed
Creates pressure
Water pulls back and there is an explosive effect
This weakens the cliff and it breaks down
Explain abrasion
Material the sea picks up wears away at rocks
Explain solution
Dissolving of calcium based rocks
Sea water between 7.5-8.5 pH and so is alkaline
Howeve racid rain may break down rocks
What is the rate of erosion effected by
Wave steepness
Fetch
Sea depth
Coastal configuration
Human activity
Concordat coastline
Rocks running parallel to the coastline, protect the coast from erosion
Discondcordant coastline
Rocks running at right angles to coastline
Processes of marine transportation
Traction
Saltation
Suspension
Solutiom
Explain traction
Large stones and boulders rolling on the seabed by moving seawater
Explain saltation
Small stones bounce on the seabed
High energy conditions
Explain suspension
Small particles of sand and silt are carried along by moving water
Carried and more is picked up by the turbulence
Aeolian deposition
Transportation and deposition of sediment by the wind e.g surface creep
3 types of sub aerial processes
Mechanical
Biological
Chemical
Explain freeze thaw
Water enters cracks of rock and freezes and expands
By 10%
Exerts pressure on the rock
Cracks widens as process repeats
Biological weathering
Breakdown of rock by the actions of vegetation and organisms e.g algae secrete chemicals promoting solution
Explain oxidisation
Rocks disntiegrate when oxygen reacts with minerals
Forms oxides and hydroxides
Explain hydration
Physical addition of water to minerals
Causes rock to expand and disintegrate
Weakens rock and joints allowing further chemical weathering
Explain hydrolysis
Mildly acidic water reacts to rock minerals
Creates clays and dissolvable salts
Disintegrates in the rock and makes it weaker
Susceptible to further degradation
Explain carbonation
CO2 dissolved in rainwater makes carbonic acid
H2CO3 reactions with calcium rock to create calcium dissolved easily
Also presence of sulphur oxide and nitric acid creates acid rain
Mass movement is dependent on
Level of cohesion with the sediment
Height of the slope
Grain size of the sediment
Level of saturation
Types of mass movement
Landslides
Rock falls
Mudflows
Rotational slip or slump
Soil creep
