Coastal Change and Conflict Revision Summary Coastlines are all different!!! The type of rock at the coast affects the shape o f the coastline. Granite Basalt Limestone Chalk Sandstone Hard Igneous Rock Shale Clay Soft Sedimentary Rock Sedimentary Rock Describe how this coastline might have change in 50 years time. Explain the natural processes that contributed to its change Use diagrams to help. (6 marks) Coastlines where the geology alternates between strata (or bands) of hard rock and soft rock are called discordant coastlines. A concordant coastline has the same type of rock along the coastline. Concordant coastlines tend to have fewer bays and headlands. This is Lulworth Cove on the Dorset coast. It is a concordant coast. Make sure you can sketch this coastline and describe how Stair Hole will change in the future as it continues to erode. Key Terms to know and use: concordant, hydraulic action, corrosion, abrasion, attrition, sedimentary rock, headland, bay, limestone, chalk, sand, clay Lulworth Cove Stair Hole Discordant coast Task – draw this coast as it would be in 100 years time. Suggest some rock types for the grey, orange and brown rocks. Remember each of these 4 factors affect Coastal Erosion. The Fetch is the distance of water wind blows over before it reaches land. Dont forget to have a go at the wave Wave simulator Summer waves have: • A strong swash • Transport sand up the beach • Sand is deposited as a bank or beach berm. Winter Waves •They have strong backwash •This erodes sand from the beach •The sand is carried offshore by an underwater rip current •The sand is deposited out at sea, forming an offshore bar. At a river mouth, longshore drift pushes sediment out into the river. It is deposited forming a long neck of sng and shingle called a spit. A tombolo is where a beach grows out to meet an island –often produces when two longshore drift currents from different directions meet. Small bays can often be blocked by a bar of sand which grows across the mouth of the bay by longshore drift. Behind the bar a shallow lagoon forms. In the calm water behind a spit or bar salt marshes can form. As the salt marsh gradually gets colonised by plants it will eventually become new dry land. Sand dunes are created parallel to the shoreline when strong winds blow inland . Sand dunes are often stablised by tough plants like Marram grass Sea Level rise is due to A) The melting of Polar icecaps, Glaciers and the ice sheets of Greenland due to higher global temperatures. B) Warmer water taking up more space process know as Thermal Expansion. Diagram A Diagram B warmer water up more SPACE! takes The Maldives are a group of low lying islands in the Indian Ocean. Most are less that 1 meter above see level. Sea level rise is predicted to be around 1 cm a year so in 100 years the Maldives will be underwater. Problems include gradual decline of tourism on the islands creating poverty. Eventually all the islanders will become refugees. Factors leading to a Storm Surge Natural Tidal patterns Shallow sloping beaches and coastlines Storm Surge Low air pressure Large Waves Spring Tides Sea level rise Case Study In 1953, when there was a 5 meter storm serge in the North sea, over 300 people were killed in the UK and 1800 in the Netherlands in devastating flooding. http://www.metoffice.gov.uk/corporate/pressoffice/anniversary/floods1953.html Why Cliffs Collapse Marine processes •The base of the cliff is eroded by hydraulic action and abrasion, making the cliff face steeper. Sub-aerial processes •Weathering weakens the rock. This can be mechanical weathering like freezethaw action, or chemical weathering, like solution. •Heavy rain saturates the permeable rock making the rock heavier. Human Actions •Building and walking on top of the cliffs adds weight and pushes down on the weak cliff. Groynes – prevent longshore drift Revetments – break up incoming waves. Can be ugly and restrict beach access. Rock Armour – absorb wave energy, cheap and easy to build. Sea wall - reflects waves back. Expensive but can provide recreational facilities. Gabions – dissipate wave enery. They are cheap but not very strong Case Study - This is a picture of Barton of Sea, Dorset. Causes: Mass movement is the major cause of cliff erosion. But increasing bad weather, cliff foot erosion and water movement in the cliff all play a part. Human activity such as building on top of the cliff increases the risk of collapse. Impacts: Homeowners could lose their homes to the sea. Houses will fall and insurance may be impossible to get. Rapid cliff collapses are dangerous for people on top of the cliff and on the beach. Roads and other infrastructure (electricity/phone cables , gas and water pipes) are destroyed. Many people would say the erosion makes the area unattractive. Solutions: The people of Barton on sea want se defences but they are expensive and there is no agreement of which type of defence would work best. Managing the modern way – a Holistic approach Soft engineering solutions • Planting Vegetation to make cliffs more stable . £20 -£50 per square meter. • Beach nourishment; sand is pumped onto thje nbeach to increase its size. £500 - £1000 per square meter. • Offshore breakwaters; built using rip-raps they force waves to break befre reaching the the beach and cliff. £2000 per meter.