3 Coastal systems and landscapes Flashcards
What are coasts?
They are natural systems - they have inputs, outputs, flows, stores of sediment and energy.
What is a negative feedback loop?
It is when a change in the system causes other changes that have the opposite effect. 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.
What is a positive feedback loop?
It is when a change in the system causes changes that have a similar effect. For example, as a beach starts to form it slows down waves, which can cause more sediment to be deposited increasing the beach size.
How is wind created?
It is created by air moving from areas of high pressure to areas of low pressure. During events such as storms, the pressure gradient is high and winds can be very strong.
How are waves created?
Waves are created by the wind blowing over the surface of the sea. the friction between the wind and the surface pf the sea gives the water a circular motion. As waves approach the shore they break. Friction with the sea bed slows the bottom of the wave and makes their motion more elliptical. the crest of the wave rises up and then collapses.
What is the swash?
The movement of water up the beach.
What is backwash?
The movement of water back towards to sea.
What is a constructive wave?
They have a low frequency. They’re low and long which gives them a more elliptical cross profile. The powerful swash carries material up the beach and deposits it.
What is a destructive wave?
They have a high frequency. They’re high and steep, with a more circular cross profile. The strong backwash removes material from the beach.
What are tides?
Tides are periodic rise and fall of the ocean surface, caused by the gravitational pull of the Moon and the Sun.
What are currents?
A current is the general flow of water in one direction - it can be caused by wind or by variations in water temperature and salinity. Currents move material along the coast.
What are high energy coasts?
High-energy coasts receive high inputs in the form of large, powerful waves. These can be caused by strong winds, long fetches and steeply shelving offshore zones. They tend to have sandy coves and rocky landforms. the rate of erosion if often higher than the rate of deposition.
What are low energy coasts?
Low energy coasts receive low inputs of energy in the form of small, gentle waves. These can be caused by gentle winds, 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 the waves. They have saltmarshes and tidal mudflats. the rate of deposition is greater then the rate of erosion.
What is a sediment budget?
it is the differences between the amount of sediment that enters and the amount that leaves. If more enters than leaves, it’s a positive sediment budget and the coastline builds up. If more sediment leaves then enters, it’s a negative sediment budget and the coastline retreats.
What is a sediment cell?
The coast is divided into sediment cells. They are lengths of coastline that are pretty much entirely self-contained for the movement of sediment. This means that processes going on in one cell don’t affect the movement of sediment in another cell - each cell is a closed coastal system.
What is erosion?
It’s the action of removing material from one place to another.
What is corrasion (abrasion)?
Bits of rock and sediment transported by the waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces,
What is hydraulic action?
Air in cracks in cliffs is compressed when waves crash in. The pressure is exerted by the compressed air breaks off rock pieces.
What is wave quarrying?
The energy of a wave as it breaks against a cliff enough to detach bits of rock.
What is solution (corrosion)?
Soluble rocks get gradually dissolved by the seawater.
What is attrition?
Bits of rock in the water smash against each other and break into smaller bits.
What is transportation?
the process of eroded material being moved.
What is solution (transportation)?
Substances that can dissolve are carried along the in the water.
What is saltation?
Larger particles, such as pebbles or gravel, are too heavy to be carried in suspension. Instead, the force of the water causes them to bounce along the sea bed.