Geography coasts

system definition and elements:

a group of interrelated processes that operate simultaneously in the physical landscape

a system contains elements of:

1. a functioning set of components

2. a flow of energy which powers said components

3. a process for internal regulating known as feedback

what makes up a system:

inputs - matter is added to the system

outputs - matter is removed from the system

stores - the accumulation of matter in a space

flows - the movement of matter

boundaries - edges of systems

key coastal system attributes:

processes - marine, terrestrial, atmospheric and biological mechanisms which move material between stores

controls - the given of the coastal environment - climate, geology, rock structure, sea level, all subject to change 

landscape components - physical features of erosion and deposition that are shaped by systems but may also contribute to inputs and receive outputs

dynamic equilibrium

when the system is in a steady state, where it is not growing or reducing so it is balanced - inputs = outputs

feedback loops 

where processea are not in balance so either an increase or decrease

negative - the chnage is not amplified e.g. cliff erosion causing slumping, reducing cliff retreat 

positive - the change amplifies the change in cycle e.g.erosion wears limestone, adds more rocks to sea, more rocks thrown at cliff

difference between landform and landscape

land form - a natural feature of the earth’s surface

landscape - ALL the visable features of an area of land, often a areas aesthetic appeal

define each shore zone

breaker zone - where waves break at the coast due to increased friction with the seabed, slowing and shortening wavelength 

nearshore zone - the area of shallow water beyond the low tide mark where waves first interact with the seabed, causing them to steepen, break and reform while surging to the beach

swash zone - the area where incoming broken waves rush up as the ‘swash’ which is the land-ocean boundary where the water mark fluxuates often

offshore zone - the zone going seaward from the point of low tide to the depth of the wave base level or to the outer edge of the continental shelf

foreshore - the internal zone of the coast defined with high tide

back shore - often dry area which is only affected during large storm events

the formation of waves: 

• wind transfers it’s energy to the surface of the sea

• this causes frictional drag which disturbs the surface, forming ripples 

• if on open sea, there is little horizontal movement of water, rather an orbital motion, causing oscillatory waves 

• near to the coast, horizontal movement of water does occur as waves are driven onshore, known as translatory waves 

• less shallow water means waves become more epiletical as friction acts on the water 

• the wavelength and the velocity decreases where the wave height increases

• causing water to back up behind and rise to the point where it topples over 

destrucive waves

• high energy

• strong backwash, removing undesired sand

• weak swash brings it further in shore

constructive wave

• low energy, meaning lower wave frequency

• strong wash carries strong constructive elements

• weak backwash takes time to remove sand 

• forms a wide sloping beach 

Fetch definition

the distance of open water over which the wind blows uninterrupted in a single direction, creating waves

tides

• tides are caused by the effect of gravity from the moon and (less so) the sun acting on the earth.

• one ocean bulge is expected on the side of the earth facing the moon, with

• another one on the other size of the earth at the same time, between them on the sides, the sea is lower, creating low-tide

• high tides happen approximately twice a day, for the sun and the moon

  • this effect is strongest when the earth and the moon are in line with earth, this happens when there is a full moon and new moon

tidal ranger and intertidal zone

tidal range - the vertical difference in height of sea level between high and low tide. it varies with the monthly lunar cycle and is at its maximum with spring tide conditions

intertidal zone - the shoreline between the highest and lowest spring tides; it is where the predominant wave activity occurs so is subject to most marine erosion transfers and deposition

high energy coast

a coastline subject to maximum inputs, likely to be dynamic

• strong coast with strong waves

• long fetch

• winds that approach from a consisten onshore direction

• low pressure

• large tidal range

• many inputs of energy sources

  • erosion and transpiration common

low energy coast

a coastline that has key inputs, transfers and outputs in balance and is more likely to be in a state of stable equilibrium 

• less poweful / no waves

• short fetch 

• varied wind direction or offshore winds 

• less extreme air pressure gradients 

• gentle tidal range 

• few inputs of energy 

• deposition