Coastal landscapes Flashcards
List the charecterics of destructive waves
- Destructive waves are created in storm conditions.
- They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
- They occur when wave energy is high and the wave has travelled over a long fetch.
- They tend to erode the coast.
- They have a stronger backwash than swash.
- They have a short wave length and are high and steep.
List the charecteritics of constructive waves
- They are created in calm weather and are less powerful than destructive waves.
- They break on the shore and deposit material, building up beaches.
- They have a swash that is stronger than the backwash.
- They have a long wavelength, and are low in height.
Give details of the four types of erosion that happen in coastal areas
- Hydraulic action. Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
- Abrasion. Bits of rock and sand in waves grind down cliff surfaces like sandpaper.
- Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
- Corrosion. Acids contained in sea water will dissolve some types of rock such as chalk or limestone.
With use of this diagram explain the process of longshore drift
The transport of sand and pebbles along the coast is called longshore drift.
The prevailing wind (the direction the wind ususally blows from) causes waves to approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle (usually 45º). The backwash, however carries the material back down the beach at right angles (90°) as this is the steepest gradient.
if a pebble was placed in the water it would be carried along the coastline in a zig-zag motion and would eventually be deposited when the waves lose energy.
The general direction of longshore drift is decided by the prevailing wind. In the diagram below the prevailing wind is approaching from the south-west. Therefore longshore drift is moving material from the west to the east.
Name three factors which affect rates of coastal change
The impact of extreme weather events
Geoglogy - the character of local rocks
The consequences of human intervention - e.g. if groynes built in one place it will affect another place
Describe how groynes help protect a coastline
They interrupt the movement of sediment.
Usually made out of wood, concrete or stone.
Groynes create beaches or prevent them being washed away by longshore drift.
Why might some people living along the coastline from a town with groynes be oppossed to them?
If sediment is trapped in front of one settlement it will not move along the coast to the next settlement. This means that the place without groynes will be at an increased risk of erosion
Name some hard engineering strategies for preventing coastal erosion
Sea wall
Gabions
Rock armour
Groynes
Revetments
Describe the benefits of ‘beach replinishment’?
Beach nourishment is the process of dumping or pumping sand from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach. Beach nourishment does not stop erosion, it simply gives the erosional forces (usually waves) something else to “chew on” for awhile
Describe how a spit is formed
Longshore drift moves material along the coastline
Swash moves material up the beach in the direction of the prevailing wind
Backwash brings it back down the beach at rightangles
A spit forms when the material is deposited
Deposition occurs when an obstacle stops the material moving any further e.g. a river or a headland
Over time, the spit grows and develops a hook if wind direction changes further out.
Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.
Name as many coastal landforms created by erosion as you can
Wave cut platform
Caves
Arch
Stack
Stump
Headland
Bay
You will need to know how each of these are formed as well
