The Coastal System
The coast can be seen as a system in order to help to understand the processes and interactions involved. In theory, the inputs, processes and outputs work together to create coastal equilibrium. However, as we will see in this unit human actions affect the state of equilibrium within the coastal system. Coastal landscapes are open systems. This means energy and matter can enter and leave the system.
Marine – waves, tides and currents
Energy – kinetic energy from waves and wind, thermal energy from the sun and potential energy from material on cliffs/slopes and material from processes of weathering, mass movement, erosion and deposition
Geological – rock type, structure and tectonics. material from marine deposition, weathering and mass movement
Atmospheric – climate, weather and climate change
People – urban planning, housing, industry, coastal management/defences, leisure
Stores such as sediment on a beach, and flows (transfers), such as longshore drift moving sediment along the coast.
Erosion – attrition, corrasion/abrasion, hydraulic action
Weathering – freeze-thaw, solution, salt crystallisation
Mass Movement e.g. slumps, soil creep and slides
Marine and wind erosion as well as evaporation.
Landforms of erosion – cracks, caves, stacks, stumps, wave-cut platforms, blowholes
Landforms of deposition – beaches, spits, tombolos, sand dunes, salt marshes
If inputs and outputs within a coastal system are the same then a state of equilibrium exists. An example of this would be when the rate of sediment being added to a beach is the same as the amount leaving the beach resulting in the beach remaining the same size. If something happens the break this equilibrium the system will change to restore the equilibrium. This is known as dynamic equilibrium, as the system responds to the disturbance.
When an initial change within a system brings about further change in the same direction this is known as positive feedback.When a system returns to equilibrium following a change in the system this is known as negative feedback.
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