6th Grade Chapter 15 Part 2


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6th Grade Chapter 15 Part 2

  1. 1. Chapter 4 Rocks
  2. 2. The Rock Cycle H.W. pg. 93 ques. 1-4 <ul><li>A rock is a mixture of minerals, rock fragments, volcanic glass, organic matter, and other natural materials. </li></ul><ul><li>All rocks slowly change through time, and the model that we use to show this slow change is called the rock cycle . </li></ul>
  3. 3. Rock Cycle <ul><li>As you can see the rock cycle shows 3 different types of rock: </li></ul><ul><li>Sedimentary </li></ul><ul><li>Metamorphic </li></ul><ul><li>Igneous </li></ul><ul><li>Also you see that all 3 types can be formed in a number of ways. </li></ul><ul><li>This shows that any rock can change into any of the three major rock types. </li></ul>
  4. 4. Igneous Rock <ul><li>Igneous rock forms when magma cools and hardens. </li></ul><ul><li>At certain within the Earth, the temperature and pressure are just right for rocks to melt and form magma. </li></ul><ul><li>Magma can be located at depths of 150km below the Earths surface. The temperature of this magma can range between 650- 1,200 o C, depending on their chemical compositions and pressures exerted on them. </li></ul>
  5. 5. Igneous Rock <ul><li>The reason that these rocks melt is because of heat that is formed in the Earth’s interior. </li></ul><ul><li>The heat comes from the decay of radioactive material inside the Earth. </li></ul><ul><li>Another source of this heat is actually heat that is left over from the formation of the planet, which was originally molten. </li></ul><ul><li>Since magma is less dense than the surrounding rocks it is forced upward toward the surface, like in a volcano. </li></ul><ul><li>When magma reaches the Earths surface and flows from volcanoes it is then called lava </li></ul>
  6. 6. Igneous Rock <ul><li>So magma is melted rock material composed of common elements and fluids. </li></ul><ul><li>As magma cools atoms and compounds rearrange themselves into new crystals called mineral grains . And rocks form as these mineral grains grow together. </li></ul><ul><li>So rocks that form from magma below the Earths surface are called intrusive. </li></ul><ul><li>These intrusive rocks stay underground until the land above them are removed, either by erosion of by physical means, and exposed to the surface. </li></ul>
  7. 7. Igneous Rock <ul><li>Intrusive rocks form at deep depths of the Earth. This causes the rocks to cool very slowly. </li></ul><ul><li>Slowly cooled magma will then produce very large mineral grains that we can see, within the intrusive rocks. </li></ul>
  8. 8. Igneous Rock <ul><li>Extrusive igneous rocks are formed by the cooling of lava on the surface of the Earth. </li></ul><ul><li>When lava cools on the surface it could be exposed to water and air. This causes the lava to cool quickly and does not allow large mineral grains to form. </li></ul><ul><li>Therefore extrusive igneous rock looks fine grained. </li></ul>
  9. 9. Metamorphic Rock <ul><li>Rocks that have changed because of changes in temperature and pressure or the presence of hot, watery fluids are called Metamorphic Rock. </li></ul><ul><li>These changes can be in the form of the rock or in its composition or both. </li></ul><ul><li>Metamorphic rocks can form from igneous, sedimentary or from other metamorphic rocks. </li></ul><ul><li>Ex: When you add heat and pressure to granite, the mineral grains are flattened and a metamorphic rock called gneiss is formed. </li></ul>
  10. 10. Granite & Gneiss
  11. 11. How to Classify Metamorphic Rock <ul><li>Metamorphic rocks can form from igneous, sedimentary, or other metamorphic rocks through their interaction with heat pressure and hot fluids. </li></ul><ul><li>We classify these rocks by their composition and texture. </li></ul><ul><li>First is Foliated rocks . A metamorphic rock is said to have foliated texture when mineral grains in the rock line up in parallel layers. </li></ul>
  12. 12. Metamorphic foliated rock <ul><li>Two examples of foliated rocks are slate and gneiss. </li></ul>
  13. 13. Non Foliated metamorphic Rock <ul><li>In non foliated metamorphic rock layering does not occur. The mineral grains grow and rearrange but do not form layers. </li></ul><ul><li>This produces a non foliated texture. </li></ul><ul><li>An example is when sandstone, a sedimentary rock composed of mostly quartz grains, is exposed to heat and pressure. </li></ul><ul><li>The quartz grains here grow in size and become interlocking like a jigsaw puzzle. </li></ul><ul><li>The resulting rock is called quartzite. </li></ul>
  14. 14. Non Foliated metamorphic Rock
  15. 15. Sedimentary Rock <ul><li>Igneous rocks are the most common rocks on Earth. However we don’t see them a lot because they are mostly beneath the Earths surface. </li></ul><ul><li>75% of the rocks that are exposed at the surface are sedimentary rocks . </li></ul><ul><li>Sediments are loose materials such as rock fragments, mineral grains, and bits and pieces of shell that have been moved by wind, water, or ice </li></ul><ul><li>These sediments come from already existing rock that were weathered or eroded. </li></ul><ul><li>Sedimentary rock forms when these sediments are pressed together by great pressure, or when minerals form in solution. </li></ul>
  16. 16. Stacked Rocks <ul><li>Sedimentary rocks often form in layers. The older layers are on the bottom layers because they were deposited first. </li></ul><ul><li>Sometimes these layers can be disturbed by the forces of nature. This will sometimes overturn the layered sedimentary rock and the oldest will no longer be on the bottom. </li></ul>
  17. 17. Conglomerate
  18. 18. <ul><li>Test on chapter 3 in one week!!!!!!!!!!!!! </li></ul>Test in One Week!!!!!