coastal landscapes in the Uk

Rock is broken down by MECHANICAL and CHEMICAL WEATHERING

1. Mecahnical weathering is the breakdown of rock without changing its chemical composition. 

• It happens when the temperature alternates above and below 0 degres c 
• Water gets into the cracks 
• when the water freezes it expands, which puts presure on the rock 
• when the water thaws it contracts, which releases the preseure on the rock 
• Reaped freezing and thawing widens the cracks and causes the rock to break up 

2. Chemical weathering is the breakdown of rock by changing its chemical composition. 

• Rain water has carbon dissolved in it a weak carbonic acid 
• Carbonic acid reacts with the rock that contains calcium carbonate, e.g carboniferous limestone, so the rocks are dissolved

MASS MOVMENT is when material falls down a slope 

• Mass movement is the shifting of rocks and loose material down a slope e.g a cliff
• mass movement cause coasts to ratret rapidly 
• They're more likely to happen when material is full of water, it acts as a lubricant

You need to know about the three types of mass movement:

• Slides: materal is in a straight line

• Slumps: material moves with a roatation 

• Rockfalls: material breaks up and falls down slope 

Waves wear away the coast using THREE PROCESSES OF EROSION

• Hydralic power--waves crash against rocks and compress the air in the cracks. This puts pressure on the rock. Repeated compression widens the cracks and makes bits of rock break off.
• Abrasion--eroded particals in water scrape and rub against rock, removing small pieces.
• Attrition--eroded particals in water smaash against each other and break into smaller fragments. Their edges also get rounded off as they rub together.

• The waves that carry out erosinal processes are called destructive waves: 
• Destructive waves have a high frequency (10-14 waves per minute).
• They are high ans steep.
• Their backwash (the movement of the water back down the beach) is more powerful  than their swash (the movement of water up the beach). This means material is removed from the coast. 

Waves erode cliffs to form WAVE--CUT PLATFORMS

• Waves cause most erosion at the foot of the cliff 
• This forms a wave--cut notch, which if enlarged as erosion continues 
• The roch above the notch bacomes unsstable and eventually collapses 
• Repeated collapsing reasults in the cliff retreating 
• A wave--cut platform is the platform that is left behind as the cliff retreats 

HEADLANDS AND BAYS FORM WHERE EROSION RESISTACE IS DIFFERANT 

• Soft rocks or rocks with loads of joints have low resistance to erosion. Hard rocks with solid structure have a high resistance to erosion.
• Headlands and bays form where they are alternating bands of resistant and less resistant rock along a coast.
• The less resistant rock (e.g clay) is eroded quickly and this forms a bay-- bays have a steep slope.
• The resistant rock (e.g chalk) is eroded more slowly and its left jutting out, forming a headland -- headlands have steep sides.  

HEADLANDS ARE ERODED TO FORM CAVES, ARCHES AND STACKS. 

• Headlands are usall made of resistant rocks that has weaknesses like cracks.
• Waves crash into the headlands and enlarge the craacks-- mainly by hydralic power and abrasion.
• Repeated erosion and enlargement of the cracks causes a cave to form.
• Continued erosion deepens the cave until it breaks through the headland-- forming an arch e.g durdle door in dorset 
• Erosion continues to wear away the rock supporting the arch, until it eventually collapses.this forms a stack -- an isolated rock that is seperated from the headland e.g Old Harry in Dorset. 

TRANSPORTATION IS THE MOVEMENT OF MATERIAL 

Material is transported along coasts by a processcallled longshore drift: 

• Waves follow the direction of the prevaling (most common) win. 
• They usually hit at an oblique angle (any angle that is not  a right angle).
• The swash carries the material up the beach, in the same direction as the wind . 
• The backwash carries the material back down the beach at right angles, towards the sea.
• Over time, material zigzags along the coast. 

There are four other processes of transportation: 

Traction: large partiicales like boulders are pushed along the sea bed by the force of the water.

Saltation: peble sized particles are bounced aalong the sea bed by the force of the water.

Suspentsion:small particles like silt and clay are carried along in the water 

Solution: soluble materials dissloved in the water and are carried along. 

DEPOSITION IS THE DROPPING OF MATERIAL

• Deposition is when material  being carried by the sea water is  dropped on th coast. It occurs when water carring sediment  slows down so that it isn't moving fast enough to carry so much sediment. 
  
• Coasts are built up when the amount of deposition is greater than the amount of erossion.
• the amount of material that's deposited on an area of coast in increased when: 

There's alot of erosion elsewhere on the coast, so there is lots of material avaliable.

There is lots of transportation of material into the area. 

• Low energy waves (i.e. slow waves) carry material to the coast but they're not strong enough to take a lot os material away -- this means there's lots of deposition and very little erosion 

Waves that deposit more material than they erode are called constructive waces. 

• Constructive waves low frequency (6--8 waves per minute 
  
• They're low and long 
• The swash is more powerful and it carries material up the coast 
• the backwash is weaker and it doesn't thake a lot of material back down the coast. This means material is depostied on the coast. 

DEPOSITED SEDIMENT FORMS SPITS 

• Spits form at sharp bends in the coatsline, e.g. at a rivers mouth.
• 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 sheltered area behind the spit is protected from waves -- lots of the material accumalated in this area, which means plants can grow there. 
• Over time. the sheltered area can become a mud flat or a salt marsh.    

DEPOSITED SEDIMENT FORMS BARS: 

• A bar is formed when a spit joins two headlands together.
• The bar cuts of the bay between the headland and the sea. 
• This means a lagoon can form behind the bar.

DEPOSITED SEDIMENT FORMS SAND DUNES: 

• Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind. 
• Obsticals (e.g. driftwood) cause wind speend decrease sos and is deposited. This  sand is colonised by plants and grasses. The vegatation stabilises and encourages more plants to grow there, forming smaall dunes called  embryo dunes.
• Over time, the oldest dunes migrate inland as mewer embryo dunes are formed. These mature dunes can reach heights of up to 10m. 

THE DORSET COAST HAS  MANT EXAMPLE OF COASTAL LANDFORMS: 

• Durdle door: 
• Durdle door is a great example of an arch. Erosion by waves opened up a crack in the limestone headland, which became a cave and than developed into an arch. 
• Lulworth cove : 
• Lulworth cave is a small bay formed after a gap was eroded in a band of limestone. Behind the limestone is a band of clay, which has been eroded away to form the bay. the same is starting ot happen at Stair Hole further west along the coast.
• Chesil beach: 
• Chesil beach ia a tombolo (a type of bar) formed by longshore drift. It joins the Isle of Portland to the mainland. Behind Chesil beach is a shallow lagoon called The Fleet Lagoon. 
• Swanage bay, The Foreland and Studland bay: 
• There are two bays with bbeaches called swanaage bay and studland bay. They're areas of  softer rock standstrone and clay). In between then is a headlland called The Foreland made from a band of harder rock  (chalk). the end of the headland has become a stack called Old Harry and a stump ( a collapsed stack) called Old Harry's Wife, which is no longer there because it has continued to be eroded. 

HARD ENGINEERING IS MAN-MADE STRUCTURES BUILT TO CINTROL THE FLOW OF THE SEA AND REDUCE FLOODING AND EROSION.

• Sea wall: what is it- a wall made out of a  hard material like concrete that reflects waves back to sea.  Benefits- It preventss erosion of the coast. It also  has a barrier to prevent flooding. Costs- It creats a strong backwash, which erodes under the wall. Sea walls are very expensive to build and to maintain and they don't give a natral look to the coastline.
• Gabions: What is it- A wall of wire cages filed with rocks usually buili at the bottom of cliffs. Benifits- The gabions absorb wave energy and so erduce erosion. They're cheap and easy to build. Costs- They're ugly to look at and the wire cages can corrode over time.
• Rock armour: what is it- Boulders that are piled up along the coast. (it's also sometimes caalled a rip-rap). Benefits- the boulders absorde wave energy and so reduce erosionand flooging. it's a fairly cheap defence. costs- Boulders can be moved around by strong waves, so they need to be replaced. 
• Groynes: What is it- Wooden or stone fences that are built at right angles to the coast. They trap material transported ny longshore drift. Benefits- They creat wider beaches which slow the waves. This give greater protection from flooding and erosion. They are fairly cheap. cost- They starve beaches further dowwn thee coast of sand, making them narrower. Narrower beaches don't protect the coast as well, leaading to greater erosion and floods. 

SOFT ENGINEERING IS SCHEMES SET UP USING THE KNOWLEGE OF THE SEA AND IT'S PROCESS TO REDUCE THE EFFECT OF FLOODINGAND EROSION. 

• Beach nourishment and reprofilling: What is it- Sand and shingle from elsewhere (e.g. the seabed) or from lower down the beach that's added to the upper part of the beaches. Benifits- It creats wider beaches which slowa waves. This gives greater protection from flooding and erosion. Costs- Taking material from the seabed can kill organisms like sponges and coral. It's very expencive. It has to be replaced,
• Dune regeneration: What is it- Creating or restoring sand dunes by either nourishment or by planting vegetation to stabalise the sand. Benefits- Sand dunes provide a barrier between the land and the sea. Wave energy is absorbed which prevents flooding and erosion. Stablisation is cheap. Costs- The protection is limated to a small area. Nourishment is very expensive. 

ANOTHER OPTION IS JUST  TO DO NOTHING - MANAGE RETREAT.

• Manage retreat (also called coastal realignment) involves removing current defences and allowing the sea to flood the land behind.
• Over time the land will become marshlaand, which then protects the land from flooding and erosion.
• It is a cheap and easy stratagy, and it doesn't need maintaining. The marshland can also creat new habitats for plants and animals. 
• Because land is lost to sea, choosing areas to flood can cause conflicts, e.g. flooding farmland would effect livelihood of farmers. The sa;twaater can also have a nehative effect on existing ecosysems