systems and processes Flashcards
how is wind a source of energy in a coastal system
wind is created by air moving from areas of high pressure to areas of low pressure
- strong winds generate powerful waves
- prevailing winds generate high energy waves
how are waves a source of energy in a coastal system
waves are created by the wind blowing over the sea surface
-the effect a wave has on the shore depends on wave height and fetch (high windspeed and long fetch create powerful waves
constructive waves characteristics
low frequency
low and long
powerful swash
destructive waves characteristics
higher frequency
high and steep
strong backwash
how do tides a source of energy in a coastal system
the periodic rise and fall of the ocean surface caused by the moon and suns gravitational pull
- tides affect the position at which waves break on the beach and therefore the extent of erosion on the beach
- the are between maximum high tide and minimum low tide
how are currents a source of energy in a coastal system
currents are generated by the flow of water on one direction caused by wind or variations in water and salinity
rip currents: backwash is forced under the surface due to resistance from breaking waves , forming an underwater
current
-currents move material along the coast and can lead to output of sediment from the beach area
high energy coasts 7 features with example
- high inputs of energy
- large powerful waves
- strong winds due to long fetch
- greater rate of erosion
- sandy coves
- steeply shelving offshore -zones
- rocky landforms- headlands, cliffs, wave cut platforms
-e.g. north cornish coast
low energy coasts 6 features with example
- low inputs of energy
- gentle waves
- gentle winds
- greater rate of deposition
- gently sloping offshore zones
- landforms- saltmarshes, tidal mudflats, beaches, spits
-e.g. baltic sea
5 sediment sources
- rivers; carry eroded material form inland
- sea level rise: floods form estuaries that become apart of coastal systems
- cliffs: sediment eroded, e.g. Holderness coast is eroding at 2m per year, one of the fastest eroding coastlines in Europe
- organic matter: crushed shells of marine animals
- waves, tides, currents: transport sediment
define sediment budget
the difference between the amount of sediment that enters the system and the amount that leaves
a system will operate in a state of
dynamic equilibrium where input and outputs of sediment are equal.
However, human actions
and natural variation in the system can disrupt the state of equilibrium.
define sediment cells
- Coasts can be split into sections called sediment cells which are often bordered by prominent
headlands.
-Within these sections, the movement of sediment is almost contained and the flows
of sediment act in dynamic equilibrium.
-The dynamic equilibrium may be upset in the long term
by human interventions, or in the short term, they may be interrupted by natural variations.
- Within each sediment cell there are smaller subcells.
- 11 sediment cells in England
what are 6 types of erosion
- corrasion/abrasion: rock and sediment grind against rocks and cliffs and breaks of rock smoothening the cliff
- hydraulic action: air in cracks is compressed when waves crash in. the pressure causes pieces to break off
- cavitation: as waves recede the compressed air expands violently again exerting pressure on the rock and causing pieces to break off
- wave quarrying: the energy of a wave as it breaks on a cliff detaches bits of rock
- solution/corrosion: soluble rocks dissolved in water
- attrition: bits of rock smash against each other in the water and break into smaller pieces
what are 5 types of transportation
- solution: dissolved substances are carried along the water
- suspension: very fine material like silt is whipped up by turbulence and carried along the water
- saltation: larger particles like pebbles or gravel bounce along the river bed
- traction: very large particles like boulders are pushed along the sea bed
-long shore drift: swash carries sediment up the beach parallel to the prevailing wind
backwash carries it back down the beach at a right angle to the shoreline
what are 3 types of mechanical sub-Arial weathering
- salt weathering: caused by saline water that enters cracks in rock at high tide. when the tide goes out the water evaporates and forms salt crystals which expand, exerting pressure on the rock causing pieces to fall off
- freeze thaw weathering: occurs in areas where temperature fluctuates around freezing. when water gets into rocks and freezes it expands weakening the rock and causing it to fall off
- wetting and drying: rocks that contain clay expand when they get wet and the pressure causes pieces to break off
what are the 4 types of deposition: mass movement
- slides: material shifts in a straight line
- slumps: material shifts with a rotation
- rockfalls: material breaks up and falls
- mudflows: material flows downslope
