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Rocks and weathering

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Rocks and weathering

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Rocks and weathering

  1. 1. 1 of 42 © Boardworks Ltd 2008
  2. 2. 2 of 42 © Boardworks Ltd 2008
  3. 3. Useful substances from rocks What useful substances do we get from rocks? 3 of 42 © Boardworks Ltd 2008
  4. 4. Where do the rocks come from? We get many useful substances from rocks, such as building materials, metals, pigments and jewels. But where do we get the rocks themselves from? They come from the Earth’s crust. The Earth’s crust is the thin outer layer of the Earth. It is about 30km thick on land and only about 8km thick under the sea. crust mantle inner core outer core 4 of 42 © Boardworks Ltd 2008
  5. 5. What is the Earth’s crust made of? 5 of 42 © Boardworks Ltd 2008
  6. 6. Minerals and metals Many of the useful substances we get from the Earth’s crust are minerals, which contain metals. Here are the names and formulae of some of the most common minerals. mineral formula metal extracted from it Fe2O3 Al2O3 PbS TiO2 CuFeS2 haematite bauxite galena rutile chalcopyrite iron aluminium lead titanium copper 6 of 42 © Boardworks Ltd 2008
  7. 7. Identifying rocks: summary type examples description sedimentary metamorphic igneous sandstone and limestone marble and slate basalt and granite the softest rock type, containing layers and sometimes fossils usually harder than sedimentary rocks, containing thin layers and twisted fossils usually the hardest rock type, containing shiny crystals 7 of 42 © Boardworks Ltd 2008
  8. 8. Different rocks = different uses 8 of 42 © Boardworks Ltd 2008
  9. 9. 9 of 42 © Boardworks Ltd 2008
  10. 10. Pancake rocks in New Zealand These limestone rocks at Punakaiki in New Zealand are known as the Pancake Rocks. How do you think they were formed? 10 of 42 © Boardworks Ltd 2008
  11. 11. What are sedimentary rocks? limestone chalk sandstone 11 of 42 © Boardworks Ltd 2008
  12. 12. Properties of sedimentary rocks What are the properties of sedimentary rocks?  Sedimentary rocks often have layers showing the deposition of sediment at different time periods.  Sedimentary rocks are made of lots of small grains. These grains are weakly held together so the rocks are often porous and may be soft and crumbly.  Sedimentary rocks often have fossils trapped within them. 12 of 42 © Boardworks Ltd 2008
  13. 13. Rocks and weathering Why are rocks all different shapes and sizes? 13 of 42 © Boardworks Ltd 2008
  14. 14. What is weathering? Rocks are different shapes and sizes because they are changed by the conditions in their environment. The breakdown of rocks into smaller fragments is called weathering. Eventually the fragments become soil. Can you think of anything that could cause weathering? Rocks can be weathered by temperature change, water, frost and even plants and animals. 14 of 42 © Boardworks Ltd 2008
  15. 15. Types of weathering Which type of weathering is caused by each of these:  temperature change  acid rain  plants and animals? There are three types of weathering:  physical weathering  biological weathering  chemical weathering. 15 of 42 © Boardworks Ltd 2008
  16. 16. What is chemical weathering? Slow chemical weathering  Rainwater is naturally a weak acid because carbon dioxide in the air reacts with rainwater to form carbonic acid.  This weakly acidic rain reacts with minerals in rocks and slowly wears them away. Rapid chemical weathering  The burning of fossil fuels produces oxides of sulphur and nitrogen, which make rainwater more acidic.  Acid rain reacts quickly with minerals, so the rocks get weathered more rapidly. 16 of 42 © Boardworks Ltd 2008
  17. 17. Examples of chemical weathering How has chemical weathering affected these rocks? 17 of 42 © Boardworks Ltd 2008
  18. 18. Which type of weathering? 18 of 42 © Boardworks Ltd 2008
  19. 19. Acid and carbonate When a carbonate reacts with an acid, it gives off carbon dioxide gas. How could you test the gas given off, to confirm that it is carbon dioxide? What would you observe in this test? carbon dioxide limewater 19 of 42 © Boardworks Ltd 2008
  20. 20. Acid and carbonate The products of the reaction between a carbonate and an acid are a salt, carbon dioxide and water. Calcium carbonate is a substance that is naturally found in the shells of sea creatures and snails. What salt do you think will be produced by the reaction of hydrochloric acid and calcium carbonate? calcium carbonate calcium chloride hydrochloric acid carbon dioxide + +  + water 20 of 42 © Boardworks Ltd 2008
  21. 21. Reaction of carbonates 21 of 42 © Boardworks Ltd 2008
  22. 22. 22 of 42 © Boardworks Ltd 2008
  23. 23. Erosion As a rock is weathered, pieces of it fall off. This is called erosion. They will then be transported away by water, wind or glaciers. by water by wind by glacier 23 of 42 © Boardworks Ltd 2008
  24. 24. Transportation by water 24 of 42 © Boardworks Ltd 2008
  25. 25. Rock changes during transportation 25 of 42 © Boardworks Ltd 2008
  26. 26. What is deposition? Deposition occurs after erosion and transportation. This is the process that occurs when pieces of weathered rock sink to the bottom of the river bed or sea, forming sediment. Eventually this sediment gets so squashed down that it forms new rock, called sedimentary rock. 26 of 42 © Boardworks Ltd 2008
  27. 27. Transportation by wind Rock particles being transported by the wind cause erosion. Wind erosion has two major effects:  Small particles picked up by the wind are deposited in new places. For example, this is how sand dunes are formed.  When the particles are suspended in the air they can hit objects and cause them to chip and wear down (think of how sand grains sting when the wind blows them against your skin at the beach.) 27 of 42 © Boardworks Ltd 2008
  28. 28. Transportation by glacier A glacier is a mass of ice that gradually moves overland. As the glacier moves, the stones and rocks in its path become incorporated into the base. The forward motion of the glacier causes the trapped rocks to rotate, scrape and grind along the ground. This friction weathers the landscape and causes valleys and fjords to form. Over time the smaller pieces of rock are carried into the melt water streams that surround the glacier, where they are redeposited on the ground. 28 of 42 © Boardworks Ltd 2008
  29. 29. After weathering: true or false? 29 of 42 © Boardworks Ltd 2008
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  31. 31. Glossary 31 of 42 © Boardworks Ltd 2008
  32. 32. Anagrams 32 of 42 © Boardworks Ltd 2008
  33. 33. Multiple-choice quiz 33 of 42 © Boardworks Ltd 2008

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