2.1.1 The coastal system Flashcards
Dynamic equilibrium
Where there is an equal balance between inputs and outputs within a system.
How are coasts systems?
Coasts are systems – they have inputs, outputs, flows and stores of sediment and energy.
Negative feedback
Negative feedback is when a change in the system causes other changes that have the opposite effect – bringing it closer to dynamic equilibrium.
Positive feedback
Positive feedback is when a change in the system causes other changes that have a similar effect – bringing it further away from dynamic equilibrium.
Give an example of negative feedback in the coastal system
For example, as a beach is eroded, the cliffs behind it are exposed to wave attack. Sediment eroded from the cliffs is deposited on the beach, causing it to grow in size again.
Give an example of positive feedback in the coastal system
For example, as a beach starts to form it slows down waves, which can cause more sediment to be deposited, increasing the size of the beach. The new equilibrium is reached when long-term growth of the beach stops.
What are factors affecting coastal zones?
High-energy coastlines
High-energy coasts receive high inputs of energy in the form of large, powerful wages. These can be caused by strong wind, long fetches and steeply shelving offshore zones. High-energy coastlines tend to have sandy coves and rocky landforms (e.g. cliffs, caves, stacks and arches). The rate of erosion is often higher than the rate of deposition.
- Example: Newquay
Low-energy coastlines
Low-energy coasts receive low input of energy in the form of small, gentle waves. These can be caused by gentle winds (e.g. if the location is sheltered), short fetches and gently sloping offshore zones. Some coastlines are low energy because there is a reef or island offshore, which protects the coast from the full power of waves. Low-energy coastlines often have saltmarshes and tidal mudflats. The rate of deposition is often higher than the rate of erosion.
- Example: Northumberland Coastline, UK
What are the different ways coasts can be classified?
- Geology: Which can create rocky, sandy and estuarine coasts, as well as concordant and discordant coasts.
- Energy: Levels of wave energy create high or low energy coastlines. Constructive vs destructive waves.
- Balance: Between erosion and deposition creating either erosional or depositional coasts.
- Sea level: Changes in sea level create either emergent or submergent coastlines.
But no classification is definitive. Cornwall has a high-energy coast which is mostly rocky, but also has long stretches of sand. Similarly, the low-lying coasts of eastern/southern England still have high cliffs at points.
Geology
Which can create rocky, sandy and estuarine coasts, as well as concordant and discordant coasts.
Erosion
The wearing away of the Earth’s surface by the mechanical action of processes of glaciers, wind, rivers, marine waves and wind.
Fetch
Refers to the distance over open water which a wind blows uninterrupted.
Tides
The periodic rise and fall of the level of the sea in response to gravitational pull from the sun and moon.
Mass movement
The movement of material downhill under the influence of gravity but may also be assisted by rainfall.
