coastal systems Flashcards
(43 cards)
what are inputs
sediment can be brought into the system in various ways. energy inputs come from wind, waves, tides and currents.
flows
processes such as erosion, transportation and deposition can move sediment within the system.
stores
landforms such as beaches, dunes and spits are stores of sediment.
what is a negative feedback?
when change in the system causes other changes that have the opposite effect. For examples a beach is eroded the cliffs behind are exposed to erosion, sediment eroded from the cliffs is then deposited on the beach, causing it to grow in size again.
positive feedback
when change in the system causes other changes that have a similar effect. e.g. as a beach grows the waves lose energy so deposit more sediment.
sources of energy (wind)
-winds are created by moving from areas of high pressure to areas of low pressure.
-strong winds generate powerful waves.
sources of energy (waves)
- waves are created by wind blowing over the sea, the friction gives the wave its circular motion.
-the effect of the wave depends on wind speed and fetch.
-as the waves break, friction with the sea bed slows the bottom of the waves.
sources of energy (tides)
-tides are the periodic rise and fall of ocean surface caused by the gravitational pull of the moon and the sun.
- tides affect the position at which waves break on the beach ( at high tide they break higher up shore.
sources of energy (currents)
- a current is the general flow of water in one direction- it can be caused by wind or variations in water temperature and salinity.
-currents move sediment down the coast (LSD).
what are high energy coasts?
they receive inputs of energy in the form of large, powerful waves. these can be caused by strong wind, long fetches and steeply shelving offshore zones high energy coasts tend to have sandy coves and rocky landforms, e.g.cliffs caves stacks and arches.
inputs of sediment into the coastal system
-rivers carry eroded sediment into the coastal system from inland.
-From eroded cliffs
-can be formed from the crushed shells of marine organisms
-waves tides and currents can transport sediment into the coastal zones.
what is abrasion
rocks smash and grind on the coast, slowly eroding it and smoothing surfaces.
what is cavitation
the compressed air expands violently, exerting pressure on the rock and causing pieces to break off.
what is wave quarrying?
the energy of a wave as it breaks on a cliff is enough to erode it.
solution
soluble rocks such as chalk or limestone can gradually be dissolved by seawater.
what is attrition?
bits of rock in the water smash against each other and break into smaller bits.
what is solution (transportation)
Substances that can dissolve are carried along in the water.
what is suspension (transportation)?
very fine materials such as silt and clay particles, is whipped up by turbulence and carried along in the water.
what is saltation (transportation)?
larger particles such as pebbles or gravel, are too heavy to be carried in suspension instead the force of the water bounces them along the surface of the water.
when does deposition occur ?
deposition occurs when the load of the sediment exceeds the ability of the wind or waves to carry it.
-friction increases if waves enter shallow water or wind reaches land, this lowers energy.
-flow becomes turbulent and encounters an obstacle.
what is salt weathering?
salty water (saline) enters pores or cracks in rocks at high tide. as the tide goes out and the water evaporates, forming salt crystals which exert pressure on the rock- this cause pieces to fall off.
freeze thaw weathering
frozen water expands.
what is chemical weathering
the breakdown of rock by changing its chemical composition. acidic rain containing carbonic acid .
what cause mass movements?
-unconsolidated rocks (clay are prone to collapse as there’s little friction.
-Heavy rain can saturate unconsolidated rock, further reducing friction and making it more likely to collapse.
-runoff can erode fine particles and transport them down slope.
