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Weathering

Weathering. D. Crowley, 2008. Weathering. To know how rocks are weathered. Shape & Size. Rocks are different shapes and sizes because they are changed by the conditions in their environment Rocks gradually wear away – this is known as weathering There are three types of weathering: -

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Weathering

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  1. Weathering D. Crowley, 2008

  2. Weathering To know how rocks are weathered

  3. Shape & Size • Rocks are different shapes and sizes because they are changed by the conditions in their environment • Rocks gradually wear away – this is known as weathering • There are three types of weathering: - • Physical weathering • Chemical weathering • Biological weathering

  4. Expanding • What happens to objects when they are heated (think about the particle model) • Heating an object causes it to expand • However water also expands as it freezes (turning into ice) – this is why putting a bottle of liquid in the freezer causes it to break / water pipes can burst during winter as the water within turns to ice • Watch the bursting bolt demo…

  5. Physical Weathering • Physical weathering is caused by changes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves… • Temperature - when a rock gets hot it expands a little, and when a rock gets cold it contracts a little. If a rock is heated and cooled many times, cracks form and pieces of rock fall away (this type of physical weathering happens a lot in deserts, because it is very hot during the day but very cold at night) • Watch the glass rod demo…

  6. Physical Weathering • Freezing and thawing – water expands when it freezes • If water gets into a crack in a rock and then freezes, it expands and pushes the crack further apart • When the ice melts later, water can get further into the crack • When the rock freezes again, it expands and makes the crack even bigger - this process of freezing and thawing can continue until the crack becomes so big that a piece of rock falls off

  7. Physical Weathering Freezing and thawing

  8. Physical Weathering • Wind, rain and waves – the wind can blow tiny grains of sand against a rock wearing the rock away and weathering it • The rain can lash against a rock and wear it away • Waves can crash against a rock and wear it away

  9. Chemical Weathering • Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it • Minerals in rocks may react with the rainwater, causing the rock to be weathered – this is chemical weathering • Some types of rock are easily weathered by chemicals, such as limestone and chalk • Some types of rock are not easily weathered by chemicals, such as granite and gabbro

  10. Chemical Weathering Chemical weathering

  11. Chemical Weathering • The burning of fossil fuels produces oxides of sulphur and nitrogen, causing rain to become more acidic (acid rain) • This type of acid rain reacts more quickly with rock minerals, weathering them more rapidly…

  12. Biological Weathering • Animals and plants can wear away rocks – this is biological weathering • Burrowing animals such as rabbits can burrow into a crack in a rock, making it bigger and splitting the rock • Plant roots can grow in cracks – as they grow bigger, the roots push open the cracks and make them wider and deeper, eventually causing pieces of rock to fall away • People can cause biological weathering by walking. Over time, paths in the countryside become damaged due to the boots wearing them away

  13. Biological Weathering Biological Weathering

  14. After Weathering • Transportation is the movement of rock fragments (this can be via strong winds; rivers; glaciers etc…) • Deposition occurs when pieces of rock sink to the bottom of a river bed / lake/ sea eventually forming sedimentary rocks… • This then completes our rock cycle…

  15. Rock Cycle

  16. Rock Bingo • Create a table as shown, and choose any 9 of the following words • Write these in your table, and cross them off if you hear them… • Sedimentary • Igneous • Metamorphic • Erosion • Transportation • Deposition • Minerals • Acid • Fossils • Crystals • Interlocking • Non-interlocking • Weathering • Particle theory • Melting • Compaction • Porous • Grains

  17. Rock Bingo Erosion • The wearing away of rocks • The process of breaking rocks up (via physical, chemical, or biological means) • The carrying of rock fragments • Process by which rocks can no longer be carried due to insufficient energy • A rock which lets water pass through it is • A rock type which cannot contain fossils as they have melted • Rocks which often contain fossils • Expansion due to heat can be explained by the • This type of rain increases the rate of chemical weathering Weathering Transportation Deposition Porous Igneous Sedimentary Particle theory Acid

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