Coasts - Systems & Processes Flashcards
What is the backshore?
Backshore is the area between the high water mark and tha landward limit of marine activity. Changes noramlly take place here only during storm activity.
What is the foreshore?
Foreshore is the area lying between the high water mark. It is the most important zone for marine processes in times that are not influenced by storm activity.
What is the inshore?
The area between the low water mark and the point where waves cease to have any influence on the land beneath them.
What is the offshore?
The area beyond the point where waves to cease to impact upon the seabed and in which acitivity is limited to deposition of sediment.
What is the nearshore?
Nearshore is the area extending seaward from the high water mark to the area where waves begin to break. It includes: the swash zone, surf zone and breaker zone.
What is the swash zone?
The area where a turbulent layer of water washes up the beach following the breaking of a wave.
What is the surf zone?
The area between the point where waves break, forming a foamy, bubbly surface and where the waves then move up the beach as swash in the swash zone.
What is the breaker zone?
The area where waves approaching the coastliune begin to break, usually where the water depth is 5 to 10m.
What are some examples of inputs in a coastal system?
1) Energy from waves, wind, tides and sea currents.
2) Sediment
3) Geology
4) Sea level change
What are the components in a coastal system?
Characteristic erosional and depositional coastal landforms
What are some example of outputs in a coastal system?
1) Dissipation of wave energy.
2) Accumulation of sediment above the tidal limit.
3) Sediment removed beyond local sediment cells.
Define erosion
The wearing away of the Earth’s surface by the mechanical action of processes of glaciers, wind, rivers, marine waves and wind.
Define fetch
Refers to the distance of open water over which a wind blows uninterrupted by major land obstacles. The length of fetch helps to determine the magnitude and energy of waves reaching the coast.
Define mass movement
The movement of material downhill under the influence of gravity, but may also be assisted by rainfall.
Define weathering
The breakdown and/or decay of rock at or near the Earth’s surface creating free sodil material that remains in situ intil it is moved by later erosional processes. Weathering can be mechanical, biological/organic or chemical.
What are the features of wind as an input into a coastal system?
1) Spatial variations in energy result from variations in the strength and duration of the wind.
2) The length of fetch helps to determine the magnitude and energy of waves reaching the coast.
3) The energy acquired by waves depends upon the strength of the wind, the length of time it is blowing and the fetch.
4) Wind acts as an agent of erosion as it can firstly pick up and remove sediment from the coastline and use it to then erode other features.
Define waveheight/amplitude
This is the height difference between a wave creast and the neighbouring trough.
Define wavelength
This is the distance between successive crests.
Define wave period
This is the time for one wave to travel the distance of one wavelength, or the time between one crest and the following creast passing a fixed point.
Define backwash
The action of water receding back down the beach towards the sea.
What are constructive waves?
Waves with a low wave height, but with a long wavelength and low frequency of around 6-8/min. Their swash tends to be more powerful than their backwash and as a consequence beach material is built up.
What are destrcutive waves?
Waves with a heigh wave height with a steep form and high frequency of 10-14/min. Their backwash is genrally stronger than their swash, so more sediemnt is removed than is added.
Define swash
The rush of water up the beach after a wave breaks
What are longshore currents?
Longshore currents occur as most waves do not hit the coastline ‘head on’ but approach at an angle to the shoreline. This generates a flow of water running parallel to the shoreline. This not only moves water along the surf zone but also transports sediment parallel to the shoreline.