Transcript Slide 1
Lesson 1: Rock types and erosion Lesson Objective: To know how different rock types affect coastlines and to be able to identify areas of hard or soft rock. UNIT 5 – COASTAL CHANGE AND CONFLICT I have flown over many different types of coasts. What types of coasts do you think I have seen? Can you describe this coast? S.Africa Can you describe this coast? Melbourne, Australia What about this one? And this? And this last one? What are your experiences of coastal areas? Coasts are unique, valuable and often threatened area where the sea meets the land. The coastline is an ever changing boundary zone between the land and the marine/sea environment. Coasts have long been valued in many ways. Why are coasts important? Varied nature and uses of the coast Uses of Coasts Aberdeen Port Heysham Nuclear Power Station Geology and Rock Type The most important feature of a coast is often the type of rock in the area. Some rocks are resistant to erosion, whereas other rocks are more easily eroded. • Resistant rocks= hard igneous rocks e.g. Granite and basalt • Fairly resistant= sedimentary rocks e.g. Sandstone, chalk and limestone • Least resistant= weak sedimentary rocks e.g. Clay and shale. These will erode fast. Task: Complete a hierarchy from MOST to LEAST resistant coastal rocks. Concordant and discordant coasts This is a DISCORDANT Coastline. This is where the coastline is made up of BOTH hard and soft rock. They are usually at right angles to the coast. This picture shows Swanage on the Dorset coast- it has a mixture of erosional features including headlands and bays which are there because of the alternating hard and soft rock types. Concordant and discordant coasts This is a CONCORDANT Coastline. This is where the coastline is made up of hard and soft rock that run parallel to the coastline. This means the rock erodes at different rates. This is a picture of Lulworth Cove on the Dorset Coast. Waves have cut through the narrow entrance to the cove and then rapidly eroded the softer rock behind it. MARINE EROSION (cliff foot) These can be remembered using the anagram CASH C = Corrasion (abrasion) – the waves throw pebbles and rocks against the cliffs, wearing them away A = Attrition – the pebbles and rocks are worn away as they crash against each other. S = Solution (corrosion) – the water itself is slightly acidic and can dissolve minerals such as calcium carbonate, which is in chalk and limestone. H = Hydraulic Action – the force of waves traps air in cracks …air pressure breaks off pieces of rock… How else can we remember these? The secret art of Coastal Kung Fu! Hydraulic Action: make punching movements with hand- demonstrates force of water hitting cliff. Abrasion/corrasion: make a throwing gesture with hands like you are throwing dealing cards very rapidly Attrition: make 2 fists, and then bring them towards each other, hitting each other, then open hand to resemble a stone breaking. Corrosion/solution: have arms out stretched in front of you, waving fingers, and moving arms downwards. Sound effect of something dissolving is needed. Erosion can also be SUB-AERIAL (cliff face) WEATHERING – the break down of rocks by frost, ice (physical) or water (chemical solution), or tree roots and/or rabbits (biological) MASS MOVEMENT – movement of rock material downslope, such as cliff collapse or landslides, usually after heavy rain Erosion Processes- task Complete the work sheet. You may use page 70-71 of the text book to help you but try not to use it. Extension make a starter activity for next lesson that will act as a recap for today’s learning. Plenary Exam Question Explain how rocks and waves shape the coastline (6)