Coasts Flashcards
Define weathering
The process of rocks and artificial structures getting worn away into smaller pieces
What are the 3 types of weathering
Physical/mechanical
Biological
Chemical
Describe physical weathering
Rain water gets into cracks, freezes into ice and expands causing the rock to crack - freeze thaw
Sun heats rocks which expand in the heat, at night they contract - causing stress -Onion Skin weathering
What is biological weathering
Rocks are broken apart by growing tree roots and plants getting into cracks
What is chemical weathering
Not a mechanical process
All rain is slightly acidic and the acid reacts with the stone wearing it away/
Sulphur dioxide can make rain more acidic
How are waves formed
Waves are caused by wind dragging on the surface of the water.
The length of water the wind blows on is called the fetch.
The stronger the wind, longer it blows for and longer the fetch - the larger the waves will be and more energy they will have.
Describe constructive waves
Long + low
Less powerful
Deposit material - build beaches
6-8 per minuet
WHEN SWASH IS STRONGER THAN BACKWASH
Describe destructive waves
Strong winds Short and steep Remove material from beach 15 per minuet BACKWASH IS STRONGER THAN SWASH
Define erosion
The geological process in which materials are worn away and transported by natural forces such as wind or water. The opposite to deposition
What is the difference between weathering and erosion
Erosion involves movement and weathering is static
What is Hydraulic action
The power of the waves that smash against the rocks. Water enters cracks which then forces them to break apart
What is Abrasion
The process of wearing something away, the rocks grind away at the sea bed or beach
What is Attrition
Rocks in the backwash smash against each other. They break apart becoming smaller and more rounded
What is corrosion
Where the sea water dissolves certain types of rock
Define transportation
The movement of sediment within the sea by waves
Give the 4 types of transportation
Solution
Saltation
Suspension
Traction
Describe Traction
Pebbles and large sediment are rolled along the seabed
Describe Suspension
Small particles are carried in the water e.g sand and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves
What is solution
Minerals are dissolved in the sea water and are carried in solution. The load is therefore not visible. Load can come from cliffs made of chalk or limestone and calcium carbonate is carried along in solution
What is saltation
Load is bounced along the sea bed (small pieces of shingle or large sand grains). Currents cannot keep the larger and heavier sediment afloat fro long periods of time.
Describe longshore drift
Is the movement of water in the sea
The prevailing wind blows waves onto the costa at an angle, were they erode.
Tides than take the water and the eroded material back out to sea at right angles to the coast direction.
This means that the water and the material have moved along the coast.
The wind the blows them in again and tides out etc. and continues redoing until the LSD comes up against a natural or human structure that forces it to deposit
Define deposition
When the sea looses energy, it drops the sand, rock particles and pebbles it’s carrying. This is called deposition
Give some conditions needed for deposition to occur
Constructive waves
Shallow water
Little wind
Sheltered areas (bays)
What are concordat coastlines
Occur when the layers of different rock the lie parallel to the sea. As a result they are much straighter and have fewer landforms
What are Discordant coastlines
Occur when the layers of different rock types lie perpendicular to the sea. As a result thy create headlands and bays
How do Headlands and bays form
They form on discordant coastlines where the rock is perpendicular to the wave direction.
The roc is made up of alternating bands of soft and hard rock (clay and chalk).
The waves erode the soft rock made by hydraulic action causing the hard rock to jut out into the sea, making soft rock/bays more sheltered.
Give the 6 stages and description of the formation of a stump
CRACK
-Headlands attacked by hydraulic action, corrosion and attrition. Cracks begin to appear.
CAVE
-Cracks are widened to creates sea caves on either side of the headland
ARCH
-Two caves may join together to create an arch. Eventually the ref of the arch will collapse…
STACK
-Leaving a stack…
STUMP
-The stack continues to be eroded especially at the base. Eventually the stack collapses to leave a stump or a wave cut platform
CLIFF RETREATS
-The cliff goes through this process repeatedly causing it to retreat over many years.
Explain why deposition occurs at certain places along the coast
Because along the coast there is a variation of sheltered areas and constructive waves. When these occur and there is shallow water, the wave will loose energy and drop the material it’s carrying causing deposition
Beaches are one of the most common features of a coastline. They are made up of……………..material that has been……………… from elsewhere and later…………………by the sea. They can be made up of either…………or……………
Eroded Transported Deposited Sand Shingle
What is a spit
An accumulation of sediment with one end attached to the land and the other eating out across an estuary str into the sea.
Give 4 conditions needed for a spit to form
LSD
Strong prevailing wind
Line of coast changes
Sediment
Describe the life of a spit
The sit forms form an accumulation of sediment with one end attached to the land and the other eating out across an estuary str into the sea.
Eventually over time from LSD, this deposition will build up causing it to continually grow across. The hooked end is caused when the prevailing wind changes, pushing the sediment into a lightly different direction
What are sand dunes and how do they form
Sand dunes are small ridges or hill of sand found at the top of a beach, above the usual maximum reach of waves.
They form from wind blown sand that is initially deposited against an obstruction such as a bush, driftwood or a rock. As more sand parcels are deposited, the dune grows in size.
What are coral reefs made from
Hundreds of polyps
What are polyps
Mouth with tentacles
Give the 4 key conditions needed for cora reef to grow
Shallow water
- Sunlight can reach them
- Breaking waves give food and oxygen
Clean/clear water
- Sunlight can pass through
- Clean water don’t have as many nutrients, so nit much seaweed grows
Sunlight
- Algae gets energy from sun
- over 20˚C
Salinity
- Optimum levels of salt in water
- Freshwater kils coral
Give 3 types of coral reefs
Fringing reef - Lies close to shore
Barrier Reef - Borders shorelines but located further away
Atoll - Ring shaped coral reef, around an island
What are mangroves
Shrubs or small trees that grow in costal environments
They are tropical costal vegetation, commonly found in the inter tidal zone - the area that is above water at low tide and below it at hight tide
They are the only trees that are capable of thriving in salt water and have adapted to living in these conditions in a number of ways
Give 3 ways in which mangroves have adapted to their harsh conditions
Filtration system
- 90% salt altered out
- Excreted from old bark and leaves which drop off.
Strong roots
- Arial or butters roots
- Act as snorkels
- String and stable in silty and sandy soil
Oxygen
-Breathing tubes called pneumatophores
-
How do mangroves protect the coast against storm surges
The dense roots of the mangroves trap sediment flowing down the river. Tis helps stabilise the land and prevent erosion from waves and storms
Why are mangrove swamps a valuable ecosystem for the coastline
Because, not only do they help with costal protection, but also create their own environment supporting biodiversity for the local area
What is a hazard
Something that can cause harm to a person, object or the environment
What is a risk
The chance, high or low, that any hazard will actually cause harm
How do tropical storms form
The sun is directly over the equator, providing energy to the ocean
The warm ocean heats the air above it, causing it to rise rapidly
Water evaporates quickly from the hot surface of the ocean so the rising air contains great amounts of water vapour
The rising air starts to spin
As the air rises, it cools and condenses to form cumulonimbus clouds
The rapidly rising air creates an area of low pressure. The low pressure sucks air in causing very strong winds
Once the storm moves over the land, it looses energy and fades
What is soft engineering
Where the natural environment is used to help reduce costal erosion and river flooding
Give 3 soft engineering strategies
Beach nourishment
Dune regeneration
Marsh creation
What is beach nourishment and what are the pros and cons
Supplies sand to the shore to secure the beach from shore erosion (£3000 per km)
Pros:
- Blends in with existing beach
- Larger beaches appeal to tourists
Cons:
- Sand needs to be constantly replaced
- Sand has to be brought in from elsewhere
What is Dune regeneration and what are the pros and cons
Involves creating or restoring sand dunes
The vegetation on the dunes help make it stabilised and provide a barrier to absorb wave energy (£2000 per 100m
Pros:
- Helps maintain the ecosystem
Cons:
- Time consuming planting vegetation
- Less effective than hard engineering solutions
What is marsh creation and what are the pros and cons
Plant vegetation along beaches to stabilise the land
Pros:
- Stabilises mud flats
- Reduces the speed of waves
- Creates ne habitats for organisms
Cons:
- Fairly expensive
- Not useful when erosion rates are high because the marsh can’t then establish itself
