3.1.3.2 Systems and Processes Flashcards
What is the key part of the coastal system
Sediment
Why is the primary source of all energy the sun?
Because it heats the air, making low pressure areas
How is wave energy generated?
The air that is in high pressure areas (cold air) moves towards those of where low pressure (warm air) has risen. Thus creating win energy
How are currents created?
By the permanent or seasonal overeat of surface water in the seas and oceans due to its temperatures
Why is wind a vital input into the coastal system?
It is a primary source of energy for other processes
It is an important agent of erosie and transport
What are the features of wind as an input into the coastal system?
Long term prevailing wind direct
Fetch
Wave formation
A vehicle of abrasion - carries material that wears away landscape features
What are the charcteristics of a wave?
Height
wavelength/amplitude
Wave frequency
Why do waves slow down in shallow water?
Because friction in the seabed increases
What effect does the slowing down of a wave have on its characteristics?
Increases height and steepness until the upper part plunges forward and the wave ‘breaks’ onto the shore
What are the features of constructive waves?
Low wave height
Long wavelength
Powerful swash
Weak backwash
How are berms formed by constructive waves?
The weak backwash has insufficient force to pull sediment off the beach so material slowly but constantly is moved up the beach, forming the ridges
What are the characteristics of destructive waves?
High wave height
High frequency (10-14 a minute)
Short wavelength
Why do destructive waves have a strong backwash?
Because as they approach a beach, the rapidly steepen and plunge downwards when they break, therefore there is little forward movement of water
Why are most beaches subject to an alternating cycle kf constructive and destructive waves?
Because constructive waves build up the beach, causing it to be steeper
But destructive waves are associated with steep beach profiles, then destruct and reduce the beach profile
The pattern repeats itself
Why is dynamic equilibrium often impossible in the negative feedback cycle of waves and beach formation?
Be ause other factors like wind strength and direction are not constant
Why is the topography of the coastline important to determine the effects of wave action?
Because wave refraction around a coastline that is not a regular shape affects the energy of waves at different places
Why do headlands recieve concentrated wave energy?
Because water at the headland is deeper than that at the beach
Waves in deeper water do not lose speed as rapidly
So wave height is very high
Erosion is concentrated on the headland
What are longshore currents/littoral drift?
When waves approach the shore at an angle and swash and backwash then transport material along the coast in the direction of the prevailing wind and waves
What are rip currents?
Strong currents moving AWAY from the shoreline
Why do rip currents develop?
When seawater is piled up along the coastline by incoming waves
What is upwelling?
The movement of cold water from deep in the ocean towards the surface
The more dense cold water replaces the warmer surface water and creates nutrient rich cold ocean currents
They form part of the global ocean cirgulation currents.
What is a tide?
The periodic rise and dall of the level of sea in response to the gravitational pull ftom the sun and the moon
Why does the moon have greater influence on tides?
Because it is much nearer than the sun
How is a high tode created?
When the moos pulls water towards it and there is a compensatory bulge on the other side of the earth
What is the tide like in areas of the rest of world between the two bulges?
At its lowest
What do high tides follow?
The moon as it orbits the Earth
When is tide-raising force at its strongest?
Twice in a lunar month, when the moon, sun and Eart are in a straight line
What is spring tide?
When tides bulge at their highest (sun, moon and earth are in a straight line)
What are neap tides?
When the moon and sun are perpendicular to each other in relation to the Earth
High and low tides are between 10-30% lower than the average
What is tidal range?
The difference between height of sea water at high and low tide
Why are tidal ranges a significant factor in the development of a coastline?
Because they determine the upper and lower limits of erosion and deposition and the amount of time each day that the littoral zone open and exposed to sub aerial weathering
What is a tidal/storm surge?
When strong winds cause water levels to be much higher than those at high tide
Why does the North Sea and Britain experience storm surges?
Because depressions over the North Sea produce low pressure conditions that have the effect of raising sea levels
Strong winds drive waves ahead of the storm, pushing sea water towards the coastline
What is a high energy coastline?
A coastline where strog, steady prevailing wind creates high energy waves and the rate of erosion is greater than that of deposition
Example of high energy coastline
Cornwall (SW coast) Holderness Coast (NE coast)
What is a low energy coastline?
Where wave energy is low
The rate of deposition exceeds the rate of erosion of sediment
What landforms are Lund at low energy coastlines?
Beaches and spits
What landforms area found at high energy coastlines?
Headlands, cliffs and wave cut platforms
What are some sources of coastal sediment?
Streams/Rivers flowing nto the sea Estuaries Cliff erosion Off shore sand banks Material from biological origin (like fragments from marine organisms)
What is a positive sediment budget?
When more material is added to the cell than is removed - a net accretion of material
The shoreline builds towards the sea
What is a negative sediment budget?
More material is removed from the sediment cell than is added
Shoreline retreats landwards
What are marine processes?
A geomorphological process hat operates upon the coastline that are connected with the sea, such as waves, tides and longshore drift
What are sub aerial processes?
A geomorphological process that operates on the land but affects the shape of the coastline, such as, weathering,mass movement and run-off
What are the main coastal processes?
Mass-movement Weathering Erosion Deposition Transport
What are the main processes of marine erosion?
Hydraulic Action Wave quarrying Abrasion/corrosion Attrition Solution
What factors affect the rate of coastal erosion?
Wave steepness FetchSea depth Coastal configuraton Human activity Beach presence/profile
Wha is lithology?
The characteristics of the rock - it’s resistance to erosion and permeability, it’s structure and variation
What is a Concordant coastline?
Whe the rock types run parallel to the sea/coastline
what is a discordant coastline?
When the rock types run perpendicular to the coast
What are the main processes of marine transportation?
Traction
Saltation
Suspension
Solution
What is aeolian deposition?
The entrainment/transportation/deposition of sediment by wind
What is surface creep?
A process similar to traction, where wind rolls or slides sand grains along the surface
What is aeolian saltation?
When the wind is strong enough to temporarily pick up sand and transport to distances up to 30m
What is sub aerial weathering?
Processes that slowly break dow th coastline by weakening rocks and allow sudden movements or erosio to happen more easily
What is mechanical/physical weathering?
Processes that depend on the nature of the climate
E.g. Freeze thaw action
what is biological weathering?
Processes that lead to the break down of rocks due to the growth of vegetation in cracks and joints in the rock thus weakening it
What is chemical weathering/
When coasts are exposed to air and moisture so chemical process can breakdown the rocks
What are some main examples of chemical weathering?
Oxidation
Hydration
Hydrolysis
Carbonation
What is oxidation?
When the oxygen dissolved in water reacts with rock minerals, forming oxides or hydroxides. It causes the rocks to disintergrate
What is carbonation?
When carbon dioxide dissolved in rainwater makes a weak carbonic acid which reacts with calcium carbonates, often found in rocks like limestone and chalk.
What factors influence mass movement?
Level of cohesion with the sediment Height and angle of the slope Sediment size Temperature Level of saturation
What are the main types of mass movement?
Landslides Rock falls Mudflows Slumping Soil creep
