Coasts Flashcards
Why is the coast classed as an open system ?
The coast is classed as an open system because it receives inputs and transfers outputs into the coastal system.
e.g sediment carried into coast by a river eroded rock material trasnported offshore
What are inputs of a coastal system?
Inputs are material or energy moving into the system from the outside
eg. precipitation and wind
What is coastal energy?
Coastal energy
What are coastal stores/components?
Coastal stores and components are the indiviual elements/parts of a system E.G beach es, sand dunes, nearshore sediment
What is erosion?
Erosion is the wearing away of earths surface by the mechanical action of processes of glaciers, wind, rivers, marine waves and wind.
What is fetch?
A stretch of open water which the wind blows
Fetch refers to the distance of open water over which a wind blows uninterrupted by major lane obstacles. The length of the fetch helps to determine the magnitude (size) and energy of the waves reaching the coast.
Why is the coastal system important?
The coastal system is important because
- 50% of the worlds population live in coastal areas.
-75% of all large cities are coastal
-the enviroment is used for many things
-the coastal system is dynamic
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What is dynamic equilibrium?
Dynamic Equilibrium represents a state of balance in an everchanging system.
e.g constructive waves build up a beach making it steeper this leads to the formation of destructive waves that plunge rather than surge
What are stores/components?
Stores/components are the individual elements/ parts of a system.
e.g beaches is a store/sink
What is a flow/transfer?
A flow/transfer are the links or relationships between components
e.g wind blown sand, mass movement processes.
What is positive feedback?
Positive feedback is where a flow/transfer leads to an increase or growth
e.g coastal management can Inadvertently lead to an . increase in erosion
What is negative feedback?
Negative feedback is when a flow/transfer to a decrease/decline
e.g when the rate of weathering and mass movement exceeds the rate of cliff foot erosion this leads to the formation of a scree slope protecting the cliff face from erosion
What are sources of energy at the coast?
- The suns energy = warms the land and sea through thermal expansion
- Wave energy = main source of energy at the coast
-Wind energy = winds are caused by moving air from high to low pressure and the bigger the pressure difference the stronger the wind
What factors affect wave energy?
- The strength of the wind - determined by the pressure gradient
- The duration of the wind - the longer the wind blows the more powerful the waves will become
Where in the UK are the biggest waves?
Cornwall has the biggest waves because of the dominant prevailing wind facing the coastlines has a large fetch creating stronger waves
What is storm surge and its role?
Storm surge = is a rising in sea level as a result of wind and atmospheric pressure changes associated with a storm
- Storm surge is caused by low pressure
- 1mb drop = 1cm rise in water level
-Strong winds drive water onshore
-Typical in North sea (depression) and in tropical warer (tropical storms) - Excaberted by funneling
What are destructive waves?
Form during local srorms and are responsib;e for:
- Weak swash strong backwash
- Beach loss
- Usually associated with sleeper beach profile although overtime they flatten the beach
- Wave frequency 10-14 per min
How are waves formed?
- Waves are formed by the wind blowing over the surface of the ocean
- Causes disrtubance/fictional drag to the warer surface
- Forming waves ripples = waves
Waves move in orbital fashion in deep water (offshore zone) but a more elliptical motion in shallower water - The change in motion of the wave wull cause it to break
- The water becomes shallower and the circular orbit of water particles changes or elliptical shape
The wave length (distance between two cresrs ) and the velocity both decrease
Wave height increases causing water to back up from behind andrise into a point wgere it starts to topple over and break
Water rushed up the beach as swash and flows back as back wash
What are constructive waves?
Form as distant weather systems generate these waves in the open ocean:
- Strong swash, weak backwash
- Low surging waves approx 1m high long wave lenth >100m
- Beach gain
- Usually associated with a gentle beavh profile although overtime tehy build up beach making it steeper
- Wave frequenecy 6-8 per min
What are tides?
Tides are a regular rise and fall of sea levels around the globe
When the moon and sun and earth are at 90 degrees to eachother this creates a lower gravitational pull - neap tide is twice a month
What causes tides?
Todes are the rise and fall in the level of sea caused by gravitational pull of the sun and the moon and the moon has a far stronger influence as it is closer
As the moon orbits the earth, high tides follow it, in the UK we have two high tides and two low tides per day and during the high tide there is a bulge
When the sun moon and earth are in allignment creates a strong gravitational pull therefore the biggest high tide spring tide happens twice each month
What is spring tide?
When the sun moon and earth are in allignment creates a strong gravitational pull therefore the biggest high tide spring tide happens twice each month
What is neap tide?
When the moon and sun and earth are at 90 degrees to eachother this creates a lower gravitational pull - neap tide is twice a month
What is a sediment cell?
A sediment cell = is a stretch pf coasyline usually borded by two headlands where the movement of headlands is contained
What is a sediment budget?
Sediment budget = Is the balance between sediment being added to and removed from the coastal system
What are high energy coastlines?
High energy coastlines = wave energy is strong for most of the year
Dominal process = erosion exposed to large fetch
Produces headlands, arhces, stack stumps etec
Tend to be rocky
Waves can meet up to 30m height - destructive waves
What are low energy coastlines?
Low energy coastline = wave energy is weak for most of the year
Dominant process is deposition produces beaches in sheltered areas
Spits, sand dunes, large coastal exposed to small fetch
Constructive discordant coastlines
