Coastal Systems and landscapes Flashcards
Coasts are systems. What are the systems made up of?
Inputs-sediment can be brought into a system in various ways also with energy inputs from wind, waves, tides and currents.
Outputs-sediment can be washed out to sea or deposited further along the coast.
Flows/Transfers-processes such as erosion, weathering, transportation and deposition can move sediment within the system.
Stores-landforms such as beaches, dunes and spits are stores of sediment
Outline negative feedback within a coastal system
Negative feedback is when a change in the system causes other changes with the opposite effect. For example, as the beach is eroded, the cliffs behind it are exposed to wave attacks. Sediment eroded from the cliffs is deposited on the beach, causing it to grow in size again.
Outline positive feedback within a coastal system
A positive feedback is when a change in the system causes other 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 size of the beach. The new equilibrium is reached when long-term growth of the beach stops.
Outline wind as a source of energy
Winds are created by air moving from areas of high pressure to areas of low pressure.
Strong winds can generate powerful waves. In some areas, wind consistently blows from the same direction (this is called a prevailing wind)- this causes higher-energy waves than winds that change direction frequently
Ouline Tides as an energy input
Tides are the periodic rise and fall of the ocean surface caused by the gravitational pull of the moon and the sun.
Tides affect the position at which waves break on the beach.
Outline currents as an energy input.
A current is the general flow of water in one direction- it can be caused by wind or by variation in water temperature and salinity.
Currents move material along the coast.
outline waves as an energy input
constructive waves are low frequency(only around 6-8 waves per minute).They’re low and long, which gives them a more elliptical cross profile. The powerful swash carries material up the beach and deposits it.
Destructive waves are high and steep, with a more circular cross profile. They have a higher frequency(10-14 waves a minute). The strong backwash removes material from the beach.
What is a high-energy coast
High-energy coasts receive high-energy inputs in the form of large, powerful waves. These can be caused by strong winds, long fetches and steeply shelving offshore zones. High-energy coastlines 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
What is low-energy coast
Low energy coast receives 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 waves.The rate of deposition is often higher than the rate of erosion
Outline inputs of sediment into a coastal system.
Rivers carry eroded sediment into the coastal system from inland
sea level rise can flood river valleys, forming estuaries
sediment is eroded from cliffs by waves, weathering and landslides
Waves, tides and currents can transport sediment into the coastal zone from offshore deposits.
Difference between positive and negative sediment budget
If more sediment enters than leaves,its a positive sediment budget and overall, the coastline builds outward, whereas if more sediment leaves than enters,its a negative sediment budget and overall, the coastline retreats.
What are sediment cells
These are lengths of coastline that are pretty much entirely self-contained for the movement of sediment(sediment doesn’t move between cells). This means that processes going in one cell don’t affect the movement of sediment in another cell-each cell is a closed coastal system.
What is a fetch
The distance of open water over which a wind blows uninterrupted by major land obstacles-length of fetch helps to determine the magnitude and energy of waves
What are the 5 main ways to erode the coastline
Abrasion-bit of rock and sediment transported by the waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces.
Hydraulic action- air in cracks in cliffs is compressed when waves crash in. The pressure exerted by the compressed air breaks off rock pieces.
Wave quarrying-The energy of a wave as it breaks against a cliff is enough to detach bits of rocks.
Solution-Soluble rocks get gradually dissolved by seawater.
Attrition-Bits of rock in the water smash against each other and break into smaller bits.
Transportation processes of eroded material
Solution-substances that can dissolve are carried along in the water(limestone is dissolved into slightly acidic water)
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 seabed.
Suspension-Very fine material, such as silt and clay particles, is whipped up by turbulence(swirling of water) and carried along in the water.most eroded material is transported this way.
Traction-Very large particles, boulders are pushed along the sea bed by the force of the water
