Coastal Landscapes Flashcards
What is weathering?
Weathering is the breakdown of rocks at or near to the surface of the ground.
How many types of weathering is the and what are they?
3 and chemical, biological and mechanical
What is chemical weathering?
Rainwater is slightly acidic. When rainfalls on rocks such as limestone and chalk a weak chemical reaction takes place cause ing the rock to weaken and break down
What is biological weathering?
The roots of growing plants can widen cracks in rocks. Burrowing animals and nesting birds in cliff faces can also cause the rock to weaken and decay
What is mechanical weathering?
This is caused by the repeated freezing and thawing of water in a crack or hole in the rock. When water freezes, it expands by about 10%, causing stresses within the rock. When the ice melts, water seeps deeper into the rock along the deepened crack. After repeated cycles of freezing and thawing, fragments of rock may break off
What is mass movement on the coast?
Mass movement is the downslope movement of rocks and soil from the cliff top under the influence of gravity
What do types of mass movement are there?
When rocks fall, slumping and sliding
What are the 4 different ways waves can erode the coast?
Abrasion, hydraulic action, attrition, solution
What is abrasion?
It’s when fragments of rock, pebbles and sand are picked up by the waves and thrown against the cliff face, causing pieces of rock to break off
What is hydraulic action?
When waves crash against the cliff, the impact, force and weight of the water against the rocks wears away the rocks. It also compresses air in joints and faults in the rock, causing pressure to build and loose rocks to be dislodged. As the waves retreat, the compressed air is released, often explosively, causing the rock to weaken further
What is attrition?
Rocks fragments and pebbles carried by the waves are reduced in size as they collide against each other and the cliff face. They are eventually broken down into sand-sized particles, which are more easily transported by waves
What is solution?
This is the chemical action on rocks by seawater. It is most effective on limestone rocks, in which calcium is dissolved and carried away in solution
What do loose wet rocks do?
Slump under the gravity along the curved slip planes
When does slumping happen?
It happens when the rock is saturated. Loose wet rocks slump down under the pull of gravity along curved slip planes
When does slumping often occur?
On clay coasts
Transportation
The eroded material will be transported along the coastline by different processes depending on the size of the material and the amount of energy in the waves: the four methods are traction, saltation, suspension and solution. The transport of sand and pebbles along the coast by waves is called longshore drift
How does longshore drift occur?
Waves approaching the coast carry sand and pebbles. Longshore drift is the process of transportation which moves sand and pebbles along the coast. Waves often approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle as the wave. The backwash then draws the sediment back down the beach at right angles to the coastline, as this is the steepest gradient. The process is repeated resulting in a zigzag movement of sediment around the goats of the UK is controlled by the direction of the prevailing wind
What is longshore drift?
The transportation of sand and pebbles
What are the 4 different ways waves transport material?
Traction, saltation, suspension and solution
What does traction do?
(Wave transport) large boulders are rolled along the sea bed by waves
What is saltation
(Wave transport) smaller stones are bounced along the seabed
What is suspension?
(Wave transport) sand and small particles are carried along the flow
What is solution?
(Wave transport) some minerals are dissolved in seawater and carried along the flow
How is the coastal landscape shaped?
By the interaction of the different physical processes of weathering, mass movement and erosion
Name 3 types of soft rock
Mudstone
Sands
Clays
How are destructive waves formed?
Destructive waves are formed by strong winds that have blown over large fetch areas. The waves are powerful and lead to coastal erosion. Destructive waves are tall and steep, they are closely spaced and break frequently - typically between 11-15 waves break per minute, the back wash is much stronger than the swash, so rocks, pebbles and sand are carried back out to sea. If beaches form, they tend to be narrow and steep and offer cliffs little in the way of protection as they cannot absorb much of the wave energy
What are constructive waves?
Constructive waves are associated with light winds. The waves have less energy and encourage deposition. They are low in height and widely spaced, breaking gently - typically 6 - 9 waves break per minute. The swash is stronger than the backwash, so more material is carried up the beach than is removed. The resulting beaches tend to be wide and shallow, and they help protect the cliffs from erosion as the wave energy is absorbed by the beach
What does the unpredictability of the uk’s weather and climate affect?
The rates of coastal erosion retreat, impacting on landforms and landscapes
What is the different impacts do coastal erosion have due to?
The four seasons, for example, cd temperatures in winter lead to freeze-thaw weathering
What are the effects of stormy weather
Storm frequency is high in many parts of the UK
Coasts are often subject to strong winds, increasing the eroding power of the waves, and heavy rainfall contributes to the mass movements
Frequent storms can damage coastal landforms like spits. Spurn head along the Holderness coast is at risk of being cut off from the mainland
Beach sediment can be removed from a reaction of coastline
Sand dunes can be removed by storms
where do prevailing winds come from in the uk?
The south-west
What does prevailing wind from the south-west bring?
It brings warm moist air from the Atlantic and frequent rainfall,Munich contributes to weathering and mass movement on the coast
What is the definition of coastal erosion?
Coastal erosion is the removal of material from the coast by wave action, causing the coastline to retreat inland called coastal recession. This results in loss of land and damage to buildings, roads and railways and can increase the risk of coastal flooding
What is the definition of coastal retreat?
When coastal erosion causes the coastline to move further inland
Explain how the uk’s climate contributes to coastal erosion
The uk’s climate is temperate maritime,Monica means winters are mild and and and summers are warm and wet. The prevailing wind from the south-west often brings rainfall to the country. The large amount of rainfall causes coastlines to be eroded through weathering, and can lead to mass movement and cliff collapse,Mohicans lead to coastal retreat. Storm frequency is high, which brings heavy rainfall and strong winds that increase the erosional power of waves. The seasonal nature of the climate means that rocks in the coast are subject to freeze-thaw weathering in winter, which adds to erosion
What distinctive landforms are there that have been caused by coastal erosion?
Headlands, bays, headland features and wave-cut platforms
Where do headlands and bays develop?
On coastlines with a mix of hard and soft rock
How are headlands and bays formed?
Hydraulic action and abrasion erode sea cliff. On a discordant coast they erode at varying rates as rocks of different hardness and resistance meet the sea. The stronger or harder rocks, such as chalk and of stone are able to resist wave attacks and erosion for longer. These sections of cliff stand out as prominent rocky headlands.
The softer or weaker rocks, such as the mudstones and siltstones are eroded back more quickly to form bays
Hard rocks like chalk are often left jutting out in sea, forming what?
Headlands
Soft rocks such a sands are eroded more quickly forming what?
Bays
Define cliffs
Cliffs are common coastal features. Cliffs are shaped through weathering and erosion. Soft rock erodes easily to creat gently sloping cliffs. Hard rock erodes more slowly to create steep cliffs
When are stacks formed?
Continued erosion by the sea widens the arch. As the sea undercuts the base of the arch, more pressure is placed on top of the arch. Eventually the weakened roof of the arch collapses, leaving a stack, a pinnacle of rock, separated from the mainland.
Further erosion and weathering over time may cause the stack to collapse to leave a small, flat stump, which is often covered by high tide
When is a cave formed?
As destructive waves break against the headland, any lines of weakness in the rock such as joints or faults are attacked. Through hydraulic action and abrasion, the waves erode the rock along the joint or fault which will increase in size and may eventually form a cave
When is an arch formed?
Waves continue to erode caves, in particular through hydraulic action. When a wave breaks, it blocks off the entrance to the cave and traps air within it. The trapped air is compressed, increasing the pressure on the sides, roof and back wall of the cave. If the cave forms part of a narrow headland, the pressure from the waves may result in the back of the cave becoming pushed through the other side. The cave then becomes a natural arch as it is open on both sides
What can the erosion of cliffs create?
Wave-cut platforms
What are wave-cut platforms?
A gently sloping rocky area is left at the bottom of the retreating cliff. The platform is covered at high tide but exposed at low tide. It’s surface is not smooth because differences in rock structure are picked out by abrasion to create many grooves, rock pools and ridges within the bare rock
What causes the formation of distinctive landforms including beaches, spits and bars
The process of deposition
What are beaches accumulations of?
Sand and shingle formed by deposition and shaped by erosion,transportation and deposition
What are can beaches be?
Straight or curved
Have are curved beaches formed?
By waves refracting, or bending, as they enter a bay
What can beaches have on them?
Sand or pebbles (shingle)
Where are shingle beaches usually found?
Found where cliffs are being eroded and where waves are powerful