Weathering- the breakdown and decay of rock by natural processes , without the involvement of any moving forces.
Salt crystal growth- The spray from sea water lands on rock, the water evaporates, leaving salt behind . The salt crystals grow and create stress on rock, causing it to break down into smaller fragments.
Acid Rain- all rain is acidic and if air is polluted, can be very strong . When rain falls on rock it can react with weak minerals causing them to dissolve and the rock to decay .
Biological Weathering - Roots of vegetation can grow into cracks in a rock and split the rock apart.
Mass Movement- the downslope movement of material due to gravity.
Rock fall- one of the most sudden forms of mass movement. Rock fall occurs when fragments of rock weathered from a cliff face fall under gravity and collect at the base.
Slumping- Often happens when the bottom of a cliff is eroded by waves. The slope becomes steeper and the cliff can slide downwards in a rotational manner. Usually triggered by saturation due to rain, which lubricates the rock and makes it heavier. It’s visible how the weight added by rainwater and erosion by waves combine to cause the rotational slump.
Wave cut platforms are fairly flat, rocky areas at the bottom of cliffs. Waves erode coastline causing undercutting at the base of the slope. The notch gradually gets bigger, the rock above then looses its support and collapses, debris is washed away by waves and this is repeated; making the cliff slow retreat and get steeper. Diagram on next page.
Saturation by Rainfall Rotational Slump Erosion by waves
Headlands and Bays- always found together, a headland separates bays along a coastline. Their formation is affected by geology, Coastlines are made of different types of rock, the areas of weak, less-resistant rock erode quicker to become bays, resistant rock becomes headlands. Causing an indented coastline.
Wave undercut notch Wave-cut platform Waves Collapse happens Over time
Stack- isolated column of rock standing off the coast, once attached to land.
Stump- a collapsed stack.
Formation of erosional landforms:
Headlands gradually become eroded despite being made from resistant or hard rock. Waves bend around the coastline and erode both sides.
Joints or cracks or weak points erode quicker and small caves form both sides, as erosion occurs they join to make an arch.
More erosion with weathering makes the roof collapse and leaves an isolated stack- which slowly becomes undercut by wave erosion and collapses into a stump, visible only at low tide sometimes. In Dyroholaey, there’s an example of this (SE Iceland)
Longshore drift- material movement along a coastline.
Waves move towards the coast at an angle, as they break, swash carries material up and along the beach at the same angle. As the swash dies away, backwash and material fall at 90° because of gravity. Material goes in a zig-zag pattern. The prevailing wind is South Westerly and the backwash continues at 90°.
Longshore drift is continuous and can take a lot of a beach.
Fresh water and sea water are trapped behind the ridge as it forms.
Dunes could form at the back, hooked end or run along parallel to the coast. Strong winds and sea currents lead to a curved spit end.
Deposition begins at the bend Original coastline Cliffs Spit Bend in coastline Direction of Longshore Drift Mud and marsh in sheltered water Standing water colonised by Marsh plants. Eroded materials picked up by the waves Sediment accumulates as a ridge is built out to sea.
Durlston Bay near Swanage receded 12 metres between 1968 and 1988 ending up 25 metres from an apartment block called Purleck Heights. In 2000/01 severe storms and high energy waves led to a further 12 metres recession and put the building at rock.
In the UK, loss of property to cliff recession isn’t covered by insurance. In the USA, $80m per year is paid out by a national insurance programme.
High recession rates threaten the environment. Durlston Country Park also lies on the cliff top and is home to over 250 bird species. Puffins & Falcons rest on the cliff. Their habitats are threatened by recession of the cliff, which affects the rare species.
Open space will be left to prevent building damage.
The flooding will cause economic problems and high death rates.
The Environmental Agency predicts floods and monitors the weather.
Thames Estuary Case Study- on January 31st 1953 the worst natural disaster in living occurred. A tidal wave built up in the Atlantic coincided with the high spring tide. 307 people died and 40,000 people were displaced. Worst affected was Canvey Island where 58 people died and 160,000 acres were flooded.
As a result a new sea wall was repaired and replaced plus millions of pounds were spent on the Thames Estuary Barrier- the most expensive tidal barrier ever.
The Barrier will only work until 2030, but it’s hoped to be able to extend this to 2100.
In Bangladesh, the coastal embankment project has led to the building of several flood walls, 500 flood shelters were built although 10,000 were needed. Locals are learning about this and flood warning systems have been installed. In 1997, the Cox’s Bazaar area allowed 300,000 people to be evacuated. Only around 100 people died which was lower than before. Buildings now have to have flat roofs and an exterior stairway for people to escape.
Reasons to Protect the Coast:
Population Density- how many people could be displaced.
Trade- how much money lost.
History- risk of ruination of historic landmarks.
Tourism- economic loss; Agriculture- damage of land
Destructive waves have a weak swash and strong backwash, and are short in relation to their height. They’re also high in relation to length. Erosional and less that 1 metre in height.
Y- Wave cut platform
4. The geology of rock often affects how a coastline erodes; the softer or less resistant the rock, the quicker it erodes. The soft rock (clay etc.) erodes faster than the hard rock (granite etc.) and so a bay is slowly created as the soft rock recedes, the hard rock still remains sticking out, and so becomes a headland. The resistance of rock affects formation.
Groynes- a groyne prevents longshore drift and so allows a beach to form, however, a nearby coast would no longer have any sand deposited and so would recede instead.
Fetch- the greater the distance a wave has travelled, the more energy it has and therefore the more destructive, causing cliffs to recede more. A wave with a low fetch would build up a coast, but one with a high would do the opposite.
Rip Rap- absorb energy and look natural. They restrict access and can be expensive.
Sea wall- protects the base of a cliff, it can reflect wave energy; however, it can be expensive and looks unnatural and horrible.
Coastal flooding can be reduced by the creation of a barrier such as the Thames Estuary Barrier in London, which controls the amount of water in the river at any time. In Bangladesh, mangrove swamps have been created to buffer waves before the reach land and dissipates their energy and sea walls in Seaford (long concrete walls which reflect wave energy) can be used to stop the waves hitting the cliff face and eroding further.
Rip rap can also be used to absorb wave energy and make the impact lessen greatly, a collection of rocks looks natural and provides a barrier against wave erosion. Along Holderness’ coast, a groyne has been installed which lessened the cliff face land but protected many villages. Vegetating a slope also acts as a soft-engineering option to buffer the waves.
Kileder Water Reservoir in Northumberland carries 200bn litres and is surrounded by Kielder Forest. It was built between 1975 and 1981 and was opened in 1982. It’s the largest artificial lake in the UK and the largest artificial forest.
It took 2 years to flood and supploes Newcastle, Sunderland and Middlesborough. Tourists come to the reservoir to enjoy the wide range of leisure opportunities such as waterside parks.
Aquifers are deep layers of rock that hold water, this is extracted by drilling down to the rocks and pumping the water out.
The rocks of the North and South Downs store water like this, they get 750mm of rain and half goes in to the chalk. 400 bn litres of water is stored.
Work has been started for a 24bn litre storage reservoir and the capacity of the treatment plant is being doubled, this is to meet the demand for water in the area.
Water surplus and water deficit are dependant on how much water a place receives due to rainfall and how much it looses due to evaporation.
Places in the North are balanced, whilst places along the Equator receive less.
Some places receive more water than that lost which causes a surplus.
Some places have high rates of evaporation and transpiration that they loose more than they receive making a deficit. Some places have a lot of rainfall and high temperature and have no surplus, this is the cause with Africa.
Loss through broken pipes- leakages etc. mean water distribution is less efficient. Old pipes break and pollute drinking water.
Quality of water in the UK is monitored by the drinking water inspectorate. 1.7% of tests find water below quality according to the EUs ‘Water Framework Directives’
Nitrogen fertilisers can cause high levels of nitrogen to be poisonous.
Nuclear power plants pump waste water back into the environment.
The EU try to reduce fertilises which are nitrogen-based as they can lead to high nitrate levels, in 2007 the EU reported the chemical quality of water was good or very good in 76% of cases. In 2007, 0.4% were below.
Agriculture- fertilisers, pesticides and herbicides.
Domestic- waste, flushed things.
Industrial- nuclear waste
Others- litter, sports, swimming, dogs urine.
Birmingham is supplied by 3 pipelines from 3 reservoirs in the Elan and Claerwen valleys of mid-Wales more than 100km away. This is because of spatial variability. Most rain falls in the North and West of England but the most demand is in the S & E, water is transported to these places.
Costa Del Sol- places with a lot of seasonal variation suffer supply problems, rainfall in Costa Del Sol, Spain is low- in July and August it’s almost nil.
It’s in these months the demand increases, swimming pools and over 70 golf courses need watering.
In the places around the Mediterranean sea, water tends to fall in the winter season and the summer is a dry time.
There’s no new water to collect.
Dehydration and agriculture suffer.
No food for livestock.
Lack of hygiene.
Resorts lose business.
6 major reservoirs have been created including La Concepción with a capacity of 65 million metres cubed, a desalinisation plant was built in Marbella to 20 million m3. Another desalinisation plant in Mijas was opened in 2009.
Loss of water in the UK from the distribution centre is about 20%.
In London, the water distribution system was mostly constructed in the 1830s and 40s, and many of these have been in use since.
As demand has increased, water pressure has had to be increased to move water quickly through the system, many pipes can’t take the pressure and burst, the burst water mains are responsible for about 20% of London’s water.
Old pipes also rust and decay.
In the ‘90s a new ring main was built 40 metres below the surface and 80 kilometres of 2.5m diameter pipeline. £250 million were spent and leakage losses has been reduced.
In Mozambique, most domestic water is accessed by House connection, yard tap with 36%, and neighbour’s houses having 30%. Only 1/3 of the population has piped water.
About 900 million people suffer from water borne diseases, responsible diseases include Bilharzias, Cholera and typhoid. Over 300 million are supposed to have Bilharzias in LICs. Cholera is caught by faeces in water due to inadequate sewage and typhoid is caught by drinking infected water.
In HICs water is managed by:
Water meters in homes, 30% of homes have these and all new homes must have them. Owners pay for the amount of water they use in cubic metres.
It encourages people to be careful with how much water they use, in 2008 the cost was £1.60 per cubic metre.
Single flush toilets use 13 litres of water, now dual-flush toilets use only 6 for a full flush and 4 for a reduced flush.
A hippo bag added to a single flush toilet also saves one litre a time.
Industrial Water Management by:
Using new techniques
Agricultural Water Management by:
More modern, efficient systems.
Drip-feed and sprinklers use less water than irrigation channels and ditches. It’s estimated that drip systems are 90% efficient, with only 10% water being lost to evaporation. Sprinklers are 70% efficient, channels are 50%
Using appropriate technology like boreholes in Mozambique.
The Rural Water Supply Network aims to provide cost-effective boreholes (CEBs) that are appropriate to meet the needs of local communities. CEBs cost around $5k to $6k to install and are funded by the Dutch gvt.
In Kolkata, India, Sewage water is recycled for fish farming and agriculture. Sewage is piped into shallow lagoons which allow sunlight to reach the bottom to help algae and photosynthetic oxygen to grow.
Waste is also being used for farming.
Sewage is piped, sunlight promotes algae growth, aquatic plants use sunlight.
Eccentricity- Earth’s orbit oscillates very slightly between nearly circular and more elongated every 100,000 years. This is evident in the glacial/interglacial cycles of the same period. When more elongated, the earth is colder.
Tilt- earth spins around on an axis that is tilted from perpendicular to the plane in which the Earth orbits the sun. This causes seasons.
When the angle is high, the polar regions receive less solar radiation than normal in winter and more in summer. High tilt angle= glacial.