coasts Flashcards
What are the inputs of a coast
sediment
Energy inputs come from wind, waves, tides and currents
What are the outputs of a coast
sediment can be washed out to sea or deposited further along the coast
What are the flows/transfers of a coast
erosion, weathering, transportation and deposition
What are the stores in a coast
landforms such as beaches, dunes, spits
An example of negative feedback
- When the destructive waves from the storm lose their energy excess sediment is deposited as an offshore bar
- The bar dissipates the waves energy which protects the beach from further erosion
- Overtime the bar gets eroded instead of the beach
- Once the bar has gone normal conditions ensue and the system goes back to dynamic equilibrium
An example of positive feedback
1.People walking over sand dunes destroys vegetation growing there and causes erosion
2. As the roots from the vegetation have been holding the sand dunes together, damaging the vegetation makes the sand dunes more susceptible to erosion. This increases rate of erosion
3. Eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from its original state.
What are the characteristics of a constructive wave
low frequency
weak backwash
strong swash
elliptical cross profile
deposits material
low and long
What are the characteristics of a destructive wave
high frequency
strong backwash
weak swash
circular cross profile
removes material
high and steep
What are tides controlled by
the gravitational pull of the moon and sun
What are high energy coasts
receive high inputs of energy in the form of large, powerful waves.
Tend to have sandy coastlines and rocky landforms
The rate of erosion is higher than rate of deposition
What are low energy coastlines
receive low inputs of energy in the form of small, gentle waves
usually low energy due to reefs or islands offshore
often have saltmarshes and tidal mudflats
rate of deposition is often higher than rate of erosion
What is a sediment budget
the difference in amount of sediment that enters a system and the amount that leaves
What is a positive sediment budget
more sediment enters than leaves
What is a negative sediment budget
more sediment leaves than enters
What are the number of sediment cells in england and wales
11
What is a sediment cell
length of coastline that is entirely self contained for the movement of sediment.
closed coastal system
what is abrasion
bits of rock and sediment transported by the waves that smash and grind against rocks and cliffs, smoothing the surface
What is hydraulic action
air in cracks in cliffs is compressed when eaves crash.
The pressure exerted by the compressed air breaks off rock pieces
What is cavitation
As waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off
What is wave quarrying
The energy of a wave as it breaks against a cliff is enough to detach bits of rock
What is corrosion
soluble rock 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 solution
Substances that can dissolve are carried along in the water
e.g limestone
What is suspension
very fine material, such as clay and silt, is whipped up by the erratic swirling of water and carried along in the water
What 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
What is traction
Very large particles are pushed along the sea bed by the force of the water
Describe the process of littoral drift
Swash carries sediment up the beach, parallel to the prevailing wind. Backwash carries sediment back down the beach at the right angles to the shoreline
When there’s an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along the shoreline
What are the types of deposition
Marine and aeolian
What is aeolian deposition
When sediment is carried by the wind and deposited
steps to salt weathering
Caused y saline water
Saline water enters pores or cracks in rocks at high tide
As the tide goes out the rocks dry and water evaporates, forming salt crystals. As the salt crystals from they expand, exerting pressure on the rock-this causes pieces to fall out
steps to freeze-thaw weathering
It occurs in areas where temperatures fluctuate above and below freezing
Water enters the joints and crevices in the rocks
If the temperature drops below 0, the water in the cracks freezes and expands
Over time, repeated freeze-thaw actions weaken the rocks and causes pieces to fall off
steps to chemical weathering
chemical weathering is the breakdown of rock by changing its chemical composition
FOR EXAMPLE, co2 in the atmosphere dissolves in rainwater, forming a weak carbonic acid. This acid reacts with rocks that contain calcium carbonate(limestone)
What is mass movement
the shifting of material downhill due to gravity. Most likely to occur when cliffs are undercut by wave action-causing an unsupported overhang
description of sliding
material shifts in a straight line
description of slumping
material shifts with rotation
description of rockfall
material breaks up and falls
description of mudflows
material is saturated and flows downslope
How are cliffs and wave-cut platforms created
cliffs form as the sea erodes the land. Overtime, cliffs retreat due to the action of waves and weathering
weathering and hydraulic action and abrasion causes a notch to form at the high water mark. This eventually creates a cave
Rock above the cave becomes unstable with nothing to support its weight, and it collapses
Wave-cut platforms are flat surfaces left behind at the low water mark
How are headlands and bays created
They form where there are bands of alternating hard rock
