Costal landscapes in the UK

define mechanical weathering

The breakdown of rock without changing its chemical composition

Give an example of mechanical weathering and explain it

Freeze-thaw weathering

It happens when the temperature alternate above and below zero Celsius

1. Water enters rocks that has cracks e.g granite

2. When the water freezes it expands which puts pressure on the rock

3. When the water thaws it contacts which releases the pressure on the rock

4. Repeated freezing and throwing widen the crack and caused the rock to break up

define chemical weathering

Is the breakdown of rock by changing its chemical composition

Give an example of chemical weathering and explain it

Carbonation

which happens in warm and wet conditions

1. Rainwater has carbon dioxide dissolved in it, which makes a weak carbonic acid

2. Carbonic acid reacts with the rock that contains calcium carbonate e.g carboniferous limestone so the rocks are dissolved by rainwater

define mass movement

When material falls down a slope

How does mass movement happen?

Mass movement happens when the force of gravity acting on the slope is greater than the force supporting it, causing the coast to retreat rapidly.

• It is more likely to happen when:

the material fills with water, and the water acts as a lubricant

water makes the material heavier

• When the material shifts, it can

create a scarp (a steep cut in the side of the slope)

Define deposition

dropping of material

define swash and backwash

Swash = water moving up the beach

Backwash = water moving down the beach

Can waves only be destructive?

no as waves can be destructive and constructive

What are the characteristics needed for a destructive wave?

• High frequency

• high and steep waves

• the backwash is more powerful than their swash so material is removed

What are the characteristics needed for a constructive wave?

• low frequency

• low and long waves

• swash is more powerful than the backwash the material is deposited

What are the three processes of erosion waves use to wear away the coast?

Hydraulic power - waves crashed against a rock and compress the air in the cracks. This puts pressure on the repeated compression widen the crack and causes bits of rock to break off

Abrasion - eroded particles in water scrape and rub against rock removing small pieces

Attrition - eroded particles in the water collide break into small pieces and become more rounded

How can material be transported along the coast?

By longshore drift

Describe the process of longshore drift

1. Waves follow the direction of the prevailing wind

2. They usually hit the coast at an oblique angle

3. The swash carries material up the beach in the same direction as the waves

4. The backwash, then carries material down the beach at right angles back towards the sea

5. Overtime materials zigzags along the coast

What are the four processes of transportation?

Traction - large particles like boulders are pushed along the sea bed by the force of water

Suspension - small particles like silt and clay are carried along in the water

Saltation - pebble sized particles are bounced along the sea bed by the force of water

Solution - soluble materials dissolve in the water and are carried along

What are the two types of coastlines?

Concordant - the alternating band of hard and soft rock are parallel to the coastline

Discordant - made up of alternating bands of hard and soft rock at right angles to the coast

Characteristics and formation of landforms resulting from erosion

Headlands and bays

cliffs and wave cut platforms

cave arches and stacks

How does rock type geological structure influence the erosional landforms that develop on a coast line?

• Hard rocks like granite take a long time to erode, while softer rocks like sandstone erode more quickly.

• Rocks with lots of joints and faults erode faster.

How are headlands and bays formed?

Headlands and bays form along discordant coastlines, where bands of rock run at right angles to the coast. The less-resistant rock erodes faster through processes such as hydraulic action and abrasion, forming bays with gentle slopes. The more-resistant rock erodes more slowly and therefore sticks out into the sea as a headland with steep sides. Over time, differential erosion creates a coastline with alternating headlands and bays.

How are caves formed?

Waves crash into the headlands and enlarge the cracks mainly by hydraulic power and abrasion. Repeated erosion and enlargement of the cracks causes a cave to form.

How does a cave become an arch?

Continued erosion deepens the cave until it breaks through the headland to form an arch.

How is a stack formed?

Erosion continues to wear away the rock supporting the arch, until it eventually collapses which forms a stack an isolated rock that’s separate from the headland

Describe the formation of a wave cut platform

• Waves cause most erosion at the foot of the cliff, forming a wave-cut notch which is enlarged over time.

• Repeated erosion causes the rock above the notch to become unstable and eventually collapse.

• The collapsed material is washed away, and a new wave-cut notch begins to form.

• After repeated collapses, the cliff retreats, leaving a wave-cut platform.

Characteristics and formation of landforms resulting from deposition 

Beaches

Sand dunes

Spit and bars

describe how a sand beach is formed?

Sand beaches are created by low energy waves and are flat and wide sand particles are small so the weak backwash can move them down the beach creating a long gentle slope

Describe how a shingle beach is formed

Single beaches are created by high energy waves and a steep and narrow sand particles are washed away but largest shingle is left behind the shingle particles built up to create a steep slope

Describe how spits are formed

• Spits form at sharp bends in the coastline.

• Longshore drift transports sand and shingle past the bend and deposits it in the sea.

• Strong winds and waves can curve the end of the spit, forming a recurved end.

• The area behind the spit is sheltered from waves, so material accumulates and plants are able to grow.

• Over time, the sheltered area can become a mudflat or salt marsh.

Describe how bars are formed

1. A bar forms on a spit joins two headlands together

2. The bay between the headlands get cut off from the sea

3. This means a lagoon can form behind the bar

4. Offshore bars can form if the coast has gentle slope

   friction with sea beds causes waves to slow down and put settlement offshore creating a bar that is not connected to the coast

Describe how sand dunes are formed

1. Sand dunes form when sand deposited by longshore drift is move up the beach by the wind.

2. Obstacles (e.g. driftwood, plants) cause wind speed to decrease, so sand is deposited and forms small embryo dunes.

3. Embryo dunes are colonised by plants (e.g. marram grass). The roots of vegetation help stabilise the sand, allowing more sand to accumulate. This creates fore dunes, which develop into mature dunes. New embryo dunes form in front of the older, stabilised dunes.

4. Dune slacks (small pools) can form in the hollows between dunes.

How can coastlines be managed

By hard + soft engineering and managed retreat

Define hard engineering

man-made structures built to control the flow of sea and reduce flooding and erosion

Define soft engineering

schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion erosion

Four examples of hard engineering

1. Sea wall

2. Gabions

3. Rock armour

4. Groynes

Sea wall give the description and advantages + disadvantages

Description

• A wall made out of material like concrete that reflects waves back to sea

Advantage

• It prevents erosion of the coast. It also acts as a barrier to prevent flooding.

Disadvantage

• It creates a strong backwash that erodes under the wall and is expensive to build and maintain

Gabions give the description and advantages + disadvantages

Description

• A wall of wire cage is filled with rocks usually built at the foot of cliffs

Advantage

• absorb wave energy and so reduce erosion they are cheap and easy to build

Disadvantage

• they are ugly to look at and the wire cages can corrode over time

Rock armour give the description and advantages + disadvantages

Description

• boulders that are piled up along the coast it’s also sometimes called riprap

Advantage

• it absorbs wave energy reducing erosion and flooding it’s a fairly cheap defence

Disadvantage

• boulders can be moved around by strong waves so they need to be replaced

Groynes give the description and advantages + disadvantages

Description

• wooden or stone fences that are built at right angles to the coast they trap material transported by longshore drift

Advantage

• they create wider beaches which slow the waves this gives greater protection from flooding and erosion. They’re a fairly cheap defence.

Disadvantage

• they starve beaches further down the coast of sand making them narrower beaches which don’t protect the coast very well leading to greater erosion

two examples of soft engineering

1. Beach nourishment and reprofiling

2. Dune regeneration

Beach nourishment and reprofiling give the description and advantages + disadvantagessand

Description

• Sand and shingle from elsewhere (e.g seabed) all from lower down the beach that added to the upper part of beaches

Advantage

• It creates wider beaches which slow the waves this give greater protection from the flooding and erosion

Disadvantage

• Taking material from the sea that can kill organisms like sponge and coral it’s a very expensive defence. It has to be repeated

Dune regeneration give the description and advantages + disadvantages

Description

• Creating or restoring sand dunes by nourishment or by planting vegetation to stabilise the sand

Advantage

• Dunes create a barrier between land and sea and absorb wave energy, prevent flooding and erosion. stabilisation is cheap

Disadvantage

• The protection is a limited to a small area. Nourishment is very expensive

Managed retreat give the description and advantages + disadvantages

Description

Removing current defences and allowing the sea to flood the land behind

Advantage

• Overtime the land will become marshland which then protects the land behind it from flooding erosion. It’s cheap and easy. It doesn’t need maintaining the marshland can also create new habitats for plants and animals.

Disadvantage

• can cause conflicts e.g flooding farm line affects the livelihood of farmers and saltwater can have a negative effect on existing ecosystems