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Coasts

Coasts. By Sazjaz97. Types of Weathering. I n these next few slides I will be talking about different types of weathering that force the rocks to come apart and break down. There are four main types of weathering. These are: Biological Weathering Chemical Weathering

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Coasts

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  1. Coasts By Sazjaz97

  2. Types of Weathering In these next few slides I will be talking about different types of weathering that force the rocks to come apart and break down. There are four main types of weathering. These are: • Biological Weathering • Chemical Weathering • Freeze-Thaw Weathering • Onion-Skin Weathering All of these help to break down the rock which makes the rock weaker and therefore easier for waves to erode.

  3. Biological Weathering Biological weathering is caused by the activities of living organisms. An example of biological weathering is were seeds manage to fall into the cracks and joints in the rock and then they slowly force the rock apart. The moisture from the sea helps the seeds grow into a small plant or tree. Hence, the roots will gradually develop and force the cracks to widen and therefore the rocks will eventually fall apart. Also, biological weathering is were small creatures such as moles and even earthworms can help to break down the rock. However saying this, tree roots are probably the most significant because they are capable of widening the rocks. Plants can also give off organic acids that help to break down the rock chemically.

  4. Chemical Weathering Chemical weathering is when chemicals break down the rock to form smaller ones. For example, everyday rain water that contains acid, helps to make the rock crumble and rot away. This is called carbonation. Others types of chemical weathering are hydrolysis (breakdown by water such as the sea), hydration (breakdown by the absorption of water ) and finally oxidation (breakdown by oxygen in the air and water). Water and heat generally make chemical weathering happen faster.

  5. Freeze-Thaw Weathering Freeze-Thaw weathering is very common in mountainous and glacial environments. Freeze-thaw is the cause of water as it begins to freeze. As water in a joint freezes, it expands in volume by 9%. This creates great pressure on the rock, causing the joint to enlarge. After many cycles of freeze-thaw the rock slowly begins to break off.

  6. Onion-Skin Weathering Onion-skin weathering is when the rock is constantly heated and cooled. When the rock is heated it begins to expand and when it cools it contracts. Continual expansion and contraction causes it to peel off like onions. Onion-skin weathering is very common in deserts because they are warm by day but cool at night.

  7. Erosion Erosion means to wear away the rock. There are four main types of erosion: • Hydraulic Action:- This is when the force of the water wears away the rock. • Abrasion:- This is a pebble sliding against the rock like a sand paper action to wear it away. • Attrition:- This is when pebbles collide against the rock and hit each other cracking the rocks surface. • Corrosion:- This is the acid in the salt water slowly starting to dissolve the rock.

  8. Headlands and Bays • A headland is an area of hard resistant rock which protrudes out into the sea. • A bay is a soft peace of rock that erodes away easily by hydraulic action. • Hydraulic action still erodes the headland however very slowly. It forms a crack, then a cave, then an arch, a stack and finally a stump.

  9. Wave Cut Platform A wave cut platform is were waves erode cliffs by the process of hydraulic action. The waves then create a gap in the headland called a notch which weakens the cliff. The cliff eventually falls and the bottom of the notch will have become a wave cut platform. If this process is constantly repeated the wave cut platform will become bigger and able for people to walk on.

  10. Deposition Deposition is the is the laying down of sediments (materials from eroded cliffs). It happens when there is a longshore drift. The materials eventually form a spit which leans out over the coast. This creates another form of land. Therefore the fallen cliffs (were a peace of land has gone) has made another piece of land in the form of a spit.

  11. Quick Quiz • Which one of these is not a type of weathering? (Please circle one). • Name one type of chemical weathering... _____________ 3. Where is freeze-thaw said to be common? _____________ 4. Where is onion skin weathering said to be common? ____________ 5. What is the drift called in order for deposition to happen?_____________________

  12. Thank you for watching and I hope you enjoyed my PowerPoint.

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